JP2017220577A - Photo-detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-detection device having a novel configuration.SOLUTION: A photo-detection device according to an embodiment has a plurality of detection cells. Each detection cell has: a source region and a drain region formed on a semiconductor substrate; a gate insulating layer on the semiconductor substrate; and a transparent gate electrode on the gate insulating layer. The gate insulating layer has a photoelectric conversion layer that contains a first photoelectric conversion material and a second photoelectric conversion material having different absorption peaks from each other. Each detection cell outputs an electric signal that is generated by light incidence to the photoelectric conversion layer via the transparent gate electrode and that corresponds to a change in dielectric constant of the photoelectric conversion layer, from one of the source region and the drain region.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a light detection device.

  Conventionally, a light detection element is used in a light detection device, an image sensor, or the like. A typical example of the light detection element is a photoelectric conversion element such as a photodiode or a phototransistor. As is well known, light can be detected by detecting a photocurrent generated in a photoelectric conversion element by light irradiation.

  Patent Document 1 below discloses a thin film transistor (TFT) having an organic film in which a predetermined compound is dispersed in an organic polymer as a gate insulating film in FIG. As the predetermined compound constituting the organic film, a compound whose polarization state is changed by light irradiation is selected. In the thin film transistor disclosed in Patent Document 1, when the gate insulating film is irradiated with light, the dielectric constant of the gate insulating film changes. Therefore, the current flowing between the source and the drain changes due to the light irradiation to the gate insulating film. Patent Document 1 describes that such a thin film transistor can be used for an optical sensor.

JP 2011-60830 A

  Provided is a light detection device having a novel structure.

  According to certain non-limiting exemplary embodiments of the present disclosure, the following is provided.

  Each of the gate insulating layers includes a plurality of detection cells each having a source region and a drain region formed in a semiconductor substrate, a gate insulating layer on the semiconductor substrate, and a transparent gate electrode on the gate insulating layer. Has a photoelectric conversion layer including a first photoelectric conversion material and a second photoelectric conversion material having absorption peaks different from each other, and each of the plurality of detection cells has light to the photoelectric conversion layer via the transparent gate electrode. An optical detection device that outputs an electric signal corresponding to a change in dielectric constant of the photoelectric conversion layer caused by incidence of light from one of the source region and the drain region.

  Inclusive or specific aspects may be realized in an element, device, apparatus, system, integrated circuit or method. In addition, comprehensive or specific aspects may be realized by any combination of elements, devices, apparatuses, systems, integrated circuits, and methods.

  Additional effects and advantages of the disclosed embodiments will become apparent from the specification and drawings. The effects and / or advantages are individually provided by the various embodiments or features disclosed in the specification and drawings, and not all are required to obtain one or more of these.

  According to one aspect of the present disclosure, a photodetection device having a novel configuration is provided.

FIG. 1 is a schematic cross-sectional view illustrating a cross section of an exemplary photodetection device according to the first embodiment of the present disclosure. FIG. 2 is a diagram schematically illustrating an exemplary circuit configuration of the photodetection device 1000. FIG. 3 is a diagram showing an example of an absorption spectrum of C ₆₀ obtained by transmission measurement. FIG. 4 is a schematic cross-sectional view showing the gate insulating layer 23 and its periphery in the light detection structure 100A. FIG. 5 is a schematic cross-sectional view showing another example of the configuration of the photoelectric conversion layer 23p. FIG. 6 is a diagram showing an example of an absorption spectrum related to a bulk heterojunction structure of tin naphthalocyanine and C ₆₀ . FIG. 7 is a diagram showing an example of an absorption spectrum of subphthalocyanine represented by the general formula (4) obtained by transmission measurement. Figure 8 is a diagram illustrating an exemplary absorption spectrum of the layer containing the subphthalocyanine and C _60. FIG. 9 is a graph showing a typical example of the photocurrent characteristic in the photoelectric conversion layer 23p. FIG. 10 is a schematic cross-sectional view illustrating a cross-section of the light detection device according to the second embodiment of the present disclosure. FIG. 11 is a schematic cross-sectional view illustrating a modified example of the light detection device according to the second embodiment of the present disclosure. FIG. 12 is a schematic cross-sectional view showing a laminated structure in the sample of Example 1.

  The outline | summary of 1 aspect of this indication is as follows.

[Item 1]
Each is
A source region and a drain region formed in a semiconductor substrate;
A gate insulating layer on a semiconductor substrate;
A transparent gate electrode on the gate insulating layer;
Having a plurality of detection cells,
The gate insulating layer has a photoelectric conversion layer including a first photoelectric conversion material and a second photoelectric conversion material having absorption peaks different from each other,
Each of the plurality of detection cells outputs, from one of the source region and the drain region, an electric signal corresponding to a change in the dielectric constant of the photoelectric conversion layer, which is caused by light incident on the photoelectric conversion layer through the transparent gate electrode. A photodetection device.

  According to the structure of the item 1, compared with the case where a single photoelectric conversion material is used, the wavelength range which can be detected can be expanded using the change of the dielectric constant in a photoelectric converting layer.

[Item 2]
Item 2. The photodetection device according to Item 1, wherein the gate insulating layer includes an insulating layer disposed between the photoelectric conversion layer and the semiconductor substrate.

  According to the configuration of item 2, it is possible to reduce the leakage current in the photoelectric conversion layer and ensure the necessary S / N ratio.

[Item 3]
Item 3. The photodetection device according to Item 1 or 2, further comprising a light-shielding film disposed between the transparent gate electrode and the semiconductor substrate.

  According to the configuration of item 3, it is possible to suppress the incidence of stray light to the channel region formed between the source region and the drain region, so that mixing of noise such as color mixture between adjacent detection cells is suppressed. Can do.

[Item 4]
A bandpass filter including a first filter and a second filter having different wavelength ranges to be transmitted;
The plurality of detection cells include a first detection cell and a second detection cell,
The first filter faces the transparent gate electrode of the first detection cell,
4. The photodetecting device according to any one of items 1 to 3, wherein the second filter faces the transparent gate electrode of the second detection cell.

  According to the configuration of item 4, light in a desired wavelength range can be selectively incident on the photoelectric conversion layer of the desired detection cell among the plurality of detection cells. While having a common configuration, light in different wavelength ranges can be detected for each detection cell.

[Item 5]
Item 5. The photodetector according to item 4, wherein each of the transparent gate electrode of the first detection cell and the transparent gate electrode of the second detection cell is a part of a single continuous electrode.

  According to the configuration of item 5, the manufacturing process can be prevented from becoming complicated.

[Item 6]
The photoelectric conversion layer includes a first voltage range in which the absolute value of the output current density increases as the reverse bias voltage increases, a second voltage range in which the output current density increases as the forward bias voltage increases, and a first voltage range And a third voltage range between the first voltage range and the second voltage range, the change rate of the output current density with respect to the bias voltage has different photocurrent characteristics,
6. The photodetector according to any one of items 1 to 5, wherein a change rate in the third voltage range is smaller than a change rate in the first voltage range and a change rate in the second voltage range.

  According to the configuration of item 6, it is possible to provide a photodetection device that responds quickly to changes in illuminance. For example, it is possible to provide an infrared detection device that responds quickly to changes in illuminance.

[Item 7]
A voltage supply circuit for supplying a gate voltage within the third voltage range to the transparent gate electrode when the other potential of the source region and the drain region is used as a reference;
Each of the plurality of detection cells responds to a change in the dielectric constant of the photoelectric conversion layer while the potential difference between the other of the source region and the drain region and the transparent gate electrode is maintained within the third voltage range. Item 7. The photodetector according to item 6, wherein the electrical signal is output from one of the source region and the drain region.

  According to the configuration of item 7, it is possible to give a potential difference in the third voltage range between the source region or the drain region and the transparent gate electrode.

[Item 8]
Each is
A first electrode;
A field effect transistor formed in a semiconductor substrate, the gate of which is electrically connected to the first electrode;
A translucent second electrode facing the first electrode;
A photoelectric conversion layer disposed between the first electrode and the second electrode;
Having a plurality of detection cells,
The photoelectric conversion layer includes a first photoelectric conversion material and a second photoelectric conversion material having absorption peaks different from each other,
The photoelectric conversion layer includes a first voltage range in which the absolute value of the output current density increases as the reverse bias voltage increases, a second voltage range in which the output current density increases as the forward bias voltage increases, and a first voltage range And a third voltage range between the first voltage range and the second voltage range, the change rate of the output current density with respect to the bias voltage has different photocurrent characteristics,
The rate of change in the third voltage range is smaller than the rate of change in the first voltage range and the rate of change in the second voltage range,
Each of the plurality of detection cells is in a state where the potential difference between one of the source and drain of the field effect transistor and the second electrode is maintained in the first voltage range or the third voltage range. An optical detection device that outputs an electrical signal corresponding to a change in dielectric constant between the first electrode and the second electrode, which is generated by the incidence of light to the photoelectric conversion layer via the electrode, from the other of the source and the drain .

  According to the configuration of item 8, as compared with the case where a single photoelectric conversion material is used, the wavelength range that can be detected is expanded using the change in the dielectric constant between the first electrode and the second electrode. obtain.

[Item 9]
Item 9. The photodetector according to Item 8, further comprising at least one insulating layer disposed between the first electrode and the photoelectric conversion layer and at least one between the photoelectric conversion layer and the second electrode.

  According to the configuration of item 9, a larger bias voltage can be applied between the source or drain of the field effect transistor and the second electrode.

[Item 10]
Item 10. The photodetection device according to Item 9, further comprising a voltage supply circuit that supplies a voltage within the first voltage range to the second electrode when the potential of one of the source and the drain is used as a reference.

  According to the configuration of item 10, it is possible to provide a potential difference in the first voltage range between the source or drain of the field effect transistor and the second electrode.

[Item 11]
Item 10. The photodetecting device according to Item 8 or 9, further comprising a voltage supply circuit that supplies a voltage within the third voltage range to the second electrode when the potential of one of the source and the drain is used as a reference.

  According to the configuration of item 11, it is possible to give a potential difference in the third voltage range between the source or drain of the field effect transistor and the second electrode.

[Item 12]
Item 12. The photodetecting device according to any one of Items 8 to 11, wherein the first electrode is a light-shielding electrode.

  According to the configuration of item 12, since it is possible to suppress the incidence of stray light to the channel region of the field effect transistor, it is possible to suppress the mixing of noise such as a color mixture between adjacent detection cells.

[Item 13]
The gate of the field effect transistor includes a gate insulating layer and a gate electrode provided on the semiconductor substrate,
13. The photodetecting device according to any one of items 8 to 12, wherein the first electrode has a connection portion that connects the gate electrode and the first electrode.

  According to the structure of item 13, the freedom degree of design of the wiring arrange | positioned between a semiconductor substrate and a 1st electrode improves.

[Item 14]
A bandpass filter including a first filter and a second filter having different wavelength ranges to be transmitted;
The plurality of detection cells include a first detection cell and a second detection cell,
The first filter faces the second electrode of the first detection cell,
14. The photodetecting device according to any one of items 8 to 13, wherein the second filter faces the second electrode of the second detection cell.

  According to the configuration of item 14, light in a desired wavelength range can be selectively incident on the photoelectric conversion layer of a desired detection cell among the plurality of detection cells. While having a common configuration, light in different wavelength ranges can be detected for each detection cell.

[Item 15]
Item 15. The photodetector according to item 14, wherein each of the second electrode of the first detection cell and the second electrode of the second detection cell is a part of a single continuous electrode.

  According to the configuration of item 15, the manufacturing process can be prevented from becoming complicated.

[Item 16]
Item 16. The photodetector according to item 14 or 15, wherein each of the photoelectric conversion layer of the first detection cell and the photoelectric conversion layer of the second detection cell is a part of a single continuous layer.

  According to the configuration of item 16, it is possible to avoid complication of the manufacturing process.

[Item 17]
The first filter selectively transmits light in the first wavelength range of visible light, and the second filter selectively transmits light in the second wavelength range of visible light. , 14, 15 or 16.

  According to the configuration of item 17, for example, an RGB color image sensor can be realized.

[Item 18]
The first filter selectively transmits light in the first wavelength range out of visible light, and the second filter selectively transmits infrared light in the second wavelength range, Item 4, 5, 14, 15 or The photodetection device according to any one of 16.

  According to the structure of the item 18, the photodetector which can acquire the information regarding the illumination intensity of visible light and the illumination intensity of infrared rays can be provided.

[Item 19]
Item 19. The photodetection device according to Item 17 or 18, wherein the absorption peak of the first photoelectric conversion material is in the first wavelength range.

[Item 20]
Item 20. The photodetecting device according to any one of Items 17 to 19, wherein the absorption peak of the second photoelectric conversion material is in the second wavelength range.

[Item 21]
21. The photodetector according to any one of items 1 to 20, wherein the photoelectric conversion layer has a laminated structure of a first photoelectric conversion material and a second photoelectric conversion material.

  According to the configuration of the item 21, the adjustment of the thickness ratio between the first photoelectric conversion material layer and the second photoelectric conversion material layer is relatively easy. It is possible to control the degree of modulation of the dielectric constant caused by the incidence of light between the wavelength ranges.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. The various aspects described herein can be combined with each other as long as no contradiction arises. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements. In the following description, components having substantially the same function are denoted by common reference numerals, and description thereof may be omitted.

(First Embodiment of Photodetector)
FIG. 1 schematically illustrates a cross-section of an exemplary photodetection device according to the first embodiment of the present disclosure. The light detection apparatus 1000 shown in FIG. 1 includes two or more detection cells 10A each having a light detection structure 100A. For example, the detection cells 10A are arranged in a matrix to form an optical sensor array. Note that FIG. 1 schematically illustrates the arrangement of each unit included in the light detection apparatus 1000, and the size of each unit illustrated in FIG. 1 does not strictly reflect the size of an actual device. The same applies to other drawings of the present disclosure.

  FIG. 1 schematically shows a cross section of three detection cells 10Aa to 10Ac arranged in the row direction of the photosensor array among the plurality of detection cells 10A. The shapes and sizes of the detection cells 10Aa to 10Ac when viewed from the normal direction of the semiconductor substrate 20 may be the same between them, or may be different in some or all of them. Typically, the optical sensor array has a repeating structure with one or more detection cells 10A (for example, a set of detection cells 10Aa to 10Ac) as a unit. Needless to say, the arrangement of the detection cells 10Aa to 10Ac illustrated in FIG. 1 is merely an example, and it is not essential that these are arranged in a straight line.

  The plurality of detection cells 10 </ b> A are formed on the semiconductor substrate 20. Here, a p-type silicon (Si) substrate is illustrated as the semiconductor substrate 20. Each of the detection cells 10 </ b> A is electrically isolated from each other by an element isolation region 20 t formed in the semiconductor substrate 20. A distance between two adjacent detection cells 10A (which may be referred to as a pixel pitch) may be about 2 μm, for example. Note that the “semiconductor substrate” in this specification is not limited to a substrate that is entirely a semiconductor, and may be an insulating substrate in which a semiconductor layer is provided on the surface irradiated with light.

  The light detection structure 100A in the detection cell 10A generally has a device structure similar to a field effect transistor (FET). That is, the light detection structure 100A includes impurity regions (in this case, n-type regions) 20s and 20d formed in the semiconductor substrate 20, a gate insulating layer 23 disposed on the semiconductor substrate 20, and a gate insulating layer 23. The transparent gate electrode 22g is disposed. As shown in FIG. 1, the transparent gate electrode 22 g is disposed on the interlayer insulating layer 50 that covers the semiconductor substrate 20. In the example shown in FIG. 1, the transparent gate electrode 22g on the interlayer insulating layer 50 is formed over the plurality of detection cells 10A. That is, here, each of the transparent gate electrode 22g in the detection cell 10Aa, the transparent gate electrode 22g in the detection cell 10Ab, and the transparent gate electrode 22g in the detection cell 10Ac is a part of a single continuous electrode. By forming the transparent gate electrode 22g in the form of a single continuous electrode between the plurality of detection cells 10A, the manufacturing process can be prevented from becoming complicated.

  In the configuration illustrated in FIG. 1, the gate insulating layer 23 penetrates the interlayer insulating layer 50 and connects the upper surface of the semiconductor substrate 20 and the lower surface of the transparent gate electrode 22g. Note that the terms “upper surface” and “lower surface” in the present specification are used to indicate a relative arrangement between members, and are not intended to limit the posture of the light detection device of the present disclosure.

  The gate insulating layer 23 includes a photoelectric conversion layer 23p. As will be described in detail later, each detection cell 10A generates an electrical signal corresponding to a change in the dielectric constant of the photoelectric conversion layer 23p caused by the incidence of light on the photoelectric conversion layer 23p via the transparent gate electrode 22g. 20 is output from the impurity region (in this case, the impurity region 20s) formed in the semiconductor layer 20.

  The photoelectric conversion layer 23p includes first and second photoelectric conversion materials having absorption peaks different from each other. By forming the photoelectric conversion layer 23p using the first and second photoelectric conversion materials, it is possible to expand the detectable wavelength range compared to the case of using a single photoelectric conversion material. . Therefore, the light detection structure 100A having sensitivity in a plurality of wavelength ranges can be realized. For example, the light detection structure 100A having sensitivity in both the wavelength range of visible light (for example, 380 nm or more and 780 nm or less) and the infrared wavelength range can be realized. Details of the configuration of the photoelectric conversion layer 23p, and examples of the first photoelectric conversion material and the second photoelectric conversion material will be described later. The thickness of the photoelectric conversion layer 23p (the length measured along the normal direction of the semiconductor substrate 20) is, for example, about 1500 nm.

In the configuration illustrated in FIG. 1, the insulating layer 23 x is disposed between the photoelectric conversion layer 23 p and the semiconductor substrate 20. By disposing the insulating layer 23x between the photoelectric conversion layer 23p and the semiconductor substrate 20, a leakage current in the photoelectric conversion layer 23p can be reduced and a necessary S / N ratio can be ensured. As the insulating layer 23x, for example, a silicon thermal oxide film or an aluminum oxide film can be used. As the insulating layer 23x, a silicon oxynitride film (SiON film) generally used in a silicon semiconductor may be applied, or a High-k film such as an HfO ₂ film may be applied. The thickness of the insulating layer 23x may be set as appropriate according to the material constituting the insulating layer 23x.

  In the example shown in FIG. 1, a band-pass filter 26 is disposed on the transparent gate electrode 22g. The band filter 26 includes a plurality of portions having different wavelength ranges for transmission. In the configuration illustrated in FIG. 1, the band-pass filter 26 includes a first filter 26a facing the transparent gate electrode 22g in the detection cell 10Aa, a second filter 26b facing the transparent gate electrode 22g in the detection cell 10Ab, and the detection cell 10Ac. Has a third filter 26c facing the transparent gate electrode 22g. A black matrix may be disposed between two adjacent filters among the first filter 26a, the second filter 26b, and the third filter 26c (not shown in FIG. 1).

  For example, the first filter 26a, the second filter 26b, and the third filter 26c may be color filters that selectively transmit light in the red (R), green (G), and blue (B) wavelength ranges, respectively. By disposing portions (first filter 26a, second filter 26b, and third filter 26c) having different transmission spectra in the band filter 26 corresponding to the plurality of detection cells 10A, a desired one of the plurality of detection cells 10A. The light of a desired wavelength range can be selectively incident on the photoelectric conversion layer 23p of the detection cell 10A. In other words, it is possible to detect light in different wavelength ranges for each detection cell 10A while making the configuration of the photoelectric conversion layer 23p common among the plurality of detection cells 10A. It can be used as a sensor. Of course, the wavelength range of light that is selectively transmitted by the filter included in the band filter 26 is not limited to the wavelength range of red (R), green (G), or blue (B), but in the wavelength range of other colors. There may be.

  The filter included in the band filter 26 is not limited to a filter that transmits visible light. For example, at least one of the first filter 26a, the second filter 26b, and the third filter 26c selectively transmits infrared light. An IR filter may be used. Alternatively, the bandpass filter 26 transmits an R filter that transmits red light (wavelength: 620 to 750 nm), a G filter that transmits green light (wavelength: 490 to 585 nm), and a B filter that transmits blue light (wavelength: 400 to 495 nm). A filter and an IR filter that transmits infrared light may be included. By including the infrared transmission filter in the band filter 26, the detection cell 10A having the transparent gate electrode 22g facing the infrared transmission filter can function as an infrared detection cell. Therefore, for example, by using a bandpass filter including a filter that transmits visible light and a filter that transmits infrared light, the light detection apparatus 1000 can acquire information on the illuminance of visible light and the illuminance of infrared light. . That is, for example, the light detection apparatus 1000 can be used as a visible light detection apparatus and an infrared detection apparatus. Alternatively, the photodetection device 1000 can be used as a color area sensor and an infrared area sensor. If a filter that transmits visible light uses the output from the plurality of detection cells 10A arranged facing the transparent gate electrode 22g, a color image can be acquired, and a filter that transmits infrared light faces the transparent gate electrode 22g. Infrared images can be acquired by using outputs from a plurality of detection cells 10A arranged in the same manner.

  As described above, the light detected by the light detection apparatus 1000 is not limited to light within the wavelength range of visible light. In this specification, electromagnetic waves in general including infrared rays and ultraviolet rays are expressed as “light” for convenience. In this specification, the terms “transparent” and “translucent” mean transmitting at least part of light in the wavelength range to be detected, and transmitting light over the entire wavelength range of visible light Not required.

For example, when the band-pass filter 26 includes a filter that selectively transmits visible light and an infrared transmission filter, a material having a high transmittance for visible light and near infrared rays and a low resistance value is selected as the material of the transparent gate electrode 22g. It is. For example, a transparent conductive oxide (Transparent Oxide (TCO)) can be used as the material of the transparent gate electrode 22g. As TCO, for example, ITO, IZO, AZO, FTO, SnO ₂ , TiO ₂ , ZnO _{2 and the} like can be used. A metal thin film such as Au may be used as the transparent gate electrode 22g.

  The transparent gate electrode 22g has a connection with a power source (not shown). The transparent gate electrode 22g is configured to be able to apply a predetermined bias voltage (first bias voltage) during operation of the light detection device 1000. Here, since the transparent gate electrode 22g is formed over the plurality of detection cells 10A, the first bias voltage can be collectively applied to the plurality of detection cells 10A.

  In the configuration illustrated in FIG. 1, the interlayer insulating layer 50 has a stacked structure including a plurality of insulating layers (typically silicon oxide films). A multilayer wiring 40 is disposed in the interlayer insulating layer 50. The multilayer wiring 40 includes a plurality of wiring layers. In the configuration illustrated in FIG. 1, the multilayer wiring 40 includes three wiring layers, and a power supply wiring 42, an address signal line 44, and a vertical signal line 46 are provided in the central wiring layer. The power supply wiring 42, the address signal line 44, and the vertical signal line 46 extend, for example, along a direction perpendicular to the paper surface (column direction in the photosensor array). In the example illustrated in FIG. 1, the interlayer insulating layer 50 and the multilayer wiring 40 include four insulating layers and three wiring layers, respectively. However, the number of insulating layers in the interlayer insulating layer 50 and the number of wiring layers in the multilayer wiring 40 are not limited to this example.

  In the configuration illustrated in FIG. 1, the power supply wiring 42 of the multilayer wiring 40 is connected to the impurity region 20 d through the contact plug 52. As will be described later, the power supply wiring 42 is connected to a power supply for supplying a predetermined voltage. During the operation of the photodetection device 1000, a predetermined bias voltage (second bias voltage) is applied to the impurity region 20d through the power supply wiring 42, similarly to the transparent gate electrode 22g.

  During operation of the photodetection device 1000, a predetermined voltage is applied to the transparent gate electrode 22g and the impurity region 20d, whereby the potential difference between the transparent gate electrode 22g and the impurity region 20d is maintained constant. If the potential difference between the transparent gate electrode 22g and the impurity region 20d can be kept constant during operation, the transparent gate electrode 22g may not be formed over the plurality of detection cells 10A. For example, the transparent gate electrode 22g may be formed separately for each detection cell 10A.

  As will be described in detail later, in the light detection operation, with the potential difference between the transparent gate electrode 22g and the impurity region 20d maintained constant, the light detection structure 100A side of the light detection structure 100A (in FIG. 1) From the upper side), the light detection device 1000 is irradiated with light. The light irradiated to the photodetection device 1000 is incident on the photoelectric conversion layer 23p of the gate insulating layer 23 through the transparent gate electrode 22g. The photoelectric conversion layer 23p generates positive and negative charge pairs (for example, electron-hole pairs) when irradiated with light. The generation of a pair of positive and negative charges in the photoelectric conversion layer 23p changes the dielectric constant of the photoelectric conversion layer 23p. When the photodetection structure 100A is regarded as a field effect transistor, the dielectric constant in the photoelectric conversion layer 23p changes, so that the same effect as when the gate capacitance in this transistor changes is produced. That is, the threshold voltage of this transistor changes due to light irradiation to the gate insulating layer 23. By utilizing this change, it is possible to detect light.

  From such an operation principle, the light detection structure 100A may be called a capacitance modulation transistor. The impurity regions 20s and 20d correspond to, for example, a source region and a drain region of the capacitance modulation transistor, respectively. Hereinafter, the impurity region 20s may be referred to as a source region (or drain region), and the impurity region 20d may be referred to as a drain region (or source region). In the following, for the sake of simplicity, the current flowing between the impurity regions 20s and 20d may be simply referred to as a drain current.

  As described above, in a typical embodiment of the present disclosure, the photoelectric conversion layer 23p includes the first and second photoelectric conversion materials having different absorption peaks. Therefore, the change in the dielectric constant in the photoelectric conversion layer 23p can be caused not only by the incidence of light in a specific wavelength range but also by the incidence of light in other wavelength ranges. Therefore, according to the embodiment of the present disclosure, it is possible to detect, for example, light in two different wavelength ranges by a single detection cell by using the change in the dielectric constant in the photoelectric conversion layer 23p. In particular, as illustrated in FIG. 1, an optical filter (a color filter, an IR filter, or the like) that selectively transmits light in a specific wavelength range is disposed on the light incident side of the photoelectric conversion layer 23p, and the photoelectric conversion layer 23p By selecting the wavelength range of the incident light, the photoelectric conversion layer is made common among the plurality of detection cells, and the change of the dielectric constant in the photoelectric conversion layer 23p is utilized to change the wavelength range different for each detection cell. Light can be detected.

  In the configuration illustrated in FIG. 1, each detection cell 10 </ b> A includes an address transistor 30. Address transistor 30 includes impurity regions 20 s and 30 s formed in semiconductor substrate 20, gate insulating layer 33, and gate electrode 34. In the following, an N-channel MOSFET will be exemplified as a transistor unless otherwise specified.

  The gate insulating layer 33 and the gate electrode 34 are, for example, a silicon thermal oxide film (silicon dioxide film) and a polysilicon electrode, respectively. In this example, the address transistor 30 and the light detection structure 100A share the impurity region 20s, and these are electrically connected by sharing the impurity region 20s.

  The impurity regions 20s and 30s in the address transistor 30 function as, for example, a drain region and a source region of the address transistor 30, respectively. The gate electrode 34 (typically a polysilicon electrode) and the impurity region 30 s of the address transistor 30 are connected to the address signal line 44 and the vertical signal line 46 of the multilayer wiring 40 through the contact plug 52, respectively. Therefore, by controlling the potential of the gate electrode 34 via the address signal line 44 and turning on the address transistor 30, a signal generated by the light detection structure 100 A is selectively transmitted via the vertical signal line 46. Can be read.

  The above-described multilayer wiring 40 including the vertical signal line 46 and the like as a part thereof is formed of a metal such as copper. A light shielding film may be formed by a wiring layer in the multilayer wiring 40. By causing the wiring layer disposed in the interlayer insulating layer 50 to function as a light shielding film, light that has not entered the photoelectric conversion layer 23p out of the light transmitted through the transparent gate electrode 22g is blocked by the light shielding wiring layer. It is possible. Thereby, it is possible to suppress the light that has not entered the photoelectric conversion layer 23p from entering the channel region of the transistor (capacitance modulation transistor or address transistor 30) formed in the semiconductor substrate 20. The insulating layer 23x and / or the gate insulating layer 33 may have a light shielding property. By suppressing the incidence of stray light to the channel region, it is possible to suppress the mixing of noise such as a color mixture between adjacent detection cells. Of the light transmitted through the transparent gate electrode 22g, most of the light traveling toward the photoelectric conversion layer 23p is absorbed by the photoelectric conversion layer 23p. Therefore, the light traveling toward the photoelectric conversion layer 23p does not adversely affect the operation of the transistor formed on the semiconductor substrate 20.

  As shown in FIG. 1, a microlens 28 that collects irradiated light and makes it incident on the photoelectric conversion layer 23p may be disposed on the band filter 26 so as to correspond to each detection cell 10A. A protective layer may be disposed on the upper surface and / or the lower surface of the band-pass filter 26. In this example, a protective layer 25a and a protective layer 25b are disposed between the band filter 26 and the transparent gate electrode 22g of each detection cell 10A, and between the microlens 28 and the band filter 26, respectively.

(Exemplary circuit configuration of photodetection device)
FIG. 2 shows an exemplary circuit configuration of the photodetection device 1000. As described above, the light detection structure 100A has a device structure similar to a field effect transistor. Therefore, here, the photodetection structure 100A is expressed for convenience by using a circuit symbol similar to that of a transistor.

  FIG. 2 schematically shows an example in which the detection cells 10A are arranged in a matrix of 2 rows and 2 columns. In this specification, the direction in which a row and a column extend may be referred to as a row direction and a column direction, respectively. Needless to say, the number and arrangement of detection cells in the light detection apparatus 1000 are not limited to the example shown in FIG. The detection cells may be arranged in one dimension. In this case, the light detection apparatus 1000 is a line sensor. The number of detection cells included in the light detection apparatus 1000 is typically two or more.

  As already described, the impurity region 20d (which may be called the drain of the capacitance modulation transistor) in the light detection structure 100A of each detection cell 10A is connected to the power supply wiring 42. In the example shown in FIG. 2, the power supply wiring 42 is arranged for each column of the photosensor array. These power supply wirings 42 are connected to the voltage supply circuit 12. During operation of the photodetection device 1000, the voltage supply circuit 12 supplies a predetermined voltage (second bias voltage) to each of the detection cells 10A constituting the photosensor array via the power supply wiring.

  The transparent gate electrode 22g in the light detection structure 100A of each detection cell 10A is connected to the gate voltage control line 48. In the configuration illustrated in FIG. 2, the gate voltage control line 48 is connected to the voltage supply circuit 12. Therefore, during the operation of the photodetection device 1000, a predetermined gate voltage (first bias) is applied to the transparent gate electrode 22 g of each photodetection structure 100 A in the photosensor array from the voltage supply circuit 12 via the gate voltage control line 48. Voltage) is applied. The voltage supply circuit 12 is not limited to a specific power supply circuit, and may be a circuit that generates a predetermined voltage, or may be a circuit that converts a voltage supplied from another power supply into a predetermined voltage. . As will be described later, a gate voltage within a predetermined range is applied to the transparent gate electrode 22g of each light detection structure 100A with reference to the potential of the impurity region 20d in the light detection structure 100A.

  In the configuration illustrated in FIG. 2, the address signal line 44 having a connection with the gate of the address transistor 30 is connected to a vertical scanning circuit (also referred to as “row scanning circuit”) 14. The vertical scanning circuit 14 selects a plurality of detection cells 10 </ b> A arranged in each row by applying a predetermined voltage to the address signal line 44. Thereby, the signal of the selected detection cell 10 </ b> A can be read out via the address transistor 30.

  As shown in the figure, one of the source and drain (typically drain) of the address transistor 30 is connected to the impurity region 20s (which may be called the source of the capacitance modulation transistor) in the light detection structure 100A, and the address transistor 30 The other of the source and the drain of the transistor 30 (here, the source) is connected to a vertical signal line 46 provided for each column of the photosensor array. The vertical signal line 46 is a main signal line that transmits a pixel signal from the photosensor array to a peripheral circuit.

  In this example, a constant current source 49 is connected between the vertical signal line 46 and the ground. Therefore, by detecting a change in the voltage of the vertical signal line 46, it is possible to detect a change in the threshold voltage in the light detection structure 100A due to the light being irradiated to the light detection structure 100A. That is, light can be detected based on a change in the voltage of the vertical signal line 46. At this time, the power supply wiring 42 functions as a source follower power supply. Light may be detected by detecting a current output from the impurity region 20s of the light detection structure 100A. However, it is more advantageous to detect a change in voltage from the viewpoint of obtaining a high S / N ratio because a process and a circuit similar to those of an optical sensor using a silicon photodiode can be applied.

  The circuit for supplying a predetermined voltage to the impurity region 20d in the light detection structure 100A and the circuit for supplying a predetermined voltage to the transparent gate electrode 22g may be common as illustrated in FIG. May be different. At least one of a circuit for supplying a predetermined voltage to the impurity region 20d and a circuit for supplying a predetermined voltage to the transparent gate electrode 22g in the light detection structure 100A may be a part of the vertical scanning circuit 14.

(Photoelectric conversion layer)
Next, a typical example of the configuration of the photoelectric conversion layer 23p will be described in detail.

  As a material constituting the photoelectric conversion layer 23p, a semiconductor material is typically used. The photoelectric conversion layer 23p generates positive and negative charge pairs (typically, electron-hole pairs) in response to light irradiation. Here, an organic semiconductor material is used as a material constituting the photoelectric conversion layer 23p. In this case, the photoelectric conversion layer 23p typically includes an organic p-type semiconductor (compound) and an organic n-type semiconductor (compound).

  The organic p-type semiconductor (compound) is a donor-type organic semiconductor (compound), which is mainly represented by a hole-transporting organic compound and refers to an organic compound having a property of easily donating electrons. More specifically, an organic p-type semiconductor (compound) refers to an organic compound having a smaller ionization potential when two organic materials are used in contact with each other. Therefore, any organic compound can be used as the donor organic compound as long as it is an electron-donating organic compound. For example, triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds such as P3HT, phthalocyanine compounds such as subphthalocyanine (SubPc) or copper phthalocyanine, Naphthalocyanine compounds such as tin naphthalocyanine, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracenes) Derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), nitrogen-containing heterocyclic compounds Or the like can be used a metal complex having as a child. The donor organic semiconductor is not limited to these, and any organic compound having an ionization potential smaller than that of the organic compound used as the n-type (acceptor) compound can be used as the donor organic semiconductor.

Organic n-type semiconductors (compounds) are acceptor organic semiconductors (compounds), which are mainly represented by electron-transporting organic compounds and refer to organic compounds that easily accept electrons. More specifically, an organic n-type semiconductor (compound) refers to an organic compound having a higher electron affinity when two organic compounds are used in contact with each other. Therefore, as the acceptor organic compound, any organic compound can be used as long as it is an electron-accepting organic compound. For example, fullerenes such as C _60, fullerene derivatives such as phenyl C ₆₁ butyric acid methyl ester (PCBM), a fused aromatic carbocyclic compound (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives) A 5- to 7-membered heterocyclic compound containing a nitrogen atom, oxygen atom, sulfur atom (for example, pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, Phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole Carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compound, fluorene compound, cyclopentadiene A compound, a silyl compound, a perylene tetracarboxyl diimide compound (PTCDI), a metal complex having a nitrogen-containing heterocyclic compound as a ligand, or the like can be used. In addition, not only these but an organic compound with an electron affinity larger than the organic compound used as a p-type (donor property) organic compound can be used as an acceptor organic semiconductor.

In the embodiment of the present disclosure, the above-described organic p-type semiconductor (compound) and organic n-type semiconductor (compound) can be used as the first and second photoelectric conversion materials, respectively. For example, a combination of tin naphthalocyanine and C ₆₀ can be applied as a combination of the first photoelectric conversion material and the second photoelectric conversion material.

Tin naphthalocyanine is represented by the following general formula (1).

In general formula (1), R < ¹ > -R < ²⁴ > represents a hydrogen atom or a substituent independently. The substituent is not limited to a specific substituent. Substituents include deuterium atoms, halogen atoms, alkyl groups (including cycloalkyl groups, bicycloalkyl groups, and tricycloalkyl groups), alkenyl groups (including cycloalkenyl groups and bicycloalkenyl groups), alkynyl groups, aryl groups, Heterocyclic group (may be referred to as heterocyclic group), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyl Oxy group, aryloxycarbonyloxy group, amino group (including anilino group), ammonio group, acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkylsulfonylamino group The ant Rusulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, sulfo group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxy Carbonyl group, carbamoyl group, arylazo group, heterocyclic azo group, imide group, phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, phosphono group, silyl group, hydrazino group, ureido group, boronic acid group (-B (OH) _2), phosphato group (-OPO (OH) _2), a sulfato group (-OSO ₃ H), or may be other known substituents.

As the tin naphthalocyanine represented by the above general formula (1), a commercially available product can be used. Alternatively, tin naphthalocyanine represented by the above general formula (1) is obtained by using a naphthalene derivative represented by the following general formula (2) as a starting material, as disclosed in, for example, JP-A-2010-232410. Can be synthesized. R ^{25 to} R ³⁰ in the general formula (2) may be the same substituents as R ^{1 to} R ²⁴ in the general formula (1).

In the tin naphthalocyanine represented by the general formula (1), eight or more of R ^{1 to} R ²⁴ are hydrogen atoms or deuterium atoms from the viewpoint of easy control of the molecular aggregation state. It is beneficial that 16 or more of R ^{1 to} R ²⁴ are hydrogen atoms or deuterium atoms, and it is further beneficial that all are hydrogen atoms or deuterium atoms. Furthermore, tin naphthalocyanine represented by the following formula (3) is advantageous from the viewpoint of ease of synthesis.

  Tin naphthalocyanine represented by the above general formula (1) has absorption in a wavelength band of approximately 200 nm to 1100 nm. For example, tin naphthalocyanine represented by the above formula (3) may have an absorption peak at a wavelength of about 870 nm. That is, tin naphthalocyanine has absorption in the near-infrared region, and by selecting tin naphthalocyanine as the first photoelectric conversion material, the light detection structure 100A capable of detecting near-infrared light can be realized.

On the other hand, C ₆₀ has an absorption peak at a position where the wavelength is approximately 440 nm. That is, it can be said that the absorption peak at C ₆₀ is located within the wavelength range of blue light. C ₆₀ also exhibits absorption even when the wavelength is around 700 nm. In other words, C ₆₀ also absorbs red light. Accordingly, the second photoelectric conversion material, by selecting the C _60, can realize detectable light sensing structure 100A visible light (especially blue light). FIG. 3 shows an absorption spectrum of C ₆₀ obtained by transmission measurement. In the measurement, a spectrophotometer U4100 manufactured by Hitachi High-Technology Co., Ltd. is used, and a sample in which a C ₆₀ layer is formed on a quartz substrate by vacuum deposition (C ₆₀ layer thickness: 50 nm) is used. In forming the C ₆₀ layer, C ₆₀ is deposited at a film formation rate of 1 kg / sec under a high vacuum of 5.0 × 10 ⁻⁴ Pa or less (“×” represents multiplication).

  FIG. 4 schematically shows the gate insulating layer 23 and its periphery in the light detection structure 100A. As illustrated in FIG. 4, the photoelectric conversion layer 23 p includes a first layer 122 p mainly including a first photoelectric conversion material (here, an organic p-type semiconductor material) and a second photoelectric conversion material (here, an organic n-type semiconductor). 120s including the second layer 122n including a material. The first layer 122p has a function of photoelectric conversion and / or hole transport. The second layer 122n has a function of photoelectric conversion and / or electron transport. In this example, an electron blocking layer 120e and a hole blocking layer 120h are disposed between the insulating layer 23x and the first layer 122p and between the transparent gate electrode 22g and the second layer 122n, respectively. Yes. Thus, the photoelectric conversion layer 23p may include the electron blocking layer 120e and / or the hole blocking layer 120h.

  According to the stacked structure of the first layer 122p and the second layer 122n, the thickness ratio between the first layer 122p and the second layer 122n can be adjusted relatively easily. By adjusting the ratio of these thicknesses, the degree of modulation of the dielectric constant in the photoelectric conversion layer 23p when the light in the wavelength range in which the first photoelectric conversion material exhibits absorption and the second photoelectric conversion material exhibit absorption. It is possible to control the degree of dielectric constant modulation in the photoelectric conversion layer 23p when light in the wavelength region is incident.

  FIG. 5 shows another example of the configuration of the photoelectric conversion layer 23p. In the configuration illustrated in FIG. 5, the photoelectric conversion layer 23p includes a photoelectric conversion structure 120t sandwiched between an electron blocking layer 120e and a hole blocking layer 120h. The photoelectric conversion structure 120t includes a first layer 122p, a second layer 122n, and a mixed layer 122m. The mixed layer 122m is located between the first layer 122p and the second layer 122n.

  The mixed layer 122m can be, for example, a bulk heterojunction structure layer including a first photoelectric conversion material (here, p-type semiconductor material) and a second photoelectric conversion material (here, n-type semiconductor material). When the mixed layer 122m is formed as a layer having a bulk heterojunction structure, tin naphthalocyanine represented by the above general formula (1) can be used as a p-type semiconductor material. As the n-type semiconductor material, for example, fullerene and / or fullerene derivatives can be used. It is beneficial if the p-type semiconductor material contained in the first layer 122p is the same as the p-type semiconductor material contained in the mixed layer 122m. Similarly, it is beneficial if the n-type semiconductor material contained in the second layer 122n is the same as the n-type semiconductor material contained in the mixed layer 122m. The bulk heterojunction structure is described in detail in Japanese Patent No. 5553727. For reference, the entire disclosure of Japanese Patent No. 5553727 is incorporated herein by reference.

Figure 6 shows an example of absorption spectra for the bulk heterojunction structure of Suzuna phthalocyanine and C _60. In the measurement of the absorption spectrum, and using a sample with a spectrophotometer U4100 manufactured by the measurement as well as by Hitachi High-Technologies Corporation absorption spectra of C _60, deposited Suzuna phthalocyanine and C ₆₀ on a quartz substrate. The sample was prepared by performing co-evaporation under a high vacuum of 5.0 × 10 ⁻⁴ Pa or less at a film formation rate of 1 kg / sec, and the volume ratio of tin naphthalocyanine and C ₆₀ in the bulk heterojunction structure layer and Adjustments are made so that the thicknesses are 1: 1 and 50 nm, respectively.

As can be seen from FIG. 6, the absorption characteristics as a whole of the layer containing tin naphthalocyanine and C ₆₀ is an absorption obtained by superimposing the absorption characteristics of tin naphthalocyanine and the absorption characteristics of C ₆₀ (see FIG. 3). It becomes a characteristic. That is, the Suzuna phthalocyanine as a first photoelectric conversion material, to form a photoelectric conversion layer 23p as a layer having a structure containing a C ₆₀ as a second photoelectric conversion material, its photoelectric conversion layer 23p, the wavelength of near-infrared Shows relatively high absorption in the range and wavelength range of blue light. In other words, by using a structure comprising Suzuna phthalocyanine and C ₆₀ as a photoelectric conversion layer 23p, capable of realizing light detection structure 100A having sensitivity to infrared and visible light (especially blue light). For example, infrared light can be selectively detected if light transmitted through an infrared transmission filter, for example, is incident on the light detection structure 100A having the photoelectric conversion layer 23p. Similarly, for example, if light transmitted through a blue color filter is incident, it is possible to selectively detect blue light.

Instead of tin naphthalocyanine, for example, subphthalocyanine may be used as the first photoelectric conversion material. Subphthalocyanine is represented by the following general formula (4). As the subphthalocyanine represented by the following general formula (4), a commercially available product can be used. As the subphthalocyanine represented by the following general formula (4), for example, boron subphthalocyanine chloride provided by Sigma-Aldrich Japan LLC can be used. In this case, X in the following general formula (4) is chlorine.

FIG. 7 shows the absorption spectrum of subphthalocyanine represented by the above general formula (4), obtained by transmission measurement. In the measurement, a sample in which a subphthalocyanine layer (thickness: 50 nm) is formed on a quartz substrate using a spectrophotometer U4100 manufactured by Hitachi High-Technology, as in the example described with reference to FIGS. Is used. The film forming method and conditions in the preparation of the sample are the same as those in the above-described sample in which _C60 is deposited on a quartz substrate. In FIG. 7, the absorption spectrum related to C ₆₀ described with reference to FIG. 3 is also shown by a broken line.

As can be seen from FIG. 7, subphthalocyanine (SubPc) has an absorption peak at a wavelength of about 580 nm. That is, it can be said that the absorption peak in subphthalocyanine is located within the wavelength range of green light. As schematically shown in FIG. 8, the layer containing subphthalocyanine and C ₆₀ exhibits absorption characteristics obtained by superimposing these absorption characteristics. As described with reference to FIG. 3, C ₆₀ has an absorption peak in the vicinity of a wavelength of 440 nm and exhibits absorption in a wavelength range up to about 700 nm. Therefore, for example, by applying a structure (see FIG. 4 or 5) including subphthalocyanine as the first photoelectric conversion material and C ₆₀ as the second photoelectric conversion material, almost the entire wavelength range of visible light is applied. A photoelectric conversion layer 23p that absorbs over the whole can be formed.

  For example, red light can be selectively detected by making light transmitted through, for example, a red color filter incident on the light detection structure 100A having the photoelectric conversion layer 23p. Similarly, if light transmitted through the green color filter is incident, green light can be selectively detected, and if light transmitted through the blue color filter is incident, blue light can be selectively detected.

  As described above, an optical sensor having sensitivity in a desired wavelength range can be realized by using an appropriate material according to the wavelength range to be detected. By using a photoelectric conversion layer including a plurality of photoelectric conversion materials having different absorption peaks, it is possible to expand or increase the wavelength range exhibiting strong absorption compared to the case of using a single photoelectric conversion material. . In particular, a filter that selectively transmits light in a first wavelength range including a wavelength corresponding to one absorption peak is arranged opposite to a certain detection cell, and a wavelength corresponding to one other absorption peak is set. It may be beneficial to place a filter that selectively transmits light in the second wavelength range, including, opposite to some other detection cell. According to such a configuration, it is possible to selectively detect light in the first wavelength range and selectively detect light in the second wavelength range by the former while using a common photoelectric conversion layer. . Therefore, it is possible to relatively easily realize a photodetecting device having a photosensor array in which a first detection cell that detects infrared rays and a second detection cell that detects visible light are mixed. According to such a light detection device, for example, an infrared image can be acquired based on the output of the first detection cell, and a monochrome image related to the visible range can be acquired based on the output of the second detection cell. It is.

The formation method of the first layer 122p and the second layer 122n is not limited to a specific formation method, and for example, a dry deposition method such as vapor deposition or a wet deposition method such as coating can be applied. Similarly, the formation method of the mixed layer 122m is not limited to a specific formation method. Bulk heterojunction structure Suzuna phthalocyanine and C _60, for example, can be obtained by co-evaporation of Suzuna phthalocyanine and C _60. The specific structure of the photoelectric conversion layer 23p is not limited to the structure described with reference to FIGS. The photoelectric conversion layer 23p may have a configuration in which two or more types of photoelectric conversion materials are mixed, or has a laminated structure of two or more types of photoelectric conversion layers formed from different photoelectric conversion materials. May be. The photoelectric conversion layer 23p may include an inorganic semiconductor material such as amorphous silicon. The photoelectric conversion layer 23p may include a layer made of an organic material and a layer made of an inorganic material.

(Typical example of photocurrent characteristics in photoelectric conversion layer)
FIG. 9 shows a typical example of the photocurrent characteristic in the photoelectric conversion layer 23p. In FIG. 9, a thick solid line graph shows an exemplary IV characteristic of the photoelectric conversion layer in a state where light is irradiated. In FIG. 9, an example of the IV characteristic in a state where no light is irradiated is also shown by a thick broken line.

  FIG. 9 shows a change in current density between the main surfaces when the bias voltage applied between the two main surfaces of the photoelectric conversion layer is changed under a constant illuminance. In this specification, when a bias is applied between two main surfaces of the photoelectric conversion layer, the forward direction and the reverse direction in the bias voltage are defined as follows. When the photoelectric conversion layer has a layered p-type semiconductor and a layered n-type semiconductor junction structure, a bias voltage is set so that the potential of the p-type semiconductor layer is higher than that of the n-type semiconductor layer. Defined as bias voltage. On the other hand, a bias voltage in which the potential of the p-type semiconductor layer is lower than that of the n-type semiconductor layer is defined as a reverse bias voltage. When the organic semiconductor material is used, the forward direction and the reverse direction can be defined as in the case where the inorganic semiconductor material is used. When the photoelectric conversion layer has a bulk heterojunction structure, as schematically shown in FIG. 1 of the above-mentioned Japanese Patent No. 5553727, one of the two main surfaces of the photoelectric conversion layer has an n-type semiconductor. More p-type semiconductors appear, and more n-type semiconductors appear on the other surface than p-type semiconductors. Therefore, a bias voltage is applied in the forward direction such that the potential on the main surface side where more p-type semiconductors appear than the n-type semiconductor is higher than the potential on the main surface side where more n-type semiconductors appear than the p-type semiconductor. Defined as bias voltage.

  As shown in FIG. 9, the photocurrent characteristic of the photoelectric conversion layer according to the embodiment of the present disclosure is generally characterized by the first to third voltage ranges. The first voltage range is a reverse bias voltage range in which the absolute value of the output current density increases as the reverse bias voltage increases. The first voltage range may be a voltage range in which the photocurrent increases as the bias voltage applied between the main surfaces of the photoelectric conversion layer increases. The second voltage range is a forward bias voltage range in which the output current density increases as the forward bias voltage increases. That is, the second voltage range is a voltage range in which the forward current increases as the bias voltage applied between the main surfaces of the photoelectric conversion layer increases. The third voltage range is a voltage range between the first voltage range and the second voltage range.

  The first to third voltage ranges can be distinguished by the slope of the graph of the photocurrent characteristic when the linear vertical axis and horizontal axis are used. For reference, in FIG. 9, the average slope of the graph in each of the first voltage range and the second voltage range is indicated by a broken line L1 and a broken line L2, respectively. As illustrated in FIG. 9, the change rate of the output current density with respect to the increase of the bias voltage in the first voltage range, the second voltage range, and the third voltage range is different from each other. The third voltage range is defined as a voltage range in which the change rate of the output current density with respect to the bias voltage is smaller than the change rate in the first voltage range and the change rate in the second voltage range. Alternatively, the third voltage range may be determined based on the rising (falling) position in the graph indicating the IV characteristics. In the third voltage range, even if the bias voltage is changed, the current density between the main surfaces of the photoelectric conversion layer hardly changes. As will be described in detail later, in this third voltage range, positive and negative charge pairs (typically hole-electron pairs) generated by light irradiation rapidly recombine when light irradiation is stopped. Disappear. Therefore, a high-speed response can be realized by adjusting the bias voltage applied between the two main surfaces of the photoelectric conversion layer to the voltage in the third voltage range during the operation of the photodetector.

  Please refer to FIG. 1 and FIG. 2 again. In a typical embodiment of the present disclosure, during operation of the photodetection device, a potential difference between the side connected to the power supply wiring 42 of the two impurity regions formed in the semiconductor substrate 20 and the transparent gate electrode 22g The light detection is performed in a state where the third voltage range is maintained. For example, in the configuration described with reference to FIG. 2, the gate voltage within the third voltage range when the impurity region 20 d is used as a reference is supplied from the voltage supply circuit 12 to the transparent gate electrode 22 g.

When light enters the photoelectric conversion layer 23p, for example, hole-electron pairs are generated inside the photoelectric conversion layer 23p. At this time, since a predetermined bias voltage is applied to the photoelectric conversion layer 23p, the dipole moments in each of the plurality of hole-electron pairs are aligned in substantially the same direction. Therefore, the dielectric constant of the photoelectric conversion layer 23p increases with the generation of hole-electron pairs. When the magnitude of the electric field in the photoelectric conversion layer 23p in a state where a predetermined bias voltage is applied and irradiated with light is E, E = ((σ _f −σ _p ) / ε ₀ according to Gauss's law. ) And E = (σ _f / ε). Here, σ _f is the charge density in the electrode (for example, the transparent gate electrode 22g), and σ _p is the density of the charge generated on the surface facing the electrode in the photoelectric conversion layer 23p due to polarization. ε ₀ and ε are the dielectric constant of vacuum and the dielectric constant of the photoelectric conversion layer 23p, respectively. From E = ((σ _f −σ _p ) / ε ₀ ) and E = (σ _f / ε), ε = ε ₀ (σ _f / (σ _f −σ _p )) is obtained, and the charge contributing to polarization It can be seen that the increase in (hole-electron pairs) increases the dielectric constant of the photoelectric conversion layer 23p. That is, the dielectric constant of the entire gate insulating layer 23 is increased by irradiating the photoelectric conversion layer 23p with light.

  If the light detection structure 100A is regarded as a transistor, the threshold voltage decreases as the dielectric constant of the gate insulating layer 23 increases (it may be said that the effective gate voltage increases). As a result, the voltage of the impurity region 20 s changes with the change in the dielectric constant of the gate insulating layer 23 by the source follower. That is, the source voltage when the light detection structure 100A is regarded as a transistor shows a change according to a change in illuminance to the light detection structure 100A. Therefore, light can be detected by detecting a change in the source voltage by an appropriate detection circuit. The output signal from the light detection structure 100A may be in the form of a voltage change or a current change.

  What should be noted here is that a bias voltage in the third voltage range is applied to the photoelectric conversion layer 23p when detecting light. In a conventional optical sensor using a photodiode (or photoelectric conversion film), generally, a light detection operation is performed under a reverse bias corresponding to the first voltage range shown in FIG. Therefore, holes and electrons generated by photoelectric conversion move toward the cathode and anode of the photodiode, respectively. In light detection of a conventional optical sensor using a photodiode (or photoelectric conversion film), electric charges generated by photoelectric conversion are taken out as a signal to an external circuit.

  On the other hand, in the typical example of the light detection device of the present disclosure, a bias voltage in the third voltage range is applied to the photoelectric conversion layer 23p when detecting light. The first bias voltage applied to the transparent gate electrode 22g via the gate voltage control line 48 is, for example, 2.5V, and the second bias voltage applied to the impurity region 20d via the power supply line 42 is For example, 2.4V. When the photoelectric conversion layer 23p is irradiated with light in a state where a bias voltage in the third voltage range is applied, for example, hole-electron pairs are generated in the photoelectric conversion layer 23p. However, in a state where a bias voltage in the third voltage range is applied, the generated holes and electrons are separated and do not move to the electrode and form a dipole. That is, the generated holes and electrons themselves are not taken out of the photoelectric conversion layer 23p.

  The discharge of charge from the photoelectric conversion layer and the flow of charge into the photoelectric conversion layer are slow (about several tens of milliseconds). Therefore, in application to an image sensor, in a configuration that involves discharge of charge from the photoelectric conversion layer or inflow of charge to the photoelectric conversion layer, voltage application to the photoelectric conversion layer at the start of imaging, light irradiation, etc. Noise and afterimages may occur. In the configuration in which the bias voltage applied to the photoelectric conversion layer 23p when detecting light is a voltage in the third voltage range, there is no discharge of charge from the photoelectric conversion layer or inflow of charge to the photoelectric conversion layer. Generation of noise and afterimage can be suppressed.

  In addition, in a state where a bias voltage in the third voltage range is applied, when light is no longer incident on the photoelectric conversion layer 23p, the hole-electron pair is rapidly recombined (less than several tens of microseconds) and disappears. To do. Therefore, according to the embodiment of the present disclosure, it is possible to realize a high-speed response. Since a high-speed response can be realized, the photodetection device according to the embodiment of the present disclosure is advantageous for application to distance measurement using a time-of-flight method, ultrahigh-speed imaging, and the like.

  As described above, according to the embodiment of the present disclosure, it is possible to realize a photodetection device that responds quickly to changes in illuminance. By using two or more types of photoelectric conversion materials having different absorption peaks as the photoelectric conversion material for forming the photoelectric conversion layer 23p, for example, the photoelectric conversion layer 23p has sensitivity in two or more wavelength ranges and is high-speed with respect to changes in illuminance. A detection cell that exhibits a good response can be realized. The first and second photoelectric conversion materials are not limited to the materials described above. Any material that can exhibit a change in dielectric constant upon incidence of light can be used as the first and second photoelectric conversion materials.

  The photodetector 1000 can be manufactured using a general semiconductor manufacturing process. In particular, when a silicon substrate is used as the semiconductor substrate 20, the photodetector 1000 can be manufactured by using various silicon semiconductor processes. Since the light detection structure 100A has a device structure similar to a field effect transistor, it is relatively easy to form another transistor and the light detection structure 100A on the same semiconductor substrate.

(Second Embodiment of Photodetector)
FIG. 10 schematically illustrates a cross-section of a light detection device according to the second embodiment of the present disclosure. In the second embodiment, the light detection apparatus 1000 includes a plurality of detection cells 10B each having a light detection structure 100B. In FIG. 10, the cross section of three detection cell 10Ba-10Bc arrange | positioned along the row direction of a photosensor array is shown.

  In the configuration illustrated in FIG. 10, the light detection structure 100B includes a capacitance modulation transistor 60 and a photoelectric conversion unit 27B. The capacitance modulation transistor 60 is a field effect transistor formed on the semiconductor substrate 20. The capacitance modulation transistor 60 includes impurity regions 20d and 20s, an insulating layer 23x on the semiconductor substrate, and a gate electrode 24 on the insulating layer 23x. The impurity region 20d functions as a drain region (or source region) of the capacitance modulation transistor 60, and the impurity region 20s functions as a source region (or drain region) of the capacitance modulation transistor 60. Similar to the first embodiment, the impurity region 20d is configured to be able to apply a predetermined voltage (second bias voltage) during the operation of the photodetector 1000 by having a connection with the power supply wiring 42. . The insulating layer 23 x functions as a gate insulating layer of the capacitance modulation transistor 60. The insulating layer 23x is, for example, a silicon thermal oxide film.

  The photoelectric conversion unit 27B includes a pixel electrode 21, a transparent electrode 22 facing the pixel electrode 21, and a photoelectric conversion layer 23p sandwiched therebetween. The pixel electrode 21 is electrically separated from the pixel electrodes 21 in the other detection cells 10B by being spatially separated from the adjacent detection cells 10B. The pixel electrode 21 is typically a metal electrode or a metal nitride electrode. Examples of the material for forming the pixel electrode 21 are Al, Cu, Ti, TiN, Ta, TaN, Mo, Ru, and Pt. The pixel electrode 21 may be formed of polysilicon or the like to which conductivity is imparted by doping impurities. Here, a TiN electrode is used as the pixel electrode 21. By forming the pixel electrode 21 as a light-shielding electrode, it is possible to suppress stray light from entering the channel region of the capacitance modulation transistor 60 and / or the channel region of the address transistor 30.

  In this example, the photoelectric conversion layer 23p is formed over the other detection cells 10B. In other words, in the configuration illustrated in FIG. 10, the photoelectric conversion layer 23p in each of the detection cells 10Ba, 10Bb, and 10Bc is a part of a single continuous layer. By forming the photoelectric conversion layers 23p of the plurality of detection cells 10B in the form of a continuous single layer, the manufacturing process is simplified compared to the case where the photoelectric conversion layers 23p are formed separately for each detection cell 10B. Can be The thickness of the photoelectric conversion layer 23p can be, for example, about 200 nm.

  In this example, the transparent electrode 22 is also formed over the other detection cells 10B using TCO, similarly to the transparent gate electrode 22g in the first embodiment. The transparent electrode 22 is connected to a gate voltage control line 48 (not shown in FIG. 10, refer to FIG. 2), and is configured to be able to apply a predetermined voltage (first bias voltage) when the photodetector 1000 is in operation. Has been. That is, the voltage supply circuit 12 (see FIG. 2) is within a predetermined range (for example, the third voltage range described above) with reference to the potential of the impurity region 20d functioning as one of the drain region and the source region of the capacitance modulation transistor 60. ) Can be applied to the transparent electrode 22. Here, since the transparent electrode 22 is formed over the plurality of detection cells 10B, a common first bias voltage can be collectively applied to the plurality of detection cells 10A via the gate voltage control line 48. It is. Further, by forming the transparent electrodes 22 of the plurality of detection cells 10B in the form of a continuous single electrode, it is possible to avoid complication of the manufacturing process.

  In the illustrated example, the transparent electrode 22 and the photoelectric conversion layer 23p are arranged on the interlayer insulating layer 50, and the pixel electrode 21 of the photoelectric conversion unit is connected to a part of the multilayer wiring 40 and the connection unit 54 including the contact plug 52. The gate electrode 24 of the capacitance modulation transistor 60 is connected to each other. The photodetection structure 100B according to the second embodiment is schematically configured such that an electrode (here, connected) is provided between the photoelectric conversion layer 23p and the insulating layer 23x in the photodetection structure 100A (see FIG. 1) according to the first embodiment. It can be said that it has a structure in which the portion 54 and the gate electrode 24) are interposed. Note that the capacitance modulation transistor 60 can also be regarded as including a gate including a series connection of a capacitor having the insulating layer 23x as a dielectric layer and a capacitor having the photoelectric conversion layer 23p as a dielectric layer. In this case, the laminated structure of the insulating layer 23x and the photoelectric conversion layer 23p having the gate electrode 24 therebetween constitutes a gate capacitance (may be referred to as a gate insulating layer) in the capacitance modulation transistor 60, and the transparent electrode 22 It can be said that the gate electrode in the capacitance modulation transistor 60 is configured.

  The principle of light detection in the second embodiment is almost the same as in the first embodiment. That is, by applying the first and second bias voltages to the transparent electrode 22 and the impurity region 20d, respectively, a predetermined bias (typically a voltage in the third voltage range) is applied between the main surfaces of the photoelectric conversion layer 23p. ) Is given. Light enters the photoelectric conversion layer 23p through the transparent electrode 22 in a state where the potential difference between the transparent electrode 22 and the impurity region 20d is kept constant.

  When light enters the photoelectric conversion layer 23p, for example, hole-electron pairs are generated in the photoelectric conversion layer 23p, and the dielectric constant between the pixel electrode 21 and the transparent electrode 22 changes. As the dielectric constant between the pixel electrode 21 and the transparent electrode 22 changes, the effective gate voltage of the capacitance modulation transistor 60 changes, and the threshold voltage in the capacitance modulation transistor 60 changes. The voltage or current from the impurity region 20s changes due to the change in threshold value. Therefore, it is possible to detect a change in illuminance, for example, in the form of a change in voltage on the vertical signal line 46.

  As already described, the photoelectric conversion layer 23p includes the first and second photoelectric conversion materials having different absorption peaks. Therefore, the above-described change in dielectric constant occurs in a wider wavelength range than when a single photoelectric conversion material is used. According to the second embodiment of the present disclosure, using the change in the dielectric constant between the pixel electrode 21 and the transparent electrode 22, for example, light in two different wavelength ranges, as in the first embodiment. Can be detected.

  In the example shown in FIG. 10, a band filter 26 is further disposed between the transparent electrode 22 and the microlens 28. The first filter 26a, the second filter 26b, and the third filter 26c of the band filter 26 face the transparent electrode 22 of the detection cell 10Ba, the transparent electrode 22 of the detection cell 10Bb, and the transparent electrode 22 of the detection cell 10Bc, respectively. By making the transmission characteristics of the first filter 26a, the second filter 26b, and the third filter 26c different from each other, light in the first, second, and third wavelength ranges is selectively incident on the detection cells 10Ba to 10Bc, respectively. be able to.

  As described above, the first filter 26a, the second filter 26b, and the third filter 26c are, for example, colors that selectively transmit light in the red (R), green (G), and blue (B) wavelength ranges, respectively. Can be a filter. In this case, red light, green light, and blue light can be detected by the detection cells 10Ba, 10Bb, and 10Bc, respectively. Alternatively, at least one of the first filter 26a, the second filter 26b, and the third filter 26c may be an IR filter that transmits light having a wavelength of 780 nm or more, for example. For example, if an IR filter is used for the first filter 26a, infrared light can be detected by the detection cell 10Ba.

At least one of the first, second and third wavelength ranges may be a wavelength range including a peak wavelength in the first photoelectric conversion material or a peak wavelength in the second photoelectric conversion material. For example, as the first photoelectric conversion material and the second photoelectric conversion material, subphthalocyanine and C ₆₀ are used, respectively, and as the second filter 26b and the third filter 26c, a G filter and a blue color that selectively transmit green light, respectively. A B filter that selectively transmits light may be used. Alternatively, tin naphthalocyanine and C ₆₀ may be used as the first photoelectric conversion material and the second photoelectric conversion material, respectively, and an IR filter and a B filter may be used as the second filter 26b and the third filter 26c, respectively.

  According to the second embodiment, since the photoelectric conversion layer 23p is disposed on the interlayer insulating layer 50, compared to the structure in which the photoelectric conversion layer 23p is embedded in the interlayer insulating layer 50 (see FIG. 1), a multilayer structure is provided. The degree of freedom of layout of various wirings in the wiring 40 is improved. In the configuration illustrated in FIG. 10, when the detection cell 10B is viewed from the normal direction of the semiconductor substrate 20, the ratio of the region where the pixel electrode 21 and the transparent electrode 22 overlap to the detection cell 10B is the aperture ratio in the detection cell 10B. It corresponds to. Therefore, it is easy to obtain a larger aperture ratio than a structure in which the photoelectric conversion layer 23p is embedded in the interlayer insulating layer 50 (see FIG. 1).

  In addition, it is less difficult to manufacture the photoelectric conversion layer 23p on the interlayer insulating layer 50 than in the case where the photoelectric conversion layer 23p is embedded in the interlayer insulating layer 50, which is advantageous in terms of manufacturing. For example, if the gate electrode 24 of the capacity modulation transistor 60 and the gate electrode 34 of the address transistor 30 are both polysilicon electrodes, the gate of the address transistor 30 can be formed simultaneously with the formation of the gate of the capacity modulation transistor 60.

  For example, in order to form the gate electrode 24 of the capacitance modulation transistor 60 and the gate electrode 34 of the address transistor 30 using different materials, it is necessary to form them sequentially. When the lithography technique is applied to form the gate electrode 24 and the gate electrode 34 or when impurities are implanted, it is generally difficult to avoid an alignment shift between the gate electrode 24 and the gate electrode 34. Therefore, when the gate electrode 24 of the capacitance modulation transistor 60 and the gate electrode 34 of the address transistor 30 are formed using different materials, it is necessary to ensure a margin in alignment. In other words, it is disadvantageous for miniaturization of the detection cell in the photodetection device.

  As illustrated in FIG. 10, by making the gate electrode 24 in the capacitance modulation transistor 60 and the gate electrode 34 in the address transistor 30 in the same layer (common level), using a common mask and a common material, These can be collectively arranged in a desired position and shape without taking into account the alignment shift. Similarly, by taking the insulating layer 23x at the gate of the capacitance modulation transistor 60 and the gate insulating layer 33 at the address transistor 30 as the same layer, a shift in alignment is taken into account using a common mask and a common material. Instead, they can be collectively arranged in a desired position and shape. Therefore, a finer pixel can be formed. By making the gate structure of the capacitance modulation transistor 60 and the gate structure of the address transistor 30 common, the manufacturing cost can be further reduced.

  In the first embodiment described above, the light detection structure 100A does not have an electrode corresponding to the gate electrode 24 in the capacitance modulation transistor 60 (see FIG. 1). However, it is possible to form the insulating layer 23x in the photodetection structure 100A and the gate insulating layer 33 in the address transistor 30 by using a common mask and a common material. Thereby, the alignment for forming the gate insulating layer 33 after the formation of the insulating layer 23x or the alignment for forming the insulating layer 23x after the formation of the gate insulating layer 33 can be eliminated. Therefore, the insulating layer 23x and the gate insulating layer 33 are made the same layer, and the positional shift between the insulating layer 23x and the gate insulating layer 33 can be eliminated.

  Note that the device structure illustrated in FIG. 10 is similar to the device structure of a stacked image sensor in which a photoelectric conversion layer is disposed on a semiconductor substrate. However, in the stacked image sensor, holes generated in the photoelectric conversion layer by light irradiation are applied by applying a relatively high bias voltage between the pixel electrode and the transparent electrode facing the pixel electrode. One of the electrons and electrons is collected as a signal charge on the pixel electrode. The collected signal charge is temporarily accumulated in the floating diffusion in the unit pixel cell, and a signal voltage corresponding to the accumulated charge amount is read at a predetermined timing.

  On the other hand, in the light detection structure of the present disclosure, typically, the positive and negative charges (for example, holes and electrons) generated in the photoelectric conversion layer 23p are not moved toward the electrode, but the photoelectric conversion layer. The electrical signal corresponding to the change in the dielectric constant of 23p (between the pixel electrode 21 and the transparent electrode 22 in the example of FIG. 10) is read. In a stacked image sensor, only one of holes and electrons can be used as a signal charge, whereas in the photodetection structure of the present disclosure, positive and negative charges (for example, holes and electrons) are paired. It is used to change the threshold. Therefore, higher sensitivity can be realized. Further, assuming that the potential difference applied between the upper surface and the lower surface of the photoelectric conversion layer 23p is the potential difference in the third voltage range described above, generated positive and negative charges (for example, holes and electrons) when the light irradiation is stopped. Pairs will recombine promptly. That is, unlike the stacked image sensor, the pixel electrode potential resetting operation is unnecessary. Note that the light detection structure of the present disclosure does not perform the operation of accumulating holes or electrons generated in the photoelectric conversion layer 23p as signal charges in the floating diffusion. Therefore, unlike the stacked image sensor, the semiconductor substrate 20 does not have a charge storage region for storing signal charges.

  As described above, when the potential difference applied between the upper surface and the lower surface of the photoelectric conversion layer 23p is the potential difference in the third voltage range described above, when the light irradiation is stopped, a pair of generated positive and negative charges is generated. Can recombine quickly. This means that the output of the light detection structure shows fluctuations according to changes in illuminance during light irradiation, and does not depend on the integrated light quantity. Therefore, when the potential difference applied between the upper surface and the lower surface of the photoelectric conversion layer 23p is set to the potential difference in the third voltage range described above, the exposure timing and the signal readout timing are basically matched. .

  A capacitor in which one electrode is electrically connected to the impurity region 20s or 30s (for example, see FIG. 10) of the semiconductor substrate 20 may be provided in the detection cell. By disposing such a capacitor in the detection cell, it becomes possible to read the output signal at a timing different from the exposure for the light detection structure.

  FIG. 11 shows a modification of the light detection apparatus 1000. In the configuration illustrated in FIG. 11, the light detection apparatus 1000 includes a plurality of detection cells 10C (here, detection cells 10Ca, 10Cb, and 10Cc) each having a light detection structure 100C. The difference between the photoelectric conversion unit 27C of the light detection structure 100C shown in FIG. 11 and the photoelectric conversion unit 27B of the light detection structure 100B described with reference to FIG. 10 is that the photoelectric conversion unit 27C has the photoelectric conversion layer 23p. And an electrode (pixel electrode 21 and / or transparent electrode 22).

  In the configuration illustrated in FIG. 11, insulating layers 29 a and 29 b are disposed between the pixel electrode 21 and the photoelectric conversion layer 23 p and between the photoelectric conversion layer 23 p and the transparent electrode 22, respectively. As a material constituting the insulating layers 29a and 29b, for example, a material having a smaller leakage current than a material constituting the photoelectric conversion layer 23p can be selected. For example, a silicon oxide film, a silicon nitride film, an aluminum oxide film, or the like can be used.

The arrangement of the insulating layer between the pixel electrode 21 and the photoelectric conversion layer 23p and at least one between the photoelectric conversion layer 23p and the transparent electrode 22 is a photoelectric conversion of a photoelectric conversion material having absorption in the near infrared region. This is particularly effective when used for the layer 23p. The photoelectric conversion material having absorption in the near infrared region has a narrow band gap, and the magnitude of the leakage current in the organic photoelectric conversion layer alone under a bias voltage of 0.1 V is 1 × 10 ⁻⁸ A / cm. ^{Can be on the} order of ² . When a narrow band gap material is used as the first photoelectric conversion material or the second photoelectric conversion material and a large bias is applied between the main surfaces of the photoelectric conversion layer 23p, the photoelectric conversion layer 23p is supplied to or from the photoelectric conversion layer 23p. Leakage current may occur, and a sufficient S / N ratio may not be ensured. By disposing an insulating layer on at least one main surface side of the photoelectric conversion layer 23p, such a leakage current can be reduced and a necessary S / N ratio can be ensured. In the light detection structure 100A illustrated in FIG. 1, the insulating layer 23x disposed between the photoelectric conversion layer 23p and the semiconductor substrate 20 contributes to the reduction of such a leakage current.

  In the configuration illustrated in FIG. 11, the insulating layers 29a and 29b are disposed between the pixel electrode 21 and the photoelectric conversion layer 23p and between the photoelectric conversion layer 23p and the transparent electrode 22, respectively. A large bias voltage can be applied between the drain region (or source region) of the capacitance modulation transistor 60 and the transparent electrode 22. For example, the voltage supply circuit 12 may give a potential difference in the first voltage range between the drain region (or source region) of the capacitance modulation transistor 60 and the transparent electrode 22. In other words, when detecting light, a potential difference in the first voltage range may be applied between the main surfaces of the photoelectric conversion layer 23p instead of the potential difference in the third voltage range. For example, a voltage of 3.7 V as the first bias voltage and a voltage of 1.2 V as the second bias voltage may be applied to the impurity region 20 d and the transparent electrode 22, respectively.

  When light is irradiated onto the photoelectric conversion layer 23p in a state where a bias voltage in the first voltage range (see FIG. 9) is applied to the photoelectric conversion layer 23p, positive and negative charges (for example, holes) generated by the photoelectric conversion are generated. And one of electrons) moves toward the transparent electrode 22, and the other moves toward the pixel electrode 21. In this way, when a bias voltage in the first voltage range is applied to the photoelectric conversion layer 23p, positive and negative charges generated by photoelectric conversion can be separated. The time until the pair of charges is recombined is longer than when a bias voltage in the third voltage range is applied to the photoelectric conversion layer 23p. Therefore, it is not always necessary to match the exposure timing with the signal readout timing. Since it is relatively easy to make the exposure timing different from the signal readout timing, in one aspect, application of the bias voltage in the first voltage range to the photoelectric conversion layer 23p is advantageous for application to an image sensor. It is.

  In a state where a bias voltage in the first voltage range is applied to the photoelectric conversion layer 23p, the insulating layer 29a between the photoelectric conversion layer 23p and the pixel electrode 21 has positive and negative charges (for example, positive charges) generated by photoelectric conversion. It can function as a capacitor that stores one of holes and electrons). As the charge is accumulated in the capacitor, electrostatic induction occurs in the connection portion 54, and the effective gate voltage in the capacitance modulation transistor 60 changes. After the reading of the output signal is completed, for example, a voltage having a polarity opposite to the first bias voltage is applied to the transparent electrode 22 to reset the charge accumulated in the insulating layer 29a as a capacitor. A reset operation is performed. Of course, the light detection operation may be performed in a state where the bias voltage in the third voltage range is applied to the photoelectric conversion layer 23p. In this case, the reset operation is not necessary.

  Thus, an insulating layer may be disposed between the photoelectric conversion layer 23p and the pixel electrode 21 and between the photoelectric conversion layer 23p and the transparent electrode 22. In the case where the potential difference between the impurity region 20d and the transparent electrode 22 is increased by disposing an insulating layer between the photoelectric conversion layer 23p and the pixel electrode 21 and between the photoelectric conversion layer 23p and the transparent electrode 22. Even if it exists, the movement to the exterior of the photoelectric converting layer 23p of the electric charge produced | generated by photoelectric conversion can be suppressed. Therefore, afterimage generation can be suppressed. In addition, from the viewpoint of suppressing the movement of charges to the outside of the photoelectric conversion layer 23p, insulation is provided between at least one of the photoelectric conversion layer 23p and the pixel electrode 21 and between the photoelectric conversion layer 23p and the transparent electrode 22. A layer may be disposed.

  In each of the above-described embodiments, the example in which each of the capacitance modulation transistor 60 and the address transistor 30 is an N-channel MOS has been described. However, the transistors in the embodiments of the present disclosure are not limited to N-channel MOS. The capacitance modulation transistor 60 and the address transistor 30 may be an N-channel MOS or a P-channel MOS. Further, these need not be unified with either the N-channel MOS or the P-channel MOS. As the address transistor 30, a bipolar transistor can be used in addition to the FET. The carriers in the channel formed between the impurity regions 20d and 20s of the light detection structure 100A described above may be electrons or holes.

  A sample in which a layer of a photoelectric conversion material was formed on a glass substrate was prepared, and the change in capacitance value due to light irradiation on the sample was measured to evaluate the characteristics of the photoelectric conversion layer.

Example 1
The sample of Example 1 was produced by the following procedure. First, a glass substrate was prepared. Next, ITO, aluminum oxide, subphthalocyanine as the first photoelectric conversion material, C ₆₀ as the second photoelectric conversion material, aluminum oxide, and ITO were sequentially deposited on the glass substrate. Thereby, as schematically shown in FIG. 12, the photoelectric conversion layer in which the glass substrate GS, the first electrode E1, the insulating layer D1, the layer P1 of the first photoelectric conversion material, and the layer P2 of the second photoelectric conversion material are stacked. Sample SE1 of Example 1 having a laminated structure of PL, insulating layer D2, and second electrode E2 was obtained. Magnetron sputtering was applied to form the first electrode E1 and the second electrode E2, and atomic layer deposition was applied to the formation of the insulating layers D1 and D2. Vacuum deposition was applied to the deposition of the first and second photoelectric conversion materials. The thicknesses of the first electrode E1, the insulating layer D1, the first photoelectric conversion material layer P1, the second photoelectric conversion material layer P2, the insulating layer D2, and the second electrode E2 are 150 nm, 20 nm, 75 nm, and 75 nm, respectively. 20 nm and 30 nm.

(Example 2)
As the photoelectric conversion layer PL, Suzuna phthalocyanine and C ₆₀ codeposited with the bulk layer (thickness: 50 nm, volume Suzuna phthalocyanine and C ₆₀ ratio: 1: 1) was formed, it was not formed insulating layer D2 A sample of Example 2 was produced in the same manner as Example 1 except that an Al layer (thickness: 80 nm) was formed as the second electrode E2.

(Comparative Example 1)
A sample of Comparative Example 1 was produced in the same manner as in Example 1 except that the second photoelectric conversion material layer P2 was not formed.

(Evaluation)
About each sample of Example 1, 2 and the comparative example 1, the characteristic of the photoelectric converting layer was evaluated by the comparison of the capacitance value at the time of light irradiation and the time of light non-irradiation (dark state). The capacitance value in each sample was measured by connecting a 4284A Precision LCR meter manufactured by Keysight Technology, Inc. to the first electrode E1 and the second electrode E2.

  First, regarding Example 1 and Comparative Example 1, for each of white light, red light, green light, and blue light, changes in capacitance values during light irradiation and in a dark state were measured. In the measurement of the capacitance value at the time of light irradiation, a white LED (power consumption: about 7 mW) was arranged on the second electrode E2 side of the sample, and the photoelectric conversion layer was irradiated with light. In the irradiation of red light, green light, and blue light, a red transmission color filter (transmission wavelength: 630 nm to 730 nm), a green transmission color filter (transmission wavelength: 630 nm to 730 nm) manufactured by ZWO, between the white LED and the second electrode E2. A transmission wavelength: 490 nm to 550 nm) and a blue transmission color filter (transmission wavelength: 400 nm to 490 nm) were respectively inserted.

  Table 1 below shows the capacity change rate obtained by the measurement. The capacitance value was measured in a state where a potential difference (reverse bias) of 6 V was applied between the first electrode E1 and the second electrode E2. The capacitance change rate in Table 1 means the ratio of the measured capacitance value during light irradiation to the measured capacitance value in the dark state.

  As shown in Table 1, when white light is incident, a relatively large capacity change rate is obtained in both the sample of Example 1 and the sample of Comparative Example 1. That is, by applying the same configuration as the configuration of the photoelectric conversion layer in the sample of Example 1 or Comparative Example 1 to the photoelectric conversion layer 23p of the photodetecting device 1000, white light is detected using a change in dielectric constant. It turns out that it is possible.

  In the sample of Comparative Example 1, although a capacity change rate of 1.09 times and 1.07 times was obtained for green light and blue light, respectively, a capacity change rate larger than 1 time was obtained for red light. Not obtained. This is because subphthalocyanine hardly absorbs light having a wavelength of 620 nm or more (see FIG. 7). The reason why the capacity change rate of 1.07 times with respect to blue light is obtained is that the absorption spectrum of subphthalocyanine starts to rise from around 470 nm as shown in FIG. From Table 1, it can be seen that a higher capacity change rate is obtained for green light than for blue light. This is consistent with the absorption in subphthalocyanine being greater in the green wavelength range than in blue.

On the other hand, in the sample of Example 1, a capacity change rate of 1.07 times was also obtained for red light. That is, it can be seen that the detectable wavelength range is expanded as compared with the case where a single photoelectric conversion material is used. Despite the fact that subphthalocyanine hardly absorbs light having a wavelength of 620 nm or more, it exhibits a capacity change rate of 1.07 times the incidence of red light, which is the C ₆₀ used as the second photoelectric conversion material. However, this is considered to be because absorption is also observed in the vicinity of a wavelength of 700 nm. In the sample of Example 1, a higher capacity change rate than that of the sample of Comparative Example 1 was obtained for green light and blue light. This is thought to be because C ₆₀ exhibits absorption over the visible light range.

  As described above, in the sample of Example 1, a relatively high capacity change rate is obtained even when any of red light, green light, and blue light is selectively irradiated using the color filter. It can be seen that the wavelength range to be detected can be switched using the color filter. That is, it can be seen that by using two or more kinds of photoelectric conversion materials having different absorption peaks, it is possible to expand the detectable wavelength range by utilizing the change in dielectric constant. Therefore, for example, it can be seen that an RGB color image sensor can be provided.

  Next, regarding Example 2, the near-infrared wavelength of about 940 nm was measured for the change in capacitance value during light irradiation and in the dark state. In the measurement of the capacitance value at the time of light irradiation, a light source was arranged on the first electrode E1 side of the sample, and the near infrared ray was irradiated to the photoelectric conversion layer through the glass substrate GS. In the measurement, the potential difference between the first electrode E1 and the second electrode E2 was set to 0 V, the electric power supplied to the light source was changed, and the capacity change rate was obtained for each input electric power.

  Table 2 below shows the capacity change rate obtained by the measurement. The capacity change rate in Table 2 means the ratio of the measured value of the capacity when irradiated with near infrared rays to the measured value of the capacity in the dark state.

  It can be seen from Table 2 that a capacity change rate greater than 1 can be obtained by irradiation with near infrared rays. It can also be seen that the rate of change in capacity also increases as the power supplied to the light source increases. In this example, the capacity modulation of 7% is obtained by increasing the input power to about 4 mW, and the capacity modulation of about 34% is obtained when the input power is 69 mW. That is, it can be seen that a change in dielectric constant according to the illuminance occurs between the first electrode E1 and the second electrode E2. Therefore, for example, by applying a configuration similar to the configuration of the photoelectric conversion layer in the sample of Example 2 to the photoelectric conversion layer 23p of the photodetecting device 1000, information on near-infrared illuminance is obtained using a change in dielectric constant. It turns out that it is possible.

Further, from the results shown in Table 1, in the sample of Example 2 using tin naphthalocyanine and C ₆₀ as the first and second photoelectric conversion materials, the capacity modulation according to the illuminance is also applied to visible light (particularly blue light). Can be expected to occur. That is, by combining a photoelectric conversion material having absorption in the infrared region with a photoelectric conversion material having absorption in the visible region, infrared and visible light can be detected using changes in dielectric constant.

  Embodiments of the present disclosure are applicable to a light detection device, an image sensor, and the like. By appropriately selecting the material of the photoelectric conversion layer, for example, it is possible to acquire an image using visible light and infrared rays. The light detection device of the present disclosure can be used for, for example, a digital camera, a security camera, a camera mounted on a vehicle, and the like. The vehicle-mounted camera can be used, for example, as an input to the control device for the vehicle to travel safely. Alternatively, it can be used for assistance of an operator for the vehicle to travel safely.

10A to 10C Detection cell 12 Voltage supply circuit 14 Vertical scanning circuit 20 Semiconductor substrate 20d, 20s, 30s Impurity region 20t Element isolation region 21 Pixel electrode 22 Transparent electrode 22g Transparent gate electrode 23 Gate insulating layer 23p Photoelectric conversion layer 23x Insulating layer 24 Gate Electrode 25a, 25b Protective layer 26 Band filter 26a First filter 26b Second filter 26c Third filter 27B, 27C Photoelectric conversion unit 29a, 29b Insulating layer 30 Address transistor 30s Impurity region 54 Connection unit 60 Capacitance modulation transistor 100A to 100C Photodetection Structure 120s Laminated structure 120t Photoelectric conversion structure 122m Mixed layer 1000 Photodetector

Claims (21)

Each is
A source region and a drain region formed in a semiconductor substrate;
A gate insulating layer on the semiconductor substrate;
A transparent gate electrode on the gate insulating layer;
Having a plurality of detection cells,
The gate insulating layer has a photoelectric conversion layer including a first photoelectric conversion material and a second photoelectric conversion material having absorption peaks different from each other,
Each of the plurality of detection cells outputs an electric signal corresponding to a change in dielectric constant of the photoelectric conversion layer, which is generated by light incident on the photoelectric conversion layer through the transparent gate electrode, in the source region and the drain region. Output from one of the two.   The photodetecting device according to claim 1, wherein the gate insulating layer includes an insulating layer disposed between the photoelectric conversion layer and the semiconductor substrate.   The photodetecting device according to claim 1, further comprising a light shielding film disposed between the transparent gate electrode and the semiconductor substrate. A bandpass filter including a first filter and a second filter having different wavelength ranges to be transmitted;
The plurality of detection cells include a first detection cell and a second detection cell;
The first filter is opposed to the transparent gate electrode of the first detection cell;
4. The photodetecting device according to claim 1, wherein the second filter faces a transparent gate electrode of the second detection cell. 5.   The light detection device according to claim 4, wherein each of the transparent gate electrode of the first detection cell and the transparent gate electrode of the second detection cell is a part of a single continuous electrode. The photoelectric conversion layer includes a first voltage range in which an absolute value of an output current density increases as the reverse bias voltage increases, a second voltage range in which an output current density increases as the forward bias voltage increases, and the first In the third voltage range between the voltage range and the second voltage range, the change rate of the output current density with respect to the bias voltage has different photocurrent characteristics,
6. The photodetecting device according to claim 1, wherein the change rate in the third voltage range is smaller than the change rate in the first voltage range and the change rate in the second voltage range. A voltage supply circuit for supplying a gate voltage within the third voltage range to the transparent gate electrode when the other potential of the source region and the drain region is used as a reference;
Each of the plurality of detection cells includes the photoelectric conversion layer in a state where a potential difference between the other of the source region and the drain region and the transparent gate electrode is maintained within the third voltage range. The light detection device according to claim 6, wherein an electrical signal corresponding to a change in dielectric constant is output from the one of the source region and the drain region. Each is
A first electrode;
A field effect transistor formed on a semiconductor substrate, the field effect transistor having a gate electrically connected to the first electrode;
A translucent second electrode facing the first electrode;
A photoelectric conversion layer disposed between the first electrode and the second electrode;
Having a plurality of detection cells,
The photoelectric conversion layer includes a first photoelectric conversion material and a second photoelectric conversion material having absorption peaks different from each other,
The photoelectric conversion layer includes a first voltage range in which an absolute value of an output current density increases as the reverse bias voltage increases, a second voltage range in which an output current density increases as the forward bias voltage increases, and the first In the third voltage range between the voltage range and the second voltage range, the change rate of the output current density with respect to the bias voltage has different photocurrent characteristics,
The rate of change in the third voltage range is smaller than the rate of change in the first voltage range and the rate of change in the second voltage range,
In each of the plurality of detection cells, a potential difference between one of a source and a drain of the field effect transistor and the second electrode is maintained within the first voltage range or the third voltage range. In the state, an electric signal corresponding to a change in dielectric constant between the first electrode and the second electrode, which is caused by light incident on the photoelectric conversion layer through the second electrode, is transmitted between the source and the drain. Photodetector that outputs from the other of them.   9. The apparatus according to claim 8, further comprising at least one insulating layer disposed between the first electrode and the photoelectric conversion layer and at least one of the photoelectric conversion layer and the second electrode. Photodetector.   The photodetection according to claim 9, further comprising a voltage supply circuit that supplies a voltage within the first voltage range to the second electrode when the potential of the one of the source and the drain is used as a reference. apparatus.   10. The voltage supply circuit according to claim 8, further comprising a voltage supply circuit that supplies a voltage within the third voltage range to the second electrode when the potential of the one of the source and the drain is used as a reference. Photodetector.   The photodetecting device according to claim 8, wherein the first electrode is a light-shielding electrode. The gate of the field effect transistor includes a gate insulating layer and a gate electrode provided on the semiconductor substrate,
The photodetecting device according to claim 8, wherein the first electrode has a connection portion that connects the gate electrode and the first electrode. A bandpass filter including a first filter and a second filter having different wavelength ranges to be transmitted;
The plurality of detection cells include a first detection cell and a second detection cell;
The first filter is opposed to the second electrode of the first detection cell;
The photodetection device according to claim 8, wherein the second filter is opposed to the second electrode of the second detection cell.   The optical detection device according to claim 14, wherein each of the second electrode of the first detection cell and the second electrode of the second detection cell is a part of a single continuous electrode.   The photodetection device according to claim 14 or 15, wherein each of the photoelectric conversion layer of the first detection cell and the photoelectric conversion layer of the second detection cell is a part of a single continuous layer.   The first filter selectively transmits light in a first wavelength range of visible light, and the second filter selectively transmits light in a second wavelength range of visible light. The photodetection device according to any one of 4, 5, 14, 15 and 16.   The first filter selectively transmits light in a first wavelength range of visible light, and the second filter selectively transmits infrared light in a second wavelength range. , 15 or 16.   The photodetection device according to claim 17 or 18, wherein an absorption peak of the first photoelectric conversion material is in the first wavelength range.   The photodetection device according to claim 17, wherein an absorption peak of the second photoelectric conversion material is in the second wavelength range.   21. The light detection device according to claim 1, wherein the photoelectric conversion layer has a stacked structure of the first photoelectric conversion material and the second photoelectric conversion material.

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