JP2017028114A - Photodetector, photodetection device, solid-state image pickup device and camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photodetector and a solid image pickup device that has high sensitivity to ultraviolet light, and a camera system using the same.SOLUTION: A photodetector includes a lower electrode 106, a light absorbing layer 104 disposed on the lower electrode 106, a transparent electrode 103 disposed on the light absorbing layer 104, and an ultraviolet light transmitting filter 101 disposed on the transparent electrode 103. The light absorbing layer 104 has a maximum absorption coefficient in an ultraviolet light region, and the ultraviolet light transmitting filter 101 has the maximum transmittance in the ultraviolet light region.SELECTED DRAWING: Figure 1A

Description

  The present disclosure relates to a photodetector and a solid-state imaging device that output ultraviolet light as an electrical signal.

  The ultraviolet light detector receives ultraviolet light and detects a current generated by photoelectric conversion. In order to guarantee the sensitivity to light in the ultraviolet region, Patent Document 1 reports a device in which a photoelectric conversion unit is formed using diamond, which is a wide band gap semiconductor material.

  Further, Patent Document 2 reports a type using diamond, which is also a wide bandgap semiconductor material, in a configuration in which the thickness of the electrode covering the photoelectric conversion portion is limited in order to improve photosensitivity.

JP 2006-156464 A JP 2007-66976 A

  However, since the absorption coefficient of diamond for ultraviolet light is low, there is a problem that a highly sensitive ultraviolet light detector cannot be realized.

  The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a photodetector and a solid-state imaging device that are highly sensitive to ultraviolet light.

  In order to solve the above-described problems of the related art, a photodetector according to an embodiment of the present disclosure is disposed on a first electrode, a photoelectric conversion film disposed on the first electrode, and the photoelectric conversion film. A transparent electrode and an ultraviolet light transmission filter disposed on the transparent electrode, the ultraviolet light transmission filter has a maximum transmittance in the ultraviolet light region, and the photoelectric conversion film has a maximum absorption coefficient in the ultraviolet light region. Have

  In the photodetector according to one embodiment of the present disclosure, the ultraviolet light transmission filter may have a maximum transmittance in a wavelength region of 200 nm or more and 300 nm or less.

  In the photodetector according to one embodiment of the present disclosure, the absorption coefficient of the photoelectric conversion film has a first peak in the ultraviolet light region and a second peak smaller than the first peak in the visible light region. You may have.

  In the photodetector according to one embodiment of the present disclosure, the first peak may be an absorption peak derived from a HOMO-LUMO gap, and the second peak may be an absorption peak derived from an exciton peak. .

  In addition, a photodetector according to an embodiment of the present disclosure includes a readout circuit that reads out an output signal from the photodetector, and a control circuit that controls an output operation from the photodetector and a readout operation of the readout circuit. The readout circuit and the control circuit may be formed on the same substrate.

  In addition, a solid-state imaging device according to an embodiment of the present disclosure includes a semiconductor substrate, a plurality of first electrodes that are arranged in an array above the semiconductor substrate, each of which forms a different unit pixel, and a plurality of first electrodes A photoelectric conversion film formed thereon, a transparent electrode formed on the photoelectric conversion film, a plurality of ultraviolet light transmission filters formed on the transparent electrode and corresponding to each of the plurality of first electrodes, and a plurality of A charge storage region that is formed in the semiconductor substrate corresponding to each of the first electrodes, is electrically connected to the corresponding first electrode, and stores charges generated by photoelectric conversion in the photoelectric conversion film, At least some of the plurality of ultraviolet light transmission filters have a maximum transmittance in the ultraviolet light region, and the photoelectric conversion film has a maximum absorption coefficient in the ultraviolet light region.

  In the solid-state imaging device according to one embodiment of the present disclosure, the ultraviolet light transmission filter may have a maximum transmittance in a wavelength region of 200 nm or more and 300 nm or less.

  In the solid-state imaging device according to one embodiment of the present disclosure, the absorption coefficient of the photoelectric conversion film has a first peak in the ultraviolet light region and a second peak smaller than the first peak in the visible light region. You may have.

  In the solid-state imaging device according to one embodiment of the present disclosure, the first peak may be an absorption peak derived from a HOMO-LUMO gap, and the second peak may be an absorption peak derived from an exciton peak. .

  A camera system according to an aspect of the present disclosure includes the solid-state imaging device and an image display unit that displays at least one of an ultraviolet image and a visible light image obtained from the solid-state imaging device.

  In addition, the camera system according to an embodiment of the present disclosure senses ultraviolet light emitted from a flame generated at the time of a fire.

  According to the present disclosure, it is possible to provide a photodetector and a solid-state imaging device that are highly sensitive to ultraviolet light.

1A is a diagram illustrating an example of a basic configuration of a photodetector according to Embodiment 1. FIG. FIG. 1B is a diagram showing the relationship between the transmittance and wavelength of the ultraviolet light transmission filter according to Embodiment 1. FIG. 1C is a diagram showing a relationship between the absorption coefficient and the wavelength of the photoelectric conversion film according to Embodiment 1. FIG. 2 is a block diagram illustrating a configuration of a pixel unit and a signal readout unit of the solid-state imaging device according to the second embodiment. FIG. 3 is a circuit diagram of a pixel portion of the solid-state imaging device according to the second embodiment. FIG. 4 is a device cross-sectional view for three pixels according to the second embodiment. FIG. 5 is a block diagram illustrating a configuration of the flame detection camera according to the third embodiment. FIG. 6A is an image taken by a camera using a solid-state imaging device for visible light. FIG. 6B is an image captured by the flame detection system according to Embodiment 3. FIG. 7 is a block diagram illustrating the configuration of the pixel unit and the signal readout unit of the solid-state imaging device according to the third embodiment. FIG. 8A is a block diagram illustrating a configuration of a flame detection camera according to Embodiment 3. FIG. 8B is a block diagram illustrating a configuration of the flame detection camera according to Embodiment 3.

  Hereinafter, embodiments of a solid-state imaging device according to the present disclosure will be described with reference to the drawings. In addition, although this indication is demonstrated using the following embodiment and attached drawing, this is for the purpose of illustration and this indication is not intended to be limited to these.

(Embodiment 1)
A solid-state imaging device according to Embodiment 1 of the present disclosure will be described with reference to FIGS. 1 to 6.

  First, the overall configuration of the ultraviolet light detection unit according to the first embodiment of the present disclosure will be described.

  FIG. 1A is a basic configuration diagram illustrating an example of an ultraviolet light detection unit according to the first embodiment of the present disclosure. The ultraviolet light detection unit 100 includes an ultraviolet light transmission filter 101, a protective film 102, a conductive transparent electrode 103, a photoelectric conversion film 104, a lower electrode 106, a charge storage unit 107, an amplifier circuit unit 108, and data storage. Part 109.

The ultraviolet light transmission filter 101 has a transmittance in a wavelength region of 200 nm ≦ λ ≦ 300 nm as shown in FIG. 1B, for example, and transmits ultraviolet light having a wavelength λ ≧ 300 nm and a transmittance of less than 0.1%. It is a filter. Generally, ultraviolet light having a wavelength of 300 nm or more is also included in the sunlight spectrum, so that it is necessary to cut it with the ultraviolet light transmission filter 101 in order to distinguish it. Such an ultraviolet light transmission filter can be obtained by, for example, alternately stacking MgF ₂ films and SiO ₂ films using a sputtering method or the like.

The protective film 102 and the conductive transparent electrode 103 are made of a material that efficiently transmits ultraviolet light to the photoelectric conversion film 104 without being attenuated. For example, the protective film 102 is made of SiO ₂ having a high crystal purity, and the conductive transparent electrode 103 is made of ITO (Indium Tin Oxide).

The photoelectric conversion film 104 converts light into signal charges. Specifically, the photoelectric conversion film 104 is formed under the conductive transparent electrode 103 and is composed of organic molecules having high light absorption ability. The organic molecules constituting the photoelectric conversion film 104 is made of, for example, fullerene C _60. Further, the photoelectric conversion film 104 is formed using a vacuum deposition method. For example, as shown in FIG. 1C, the organic molecule has a high light absorption capability over the entire range of ultraviolet light and visible light having a wavelength of 200 nm to 700 nm. Here, the peak in the ultraviolet region is an absorption peak derived from the HOMO (highest occupied orbital) -LUMO (lowest unoccupied orbital) energy gap, and the peak in the visible region is an absorption peak derived from the exciton peak. In general, electron-hole pairs generated by photoexcitation between HOMO-LUMO energy gaps can be separated into electrons and holes relatively easily and can generate a large photocurrent, so that they have very high sensitivity in the ultraviolet region. . The thickness of the photoelectric conversion film 104 is, for example, 500 nm.

  The lower electrode 106 collects electrons generated in the photoelectric conversion film 104, and the collected electrons are accumulated as signal charges in the charge accumulation unit 107. The lower electrode 106 is made of, for example, TiN. The signal charge is amplified by the amplifier circuit 108 and then stored in the data storage unit 109.

  In this specification, the ultraviolet light region means a wavelength band of 100 nm or more and 400 nm or less. In this specification, the visible light region means a wavelength band of 400 nm or more and 800 nm or less.

(Embodiment 2)
FIG. 2 is a block diagram illustrating a configuration of the solid-state imaging apparatus 201 according to Embodiment 2 of the present disclosure. The solid-state imaging device 201 includes a pixel array 202, row signal drive circuits 203a and 203b, a noise canceller circuit 204 including a column amplifier and a noise canceller arranged in each column, a horizontal drive circuit 205, and an output stage amplifier 206. Is provided.

  FIG. 3 is a circuit diagram illustrating an example of the configuration of the pixel 200 of the solid-state imaging device.

  In the pixel portion of the solid-state imaging device, a plurality of pixels 200 are arranged in a matrix of, for example, m rows and n columns (m and n are natural numbers).

  The pixel 200 includes a photoelectric conversion unit 301, a charge storage (floating diffusion: FD) unit 302, an amplification transistor 303, a reset transistor 304, and a selection transistor 305.

  The photoelectric conversion unit 301 generates signal charges corresponding to the amount of incident light by photoelectrically converting incident light.

  The selection transistor 305 has a source terminal connected to the source terminal of the amplification transistor 303 and a drain terminal connected to the column signal line 306.

  The reset transistor 304 has a source terminal connected to the charge storage unit 302 and a drain terminal connected to the power supply line 307.

  FIG. 4 is a cross-sectional view of a region for three pixels of the solid-state imaging device 201. The actual pixels are arranged in the pixel array 202, for example, for 10 million pixels.

  As shown in FIG. 4, the solid-state imaging device 201 includes an ultraviolet light transmission filter 401, a protective film 402, a conductive transparent electrode 403 (second electrode), a photoelectric conversion film 404, an interelectrode insulating film 405, Lower electrode 406 (first electrode), inter-wiring insulating film 407, power feeding layer 408, wiring layer 409, substrate 410, well 411, STI region (shallow trench isolation region) 412, and interlayer insulating layer 413 A contact plug 414, a charge storage region 415, a reset transistor 416, and an amplification transistor 417.

  The substrate 410 is a semiconductor substrate, for example, a silicon substrate.

  The conductive transparent electrode 403 is formed over the entire surface of the pixel array 302 under the protective film 402. The conductive transparent electrode 403 transmits visible light and ultraviolet light. For example, the conductive transparent electrode 403 is made of ITO (Indium Tin Oxide).

The photoelectric conversion film 404 converts light into signal charges. Specifically, the photoelectric conversion film 404 is formed under the conductive transparent electrode 403 and is composed of organic molecules having high light absorption ability. The organic molecules constituting the photoelectric conversion film 104 is made of, for example, fullerene C _60. The thickness of the photoelectric conversion film 404 is, for example, 500 nm. The photoelectric conversion film 404 is formed using, for example, a vacuum deposition method.

  The plurality of lower electrodes 406 are arranged in a matrix above the substrate 410. The plurality of lower electrodes 406 are electrically isolated from each other. Specifically, the lower electrode 406 is formed between the interelectrode insulating films 405 and collects holes generated in the photoelectric conversion film 404. The lower electrode 406 is made of, for example, TiN. The lower electrode 406 is formed over the planarized insulating film 407 with a thickness of 100 nm.

  Further, the lower electrodes 406 are separated at intervals of 0.2 μm. An interelectrode insulating film 405 is also embedded in this isolation region.

  Further, a power feeding layer 408 is disposed below the isolation region and below the insulating film 407. The power feeding layer 408 is made of Cu, for example. Specifically, the power feeding layer 408 is a region between the adjacent lower electrodes 406 and is formed between the lower electrode 406 and the substrate 410. In addition, a potential independent of the lower electrode 406 can be supplied to the power feeding layer 408. Specifically, a potential for discharging signal charges is supplied to the power supply layer 408 during an exposure operation in which the photoelectric conversion film 404 performs photoelectric conversion and in a read operation in which the signal read circuit 209 generates a read signal. . For example, when the signal charge is a hole, a positive voltage is applied. Thereby, it can prevent that a hole mixes into each pixel from an adjacent pixel. Such voltage application control is performed by, for example, a control unit (not shown) included in the solid-state imaging device 201.

  A wiring layer 409 is connected to the power feeding layer 408. The wiring layer 409 is connected to the gate terminals of the FD portion 302 and the amplification transistor 303. Further, the FD portion 302 is electrically connected to the source terminal of the reset transistor 304. Further, the source terminal of the reset transistor 304 and the FD portion 302 share a diffusion region. These transistors, a selection transistor 305 (not shown) formed in the same pixel, and the FD portion 302 are all formed in the same P-type well 411. The well 411 is formed on the substrate 410. That is, the signal readout circuit 209 shown in FIG. 2 is formed on the substrate 410, and by detecting a change in current or voltage generated in each of the plurality of lower electrodes 406, a readout signal corresponding to the signal charge is generated. Generate. In addition, the amplification transistor 303 generates a read signal by amplifying a change in current or voltage generated in the lower electrode 406.

Each transistor is electrically isolated by an STI region 412 made of SiO ₂ .

  FIG. 5 is a block diagram showing the configuration of the flame detection ultraviolet camera. The flame detection camera 501 includes a lens 502, an ultraviolet light receiving element 503, an analog front end 504, a signal processing unit 505, and a display unit 506. The analog front end 504 includes a CDS (Correlated Double Sampling) circuit 510, a PGA (Programmable Gain Amplifier) circuit 511, and an ADC (Analog-to-Digital Converter) circuit 512.

  The ultraviolet light collected by the lens 502 is converted into a signal by the ultraviolet light receiving element 503 and input to the analog front end 504. In the analog front end 504, the input signal is first suppressed in fixed pattern noise by the CDS circuit 510, then amplified by the PGA circuit 511, and finally converted into a digital signal by the ADC circuit 512, followed by signal processing. The image is processed by the unit 505 and created as an image by the display unit 506. The signal processing unit 505 may be provided with a circuit that performs, for example, frame addition averaging or pixel addition averaging in order to reduce random noise and increase S / N.

  FIG. 6A is an image photographed by a solid-state imaging device for visible light. As shown in FIG. 6A, in the color image, the flame emitted from the lighter is reflected. FIG. 6B is an image taken by the solid-state imaging device according to the present embodiment. As shown in FIG. 6B, in the ultraviolet light image, only the ultraviolet light emitted from the flame is detected and displayed.

(Embodiment 3)
A third embodiment will be described with reference to FIGS. Note that the block diagram of the solid-state imaging device 201 according to the third embodiment is the same as FIG. 2 shown in the second embodiment. In addition, the generation of the control signal shown below is performed by, for example, a control unit (not shown) included in the solid-state imaging device 201, as in the first embodiment.

  FIG. 7 is a block diagram illustrating an exemplary configuration of a solid-state imaging device 701 according to a modification. This solid-state imaging device 701 is configured by partially changing the pixel portion of the solid-state imaging device 201.

  In the pixel portion of the solid-state imaging device 701, pixels having filters each having a transmission region for RGB and ultraviolet light are arranged on the array. The arrangement of pixels having RGB and ultraviolet light transmission filters is not limited to this example, and this arrangement may be mixed with part of the Bayer arrangement.

  FIG. 8A is a block diagram illustrating a configuration of a flame detection camera. The solid-state imaging device 801 is configured by adding an analog front end 805 for detecting visible light, a signal processing unit 806, and a visible light display unit 807 to the solid-state imaging device 501. With such a configuration, it is possible to provide a solid-state imaging device that simultaneously detects and displays an image by ultraviolet light and visible light.

  Here, a comparator is provided in the ultraviolet light signal processing unit 505, and the signal output is compared with a predetermined reference level to determine whether or not it is larger than the reference level. A system is provided in which a trigger is given when the amount of ultraviolet light exceeds a certain threshold, and a signal is read from a pixel on which a visible light transmission filter is mounted. With this configuration, for example, it is possible to realize a single flame detection device or flame imaging device that outputs a captured color image only when ultraviolet light from a flame is sensed.

  Such a system can also be realized with a configuration of two imaging devices for ultraviolet light and visible light as shown in FIG. 8B. Although the cost and system size of the camera of FIG. 8B are larger than those of the camera of FIG. 8A, sensitivity to ultraviolet light and visible light can be increased.

  The solid-state imaging device according to the embodiment of the present disclosure has been described above, but the present disclosure is not limited to this embodiment. For example, the control circuit 407 can be controlled with a higher degree of freedom by a control signal from the outside of the chip.

  Each processing unit included in the solid-state imaging device according to the above-described embodiment is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  Further, the circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  In addition, in the above cross-sectional view, the corners and sides of each component are described linearly, but the present disclosure also includes those in which the corners and sides are rounded for manufacturing reasons.

  Moreover, you may combine at least one part among the functions of the solid-state imaging device which concerns on the said embodiment, and those modifications.

  Moreover, all the numbers used above are illustrated for specifically explaining the present disclosure, and the present disclosure is not limited to the illustrated numbers. In addition, logic levels represented by high / low or switching states represented by on / off are illustrative only for purposes of illustrating the present disclosure, and different combinations of illustrated logic levels or switching states. Therefore, it is possible to obtain an equivalent result. In addition, n-type and p-type transistors and the like are exemplified for specifically explaining the present disclosure, and it is possible to obtain equivalent results by inverting them. In addition, the materials of the constituent elements described above are all exemplified for specifically describing the present disclosure, and the present disclosure is not limited to the exemplified materials. In addition, the connection relationship between the components is exemplified for specifically explaining the present disclosure, and the connection relationship for realizing the functions of the present disclosure is not limited thereto.

  In the above description, an example using a MOS transistor is shown, but other transistors may be used.

  Further, various modifications in which the present embodiment is modified within the scope conceivable by those skilled in the art are included in the present disclosure without departing from the gist of the present disclosure.

  The present disclosure can be applied to an ultraviolet light detection apparatus. Further, the present disclosure can be applied to an automatic fire detection device, a fire monitoring system, a flame imaging device, and the like.

DESCRIPTION OF SYMBOLS 100 Ultraviolet light detection part 101 Ultraviolet light transmission filter 102 Protective film 103 Conductive transparent electrode 104 Photoelectric conversion film 106 Lower electrode 107 Charge storage part 108 Amplifier circuit part 109 Data storage part

Claims (12)

A first electrode;
A photoelectric conversion film disposed on the first electrode;
A transparent electrode disposed on the photoelectric conversion film;
An ultraviolet light transmission filter disposed on the transparent electrode,
The photoelectric conversion film has a maximum absorption coefficient in an ultraviolet light region, and the ultraviolet light transmission filter has a maximum transmittance in the ultraviolet light region. The photodetector according to claim 1, wherein the ultraviolet light transmission filter has the maximum transmittance in a wavelength range of 200 nm or more and 300 nm or less. The absorption coefficient of the photoelectric conversion film is
Having a first peak in the ultraviolet region;
The photodetector according to claim 1, wherein a second peak smaller than the first peak is included in a visible light region. The first peak is an absorption peak derived from a HOMO-LUMO gap,
The photodetector according to any one of claims 1 to 3, wherein the second peak is an absorption peak derived from an exciton peak. The photodetector according to any one of claims 1 to 4,
A readout circuit for reading out an output signal from the photodetector;
A control circuit that controls an output operation from the photodetector and a read operation of the read circuit;
The readout circuit and the control circuit are photodetection devices formed on the same substrate. A semiconductor substrate;
A plurality of first electrodes arranged in an array above the semiconductor substrate, each constituting a different unit pixel;
A photoelectric conversion film formed on the plurality of first electrodes;
A transparent electrode formed on the photoelectric conversion film;
A plurality of ultraviolet light transmission filters formed on the transparent electrode and corresponding to each of the plurality of first electrodes;
Charge storage formed in the semiconductor substrate corresponding to each of the plurality of first electrodes, electrically connected to the corresponding first electrode, and storing charges generated by photoelectric conversion in the photoelectric conversion film With areas,
At least some of the plurality of ultraviolet light transmission filters have a maximum transmittance in the ultraviolet light region,
The photoelectric conversion film has a maximum absorption coefficient in the ultraviolet light region. The solid-state imaging device according to claim 6, wherein the plurality of ultraviolet light transmission filters include a filter having a maximum transmittance in a visible light region. The solid-state imaging device according to claim 6, wherein the ultraviolet light transmission filter has the maximum transmittance in a wavelength range of 200 nm or more and 300 nm or less. The absorption coefficient of the photoelectric conversion film is
Having a first peak in the ultraviolet region;
Having a second peak in the visible region that is smaller than the first peak;
The solid-state imaging device according to claim 6, wherein the ultraviolet light transmission filter transmits light having a wavelength corresponding to the first peak. The first peak is an absorption peak derived from a HOMO-LUMO gap,
The solid-state imaging device according to claim 6, wherein the second peak is an absorption peak derived from an exciton peak. A solid-state imaging device according to any one of claims 6 to 10,
A camera system comprising image display means for displaying at least one of an ultraviolet image and a visible light image obtained from the solid-state imaging device. The camera system according to claim 11, which detects ultraviolet light generated from a flame at the time of a fire.

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