JP2013254840A - Solid state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both a wide dynamic range and high picture quality at low temperatures in a solid state image sensor.SOLUTION: In a solid state image sensor 1 including a plurality of pixels 5 arranged in two dimensional form, each of the plurality of pixels 5 include an on-substrate photoelectric conversion element 20 formed on the upper part of a semiconductor substrate and an intra-substrate photoelectric conversion element 13 formed inside the semiconductor substrate below the on-substrate photoelectric conversion element 20. The intra-substrate photoelectric conversion element 13 and the on-substrate photoelectric conversion element 20 in each pixel detect light having the same color and have mutually different photoelectric conversion sensitivities for incident light impinging upon the pixel. A distance in the lamination direction between the intra-substrate photoelectric conversion element 13 and the on-substrate photoelectric conversion element 20 in each pixel, d, is 1.5 μm to 4 μm, both ends inclusive.

Description

  The present invention relates to a solid-state imaging device including a photoelectric conversion unit that generates charges when irradiated with light, and relates to a solid-state imaging device with a wide dynamic range.

  As a solid-state imaging device, a single-plate CCD image sensor or CMOS in which a large number of light receiving parts (photodiodes) are integrated on the surface of a semiconductor substrate and R, G, B color filters are stacked on each light receiving part in recent years. The type image sensor has made significant progress, and at present, an image sensor in which millions of light receiving portions (pixels) are integrated on one chip is mounted on a digital camera.

  As miniaturization progresses, there is a problem that the number of electrons that can be accumulated per pixel is reduced in principle, resulting in a decrease in dynamic range. When the number of electrons exceeds the saturation level, overexposure, blackout, or the like occurs in the image. In order to solve this problem, Patent Document 1 discloses that a photoelectric conversion film that generates a charge by infrared (IR) absorption is disposed on a photoelectric conversion element in a substrate, and a voltage applied to the photoelectric conversion film is adjusted so that photoelectric conversion is performed. An imaging apparatus has been proposed in which no signal exceeding the saturation level exists in the signal from the conversion film. Furthermore, by providing a color filter between the photoelectric conversion film and the in-substrate photoelectric conversion element, color image data and infrared image data can be acquired by one imaging, and the signal from the in-substrate photoelectric conversion element is saturated. Even in this case, the object can be faithfully reproduced by complementing with the infrared pixel data.

  Patent Document 2 discloses a hybrid type image pickup device in which one pixel is composed of two or more photoelectric conversion elements having different photoelectric conversion sensitivities in order to achieve both a wide dynamic range and high image quality. Proposed.

  The configuration of including a plurality of photoelectric conversion elements for one pixel is also disclosed in Patent Document 3, but Patent Document 3 can simultaneously perform imaging of a recorded image and detection of a phase difference. In order to realize an image pickup device capable of performing auto-focusing on the whole, the first photoelectric conversion unit provided between the microlens and its focal point and a position overlapping the focal point of the microlens, And a second photoelectric conversion unit having a photoelectric conversion region in a direction deviated from the optical axis of the lens, and having a photoelectric conversion region in a direction deviated from the optical axis of the microlens. An image sensor composed of two pixel groups having the above is disclosed, which is irrelevant to the wide dynamic range.

JP 2009-49525 A JP 2007-201209 A JP 2011-103335 A

  According to the hybrid solid-state image sensor of Patent Document 2, the dynamic range can be expanded.

  However, studies by the present inventors have revealed a problem that in the configuration of the hybrid solid-state imaging device described in Patent Document 2, an afterimage may occur greatly at an operating environment temperature of 0 ° C. or lower. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device capable of realizing high-quality imaging while suppressing the influence of an afterimage even at a wide dynamic range and at low temperatures.

The solid-state imaging device of the present invention is a solid-state imaging device having a plurality of pixels arranged two-dimensionally,
Each of the plurality of pixels includes a substrate photoelectric conversion element formed above the semiconductor substrate, and a substrate photoelectric conversion element formed in the semiconductor substrate below the substrate photoelectric conversion element,
The in-substrate photoelectric conversion element and the on-substrate photoelectric conversion element in each pixel detect light of the same color and have different photoelectric conversion sensitivities with respect to incident light incident on the pixel,
In each pixel, the stacking direction distance between the in-substrate photoelectric conversion element and the on-substrate photoelectric conversion element is 1.5 μm or more and 4 μm or less.

  In the solid-state imaging device of the present invention, a photoelectric conversion element on a substrate is formed by laminating a pixel electrode, an organic photoelectric conversion film, and an upper electrode on the semiconductor substrate in this order, and the thickness of the pixel electrode is 10 nm or more and 100 nm or less. It is preferable that

  Further, the photoelectric conversion film can be an organic panchromatic film formed as a film common to a plurality of pixels, and a color filter can be provided on the photoelectric conversion element on the substrate.

  In the solid-state imaging device of the present invention, the on-substrate photoelectric conversion element and the in-substrate photoelectric conversion element only have to have different photoelectric conversion sensitivities, and any of them may be relatively high in sensitivity. It is desirable that the photoelectric conversion element has higher sensitivity than the in-substrate photoelectric conversion element.

  The thickness of the organic panchromatic film may be 50 nm or more and 1000 nm or less, and the absorption rate of incident light in the photoelectric conversion element on the substrate may be 50% or more. At this time, the on-substrate photoelectric conversion element can be made more sensitive than the in-substrate photoelectric conversion element.

  Alternatively, the thickness of the organic panchromatic film may be 2 nm or more and 200 nm or less, and the absorption rate of incident light in the photoelectric conversion element on the substrate may be less than 50%. At this time, the in-substrate photoelectric conversion element can be made more sensitive than the on-substrate photoelectric conversion element.

  According to the solid-state imaging device of the present invention, each pixel includes the on-substrate photoelectric conversion device and the in-substrate photoelectric conversion device, and the distance between both is 1.5 μm or more and 4 μm or less. Also, it is possible to achieve both high-quality image acquisition with little afterimage even at low temperatures of 0 ° C. or less.

1 is a schematic cross-sectional view showing a configuration of a solid-state imaging device according to a first embodiment of the present invention. 1 is a diagram showing a configuration of a signal readout circuit of a PD on a substrate of a solid-state imaging device according to an embodiment Explanatory drawing for demonstrating the broadening of the dynamic range in the solid-state image sensor of 1st Embodiment. Sectional schematic diagram which shows the structure of the solid-state image sensor which concerns on the 2nd Embodiment of this invention. Explanatory drawing for demonstrating the broadening of the dynamic range in the solid-state image sensor of 2nd Embodiment. Graph showing afterimage PD distance dependence Graph showing afterimage pixel electrode thickness dependence

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a part of an imaging unit of a solid-state imaging device 1 for explaining an embodiment of the present invention. The solid-state imaging device 1 has an imaging unit including a plurality of pixels arranged in a two-dimensional manner on a substrate surface.

  FIG. 1 shows an R pixel 5R that acquires red, a G pixel 5G that acquires green, and blue as three adjacent pixels 5 in the imaging unit as part of a cross section perpendicular to the substrate surface of the solid-state imaging device 1. B pixels 5B are shown respectively. In the following description, R, G, and B are added to the end of the reference numerals to indicate that each element is any element of R, G, and B pixels.

  The solid-state imaging device 1 includes a semiconductor substrate 10 in which a p-well layer 12 is formed on an n-type silicon substrate 11. The p-well layer 12 includes an embedded photodiode 13 (hereinafter referred to as an in-substrate photoelectric conversion element). And an n-type impurity diffusion region 14 and a signal readout circuit 15 are provided. One signal readout circuit 15 is provided for each substrate PD 13 and each impurity diffusion region 14.

  A transparent insulating film 16 is provided on the p-well layer 12. The insulating film 16 is provided with a plurality of pixel electrodes 21 embedded so as to form the same plane as the upper surface thereof. The pixel electrode 21 is made of an electrode material that is transparent to visible light, such as ITO.

  A columnar contact portion 18 extends in the thickness direction of the insulating film 16 in the insulating film 16. An upper end portion of the contact portion 18 is connected to each pixel electrode 21, and a lower end portion is connected to the impurity diffusion region 14 provided in the surface layer of the p-well layer 12 of the semiconductor substrate 10. The contact portion 18 may be subjected to an insulation process so as not to be electrically connected to other than the pixel electrode 21 and the impurity diffusion region 14. Examples of the insulation treatment include a configuration in which a slight gap is formed between the contact portion 18 and another conductive material, and the gap is filled with an insulating material.

Further, a light shielding film 17 made of a material such as tungsten having a light shielding property with respect to visible light is formed in the insulating film 16. The light shielding film 17 is opened above the PD 13 in the substrate. Since the impurity diffusion region 14 and the signal readout circuit 15 are covered with the light shielding film 17, the region other than the substrate PD 13 of the semiconductor substrate 10 is shielded from light.
In addition, a wiring layer (not shown) is formed in the insulating film 16. The light shielding film 17 may also serve as a wiring layer.

Further, a photoelectric conversion film 22 formed as a common film is provided on all the pixel electrodes so as to cover the upper surfaces of the insulating film 16 and the pixel electrodes 21. The photoelectric conversion film 22 may be either an organic material that absorbs incident light and generates an electric charge according to the absorbed light amount, or an inorganic material such as amorphous silicon.
In the present embodiment, the photoelectric conversion film 22 is a so-called panchromatic film having sensitivity over the entire visible light wavelength range. In particular, an organic panchromatic film is suitable.

On the photoelectric conversion film 22, a counter electrode 24 made of a similar common film is provided. Similar to the pixel electrode 21, the counter electrode 24 is made of an electrode material that is transparent to visible light, such as ITO.
A function such as a charge blocking layer that suppresses the injection of charge from the electrode to the photoelectric conversion film 22 between the photoelectric conversion film 22 and the counter electrode 24 or between the photoelectric conversion film 22 and the pixel electrode 21. A layer may be provided.

  The pixel electrode 21, the photoelectric conversion film 22, and the counter electrode 24 constitute a substrate photoelectric conversion element 20 (hereinafter referred to as a substrate PD 20). By applying a bias voltage between the pixel electrode 21 and the counter electrode 24, the signal charge generated in the photoelectric conversion film 22 can be moved to the pixel electrode 21 and collected.

  FIG. 2 shows the configuration of the signal readout circuit 15 that accumulates and reads out the charges generated in each PD. As shown in FIG. 2, the signal readout circuit 15 includes a floating diffusion FD (corresponding to an accumulation unit) (hereinafter simply referred to as FD), an output transistor 112, a reset transistor 113, and a selection transistor 114. . The output transistor 112, the reset transistor 113, and the selection transistor 114 are each composed of an n-channel MOS transistor. Hereinafter, the signal readout circuit 15 connected to the on-substrate PD 20 will be described as an example.

  In the PD 20 on the substrate of the present embodiment, a bias voltage is applied to the counter electrode 24 so that holes move to the pixel electrode 21 and electrons move to the counter electrode 24 among charges generated in the photoelectric conversion film 22. Applied.

  The FD is composed of an n-type impurity region electrically connected to the pixel electrode 21. Since the potential of the FD changes according to the amount of holes collected by the pixel electrode 21, the FD functions as a charge storage unit.

  The output transistor 112 converts the charge signal stored in the FD into a voltage signal and outputs it to the signal line. The gate terminal of the output transistor 112 is electrically connected to the FD, and the drain terminal is connected to the power supply voltage Vdd of the solid-state imaging device. The source terminal of the output transistor 112 is connected to the drain terminal of the selection transistor 114. The signal readout circuit in the present embodiment is a circuit having a so-called three-transistor configuration in which the FD, the pixel electrode 21 of the photoelectric conversion element 20, and the gate terminal of the output transistor 112 are directly connected.

  The reset transistor 113 resets the potential of the FD to a reference potential. The FD is electrically connected to the drain terminal of the reset transistor 113, the reset power supply is connected to the source terminal, and the voltage RD is supplied. When the reset pulse RS applied to the gate terminal of the reset transistor 113 becomes a high level, the reset transistor 113 is turned on, and electrons are injected from the source to the drain of the reset transistor 113. Then, due to the injection of electrons, the potential of the FD drops and the potential of the FD is reset to the reference potential. The selection transistor 114 has a source terminal connected to the signal line, and selectively outputs a signal output from the output transistor 112 of each pixel to a signal line provided for each column. . When the selection pulse RW applied to the gate terminal of the selection transistor 114 becomes a high level, the selection transistor 114 is turned on, whereby a signal output from the output transistor 112 of each pixel is output to the signal line.

  The signal readout circuit connected to the PD 13 in the substrate has the same configuration, but the signal charge to be read out can be selected as appropriate. For example, it is possible to obtain optimum signals such as reading a hole signal from the PD 20 on the substrate and reading an electronic signal from the PD 13 in the substrate.

  In the above description, the on-substrate PD is described as performing the hole collection type signal readout, but the on-substrate PD may also be performed as the electron collection type signal readout. However, the hole collection type is preferable because the storage capacity can be greatly increased.

  The in-substrate PD 13 and the on-substrate PD 20 are two-dimensionally arrayed by the number of pixels so as to correspond 1: 1. That is, each pixel 5 includes one in-substrate PD 13 and one on-substrate PD 20 disposed above the in-substrate PD 13.

  A protective film 26 is provided on the counter electrode 24, and a color filter layer 30 is disposed on the protective film 26. The color filter layer 30 includes an R color filter 31R that transmits red wavelength light, a G color filter 31G that transmits green wavelength light, and a B color filter 31B that transmits blue wavelength light, for example, in a Bayer array. It is arranged. The arrangement of the color filters 31R, 31G, and 31B in the color filter layer 30 is not limited to the Bayer arrangement. In addition to R, G, and B, a W (white) color filter may be provided.

Here, the two photoelectric conversion elements 13 and 20 in each pixel 5 are set to have different photoelectric conversion sensitivities with respect to incident light incident on each pixel.
Photoelectric conversion sensitivity (V / 1x / sec) is an index that indicates how much voltage is obtained from a signal that can be extracted from a photoelectric conversion element when a predetermined amount of light is incident. This is used as an index indicating a voltage obtained from a signal that can be extracted from the PD on the substrate and the PD in the substrate in the pixel with respect to the incident light to each pixel.

In the signal readout circuit shown in FIG. 2, by adjusting the power supply voltage Vdd or adjusting the capacitance accumulated in the FD to optimize the charge-voltage conversion gain (V / e ⁻ ), etc. The difference in sensitivity with PD can be adjusted.

  A high-sensitivity photoelectric conversion element can obtain a large number of signals with a small amount of light, so it is ideal for shooting subjects with low illuminance. However, when a large amount of light is incident, the signal is saturated. Therefore, it is not suitable for photographing a high-illuminance subject. On the other hand, a low-sensitivity photoelectric conversion element is optimal for shooting a high-illuminance subject because it cannot obtain a large number of signals even when a large amount of light is incident. The obtained signal is too small and is not suitable for photographing a low-illuminance subject.

  In the present invention, a sensitivity difference is given to the photoelectric conversion sensitivity with respect to the incident light of the PD 13 on the substrate and the PD 20 on the substrate, and the signal obtained from the relatively low sensitivity photoelectric conversion element and the signal obtained from the relatively high sensitivity photoelectric conversion element are obtained. By combining these signals, the dynamic range of the solid-state imaging device can be expanded.

Furthermore, the present invention is characterized in that the distance d between the in-substrate PD 13 and the on-substrate PD 20 is 1.5 μm or more and 4 μm or less. The distance d is a distance from the surface of the in-substrate PD 13 to the lower surface of the pixel electrode 21 of the on-substrate PD 20. When the distance is less than 1.5 μm, the distance between wiring layers (not shown) arranged in the insulating film 16 becomes close, and noise is generated between the wiring layers, leading to image degradation. Further, the present inventors have found that by setting the distance to 4 μm or less, the afterimage in a low temperature environment (approximately −45 ° C. to 0 ° C.) can be suppressed.
If the distance d between the PDs is not uniform, it is preferable that the distance is 1.5 μm or more and 4 μm or less regardless of the distance at any location.

  Further, the thickness te of the pixel electrode 21 is preferably 10 nm or more and 100 nm or less. By setting the thickness to 10 nm or more, the sheet resistance of the pixel electrode 21 can be sufficiently reduced, and an effect of further suppressing the occurrence of afterimages at low temperatures can be obtained. In order to reduce the sheet resistance, it is preferable that the thickness is large. On the other hand, if the thickness exceeds 100 nm, the unevenness of the pixel electrode and the contact with the photoelectric conversion film at the edge portion are not preferable.

  The photoelectric conversion element of the present invention comprises one on-substrate photoelectric conversion element and in-substrate photoelectric conversion element having different sensitivities that detect the same color in one pixel as described above, and the distance between the two is 1.5 μm or more, By setting the thickness to 4 μm or less, it is possible to achieve both a wide dynamic range and high-quality image acquisition at low temperatures.

  Hereinafter, an organic photoelectric conversion element (hereinafter referred to as OPD20) using an organic panchromatic material is provided as the PD 20 on the substrate, and a Si photoelectric conversion element (hereinafter referred to as SiPD13) is provided as the PD 13 in the substrate. A solid-state imaging device in which the sensitivity of the OPD 20 is higher than that of the SiPD 13 will be described.

As described above, the sensitivity between the in-substrate PD and the on-substrate PD is adjusted by adjusting the power supply voltage Vdd or adjusting the capacitance accumulated in the FD to optimize the charge voltage conversion gain (V / e ⁻ ). The difference is adjusted, and the sensitivity of the OPD 20 that is the PD on the substrate is set to be relatively higher than the sensitivity of the SiPD 13 that is the PD in the substrate. Sensitivity is set in consideration of the external quantum efficiencies of OPD 20 and SiPD 13.

  Then, in FIG. 1, the thickness of the photoelectric conversion film tp of the OPD 20 that is the PD on the substrate is set so that the incident light absorption rate is 50% or more in the range of about 50 nm to 1000 nm. In the OPD 20 with high sensitivity, if the absorption rate is small, the noise is increased. Therefore, the absorption rate of incident light in the OPD 20 with relatively high sensitivity is set to 50% or more.

The relationship between the absorptance and the thickness t _p in the photoelectric conversion layer 22 is not be said sweepingly because it depends on photoelectric conversion efficiency of the construction materials, depending on the desired absorption rate, taking into account the photoelectric conversion efficiency of the material Need to be set.

The wide dynamic range in the above configuration will be described with reference to FIG.
In FIG. 3, the horizontal axis represents the intensity of incident light to each pixel, the vertical axis represents the amount of signal with respect to the incident light, a represents the relationship between the amount of signal with respect to the incident light of OPD, and b represents the relationship with the amount of signal with respect to incident light of SiPD. Is shown. In FIG. 3, the larger the slope in the relationship of the signal amount with respect to the incident light, the higher the sensitivity. As shown in FIG. 3, the saturation signal amount of OPD can be made larger than the saturation signal amount of SiPD.

By making OPD highly sensitive and increasing the amount of incident light absorbed, it is advantageous in that there is little loss of light. The dynamic range of OPD is I _{o1 to} I _o2 , and the dynamic range of SiPD is I _{S1 to} I _S2 . By combining the two, a signal from a highly sensitive OPD is used in a region where the amount of incident light is small, and a signal from a low-sensitivity SiPD is used in a region where the amount of incident light is large, so that the dynamic range of this element is I _{o1 to} I _s2. Can be spread.

  In particular, as in this example, by using an organic photoelectric conversion film having an aperture ratio of 100% with respect to incident light as the photoelectric conversion film of the PD on the substrate, it is possible to achieve both a wide dynamic range and high sensitivity. As OPD is responsible for high-sensitivity imaging and SiPD is responsible for low-sensitivity imaging, most of the incident light is absorbed by the organic photoelectric conversion film, and only partially transmitted light is received by SiPD in the substrate. Even when intense light is incident, the charge generated in the SiPD can be suppressed to a small extent, so that the overexposure is suppressed, and at the same time, the organic photoelectric conversion film having a high aperture ratio appropriately receives even a small amount of light and maintains the gradation in the dark part. be able to. Since simultaneous shooting is performed with one pixel, the resolution can be maintained higher than that of a device including other pixels with different sensitivities, and the manufacturing is easy. In addition, in the case of a device that shoots by sensitivity with a time difference, it was difficult to shoot a movie, but with this configuration, high sensitivity and low sensitivity can be shot simultaneously, so that the video quality is also high. Shooting is possible.

  In addition, by using an organic panchromatic film for the photoelectric conversion film, fine coating and sensitivity variations for each pixel can be suppressed, and even in the case of ultra miniaturization, it is possible to stably manufacture with a high mass production yield.

  Next, a solid-state imaging device having the same configuration as described above, but the sensitivity of the OPD 20 is lower than that of the SiPD 13 will be described. FIG. 4 shows a cross-sectional view of a part of the solid-state imaging device of the design change example. In FIG. 4, the same components as those in FIG.

In the same manner as described above, the power supply voltage Vdd is adjusted, or the capacitance accumulated in the FD is adjusted to optimize the charge voltage conversion gain (V / e ⁻ ). And the sensitivity of the SiPD 13 that is the PD in the substrate is set to be relatively higher than the sensitivity of the OPD 20 that is the PD on the substrate. Sensitivity is set in consideration of the external quantum efficiencies of OPD 20 and SiPD 13.

  In this example, the thickness of the photoelectric conversion film tp of the OPD 20 is set in a range of about 2 nm to 200 nm so that the absorption rate of incident light is less than 50%. When the absorption rate of incident light in a high-sensitivity SiPD decreases, noise increases. Therefore, the absorption rate in the OPD 20 is less than 50% so that the absorption rate in the relatively high-sensitivity SiPD 13 is 50% or more. To suppress.

As in the above embodiment, the relationship between the absorptance and the thickness t _p in the photoelectric conversion layer 22 is not be said sweepingly because it depends on photoelectric conversion efficiency of the construction materials, depending on the desired absorptivity, structure It is necessary to set in consideration of the photoelectric conversion efficiency of the material.

The dynamic range widening in this case will be described with reference to FIG.
In FIG. 5, as in the case of the above embodiment, the on-substrate PD is provided with an organic panchromatic film in the photoelectric conversion film, and the in-substrate PD is SiPD. In FIG. 5, the horizontal axis represents the intensity of incident light to each pixel, the vertical axis represents the amount of signal with respect to the incident light, a represents the relationship between the amount of signal with respect to the incident light of OPD, and b represents the relationship with the amount of signal with respect to incident light of SiPD. Is shown. In FIG. 5, the larger the slope in the relationship of the signal amount with respect to the incident light, the higher the sensitivity. As shown in FIG. 5, the saturation signal amount of OPD can be made larger than the saturation signal amount of SiPD.

In this example, the dynamic range of OPD is I _{o1 to} I _o2 , and the dynamic range of SiPD is I _{S1 to} I _S2 . By combining both, using a signal from a high-sensitivity SiPD in a region where the amount of incident light is small, and using a signal from a low-sensitivity OPD in a region where the amount of incident light is large, the dynamic range of this element is I _{S1 to} I _o2 Can be spread. By making the sensitivity of the OPD having a larger saturation signal amount than SiPD low, the dynamic range can be expanded to a region where the incident light intensity is higher.

  The OPD 20 and its signal readout circuit 15 can increase the storage capacity by adopting a hole readout system that reads holes from the pixel electrode as shown in FIG. Therefore, by using OPD as a low sensitivity layer, the dynamic lens on the highlight side can be greatly expanded. By making the film thickness of the organic photoelectric conversion film ultra-thin, the organic photoelectric conversion film absorbs only a part of the incident light, and low-sensitivity photographing on the highlight side is performed. On the other hand, the light transmitted through the OPD 20 is received by the SiPD 13 installed in the substrate. While high-sensitivity shooting is performed by the high photoelectric conversion efficiency of the original Si photodiode, in the scene where the amount of light is large, the size of the storage capacity of the organic photoelectric conversion film is used to perform shooting with an unprecedented wide dynamic range. Can be realized.

  In the above description, the storage capacity of the OPD is described as being larger than the storage capacity of the SiPD. However, in each embodiment, even if the storage capacity of the OPD is not necessarily larger than the SiPD, if the sensitivity of the two is different, Compared to the case of a single PD, it is possible to obtain a wide dynamic effect. On the other hand, when the OPD has a relatively low sensitivity as described above, a wider dynamic can be achieved by sufficiently increasing the storage capacity of the OPD.

  Further, when the color filter layer does not include a plurality of color filters, and all the pixels are composed of a single color filter that receives only the same color (for example, G), a solid-state imaging device capable of only monochrome imaging It is possible to expand the dynamic range.

  In the solid-state imaging device described above, in one pixel, the area (light receiving area) of the in-substrate photoelectric conversion element 13 in plan view is equal to the area of the light receiving region of the on-substrate photoelectric conversion element 20 in plan view. On the other hand, if it is 20% or more and 90% lower, shading can be effectively reduced. A more preferable range is 40% to 90%, more preferably 50% to 80%, and more preferably 60% to 80%. Shading refers to a phenomenon in which imaging performance differs greatly between the peripheral part and the central part of a solid-state imaging device. The above range is preferable because shading when the area ratio is small may result in different sensitivity performance during low-illuminance photography, and when the area ratio is too large, color blur may occur. .

  In addition, in this pixel, in one pixel, the shift between the center of the light receiving region of the in-substrate photoelectric conversion element 13 in plan view and the center of the light receiving region of the on-substrate photoelectric conversion element 20 in plan view is If the width in the row direction or the column direction of the light receiving region of the photoelectric conversion element 20 is 30% or less, it is further suppressed, more preferably 20% or less, more preferably 10% or less, and most preferably the center coincides. This is the case.

  The solid-state imaging device of the present invention can be used in imaging devices such as digital cameras and digital video cameras. Further, it can be used by being mounted on an imaging module such as an electronic endoscope and a mobile phone.

Examples of the present invention and comparative examples will be described below.
An imaging device having the configuration shown in FIG. 1 was formed and evaluated.

  An OPD 20 comprising a pixel electrode ITO21 / electron blocking layer / photoelectric conversion layer 22 / upper electrode 24 is formed on a Si substrate on which the SiPD 13 and the signal readout circuit 15 are formed and the light shielding film 17, the wiring layer, and the interlayer insulating film 16 are formed. Formed. The pixel electrode ITO21 was formed with a thickness te = 50 nm. On the pixel electrode 21, as an electron blocking layer, the organic compound shown with the following compound 1 was formed with the film thickness of 100 nm by the vacuum evaporation method. Note that the electron blocking layer is not shown in FIG. On this electron blocking layer, a mixed layer of an organic compound represented by the following compound 2 and C60 (compound 2: C60 = 1: 2 (volume ratio)) is co-evaporated in vacuum with a film thickness of tp = 400 nm. Thus, the photoelectric conversion layer 22 in which the compound 2 and fullerene (C60) formed a bulk heterostructure was formed. The vapor deposition of the organic compounds was performed at a vacuum degree of 5.0 × 10 −4 Pa or less and a deposition rate of 1 Å / s to 10 Å / s. ITO was formed as a top electrode 24 on the photoelectric conversion layer 22 with a film thickness of 10 nm by high frequency magnetron sputtering.

  Further, a laminated film of aluminum oxide and silicon nitride was formed as a protective film 26 on the upper electrode 24. Aluminum oxide was formed to a thickness of 200 nm using an atomic layer deposition apparatus. Silicon nitride was formed to a thickness of 100 nm by magnetron sputtering. Further, an RGB color filter layer 30 was provided on the protective film 26.

  Here, an element in which the distance d between the PDs was changed by adjusting the thicknesses of the insulating film 16, the light shielding film 17, and the wiring layer (not shown) was prepared as an example and a comparative example of the present invention. Each element having a PD distance d of 1.4 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 4.0 μm, 5.0 μm, and 6.0 μm was fabricated.

  The device thus fabricated was irradiated with light of 500 lux / F4 at low temperature (0 ° C) every second by the shutter opening / closing operation, and the output signal immediately after the shutter was released (1/60 second) is the shutter. The percentage of the output signal at the time of opening was measured, and the average of 10 times was defined as an afterimage. When the afterimage was 1% or less, it was evaluated as good (G), and when the afterimage was more than 1%, it was evaluated as defective (NG). The results are shown in Table 1.

  The results of Table 1 are shown in FIG. In FIG. 6, the horizontal axis is the distance d between PDs, and the vertical axis is the afterimage (%). As shown in FIG. 6, it is apparent that the afterimage can be suppressed to 1% or less when the distance between PDs is in the range of 1.5 μm to 4.0 μm. In this example, the afterimage could be suppressed most at a distance between PDs of 2.5 μm to 3.0 μm.

  Next, in the above, the after-image is changed in the same manner as described above while the distance d between the PDs is fixed to 3.0 μm and the thickness te of the pixel electrode is changed to 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, 75 nm, 100 nm, 125 nm, and 150 nm. Asked. The results are shown in Table 2.

  The results of Table 2 are shown in FIG. In FIG. 7, the horizontal axis represents the pixel electrode thickness te, and the vertical axis represents the afterimage (%). As shown in FIG. 7, the afterimage was the smallest when the thickness of the pixel electrode was 30 nm, and the afterimage became larger as the thickness increased thereafter. On the other hand, afterimages increased as the thickness became thinner than 30 nm. When the thickness is in the range of 10 nm to 100 nm, the afterimage can be suppressed to 0.8% or less, which is preferable. In particular, the range of 20 nm to 50 nm is more preferable because the afterimage is 0.6% or less.

DESCRIPTION OF SYMBOLS 1 Solid-state image sensor 5 Pixel 10 Semiconductor substrate 13 Photoelectric conversion element 16 in a substrate Insulating layer 20 Photoelectric conversion element 21 on a substrate Pixel electrode 22 Photoelectric conversion film 24 Counter electrode 30 Color filter layer 31 Color filter

Claims (5)

A solid-state imaging device having a plurality of pixels arranged two-dimensionally,
Each of the plurality of pixels includes a substrate photoelectric conversion element formed above the semiconductor substrate, and a substrate photoelectric conversion element formed in the semiconductor substrate below the substrate photoelectric conversion element,
The in-substrate photoelectric conversion element and the on-substrate photoelectric conversion element in each pixel detect light of the same color and have different photoelectric conversion sensitivities for incident light incident on the pixel. And
A solid-state imaging device, wherein a distance in a stacking direction between the in-substrate photoelectric conversion device and the on-substrate photoelectric conversion device is 1.5 μm or more and 4 μm or less in each pixel. The photoelectric conversion element on the substrate is formed by laminating a pixel electrode, an organic photoelectric conversion film, and an upper electrode in this order on the semiconductor substrate,
The solid-state imaging device according to claim 1, wherein the pixel electrode has a thickness of 10 nm to 100 nm. The photoelectric conversion film is an organic panchromatic film formed as a film common to the plurality of pixels,
The solid-state imaging device according to claim 1, further comprising a color filter on the photoelectric conversion element on the substrate.   4. The solid-state imaging device according to claim 3, wherein the organic panchromatic film has a thickness of 50 nm or more and 1000 nm or less, and an absorptance of the incident light in the photoelectric conversion element on the substrate is 50% or more.   4. The solid-state imaging device according to claim 3, wherein the organic panchromatic film has a thickness of 2 nm or more and 200 nm or less, and an absorptance of the incident light in the photoelectric conversion device on the substrate is less than 50%.