JP2005303273A - Photoelectric conversion film stacked solid-state image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion film stacked solid-state image sensor, from which photoelectric charges can be extracted efficiently. <P>SOLUTION: The photoelectric conversion film stacked solid-state image sensor has a photoelectric conversion film 23 formed on a semiconductor substrate having a signal readout circuit. An incident light is photoelectrically converted to a signal according to the incident light quantity by the photoelectric conversion film 23, and is read out by the signal readout circuit. The photoelectric conversion film 23 is composed of deposition layers. The deposition layers comprises a first deposition layer 51, in which p-conductive quantum dots 55 and i-conductive quantum dots 56 are mixed, and a second deposition layer 52, in which n-conductive quantum dots 57 and i-conductive quantum dots 56 are mixed. A third deposition layer 53 consisting of i-conductive quantum dots 56 is preferably provided between the first deposition layer 51 and the second deposition layer 52. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion film stacked solid-state imaging device configured by stacking a photoelectric conversion film on a semiconductor substrate on which a signal readout circuit is formed.

  As a prototype element of the photoelectric conversion film laminated solid-state imaging device, for example, there is one described in Patent Document 1 below. In this solid-state imaging device, three photosensitive layers are stacked on a semiconductor substrate, and red (R), green (G), and blue (B) electrical signals detected in each photosensitive layer are transmitted to the surface of the semiconductor substrate. Reading is performed by the MOS circuit formed in the circuit.

  A solid-state imaging device having such a configuration has been proposed in the past. Thereafter, a large number of light receiving portions (photodiodes) are integrated on the surface portion of the semiconductor substrate, and red (R), green (G), and blue are integrated on each light receiving portion. The CCD type image sensor and CMOS type image sensor in which the color filters of each color (B) are laminated have advanced remarkably, and now, an image sensor in which millions of light receiving parts (pixels) are integrated on one chip is used as a digital still camera. It comes to be installed.

  However, the CCD type image sensor and the CMOS type image sensor have progressed to their limits, and the aperture size of one light receiving part is about 2 μm, which is close to the wavelength order of incident light, and the manufacturing yield is poor. Faced with the problem.

  In addition, the upper limit of the amount of photocharge accumulated in one miniaturized light receiving portion is as small as about 3000 electrons, which makes it difficult to express 256 gradations neatly. For this reason, it is difficult to expect an image sensor more than the current type in the CCD type or the CMOS type in terms of image quality and sensitivity.

  Therefore, as a solid-state imaging device that solves these problems, the solid-state imaging device proposed in Patent Document 1 has attracted attention, and image sensors described in Patent Document 2 and Patent Document 3 are newly proposed. It is becoming like this.

  In the image sensor described in Patent Document 2, ultrafine particles of silicon are dispersed in a medium to form a photoelectric conversion layer, and a plurality of photoelectric conversion layers having different ultrafine particle sizes are stacked on a semiconductor substrate. In each photoelectric conversion layer, electrical signals corresponding to the received light amounts of red, green and blue are generated.

  The same applies to the image sensor described in Patent Document 3, in which three nanosilicon layers having different particle diameters are stacked on a semiconductor substrate, and red, green, and blue electrical signals detected by each nanosilicon layer are detected. Is read out to the storage diode formed on the surface portion of the semiconductor substrate.

JP 58-103165 A Japanese Patent No. 3405099 Japanese Patent Laid-Open No. 2002-83946

  When silicon is used as the ultrafine particles used in the photoelectric conversion layer, the electron-hole pairs generated by receiving light are recombined in a short time on the surface of the ultrafine particles, and the charge is extracted before recombination. Therefore, there is a problem that the performance as a solid-state imaging device is not sufficient.

  In order to put the photoelectric conversion film laminated solid-state imaging device into practical use, it is necessary to solve the problem of what material and in what structure the photoelectric conversion film is formed.

  An object of the present invention is to provide a photoelectric conversion film stacked solid-state imaging device capable of efficiently taking out photoelectric charges from a photoelectric conversion film.

  The photoelectric conversion film stack type solid-state imaging device of the present invention has a photoelectric conversion film stacked on a semiconductor substrate on which a signal readout circuit is formed, and a signal corresponding to the amount of incident light photoelectrically converted by the photoelectric conversion film is the signal readout. In a photoelectric conversion film laminated solid-state imaging device that is read out to the outside by a circuit, the photoelectric conversion film is composed of a quantum dot deposition layer, and the deposition layer includes a p-type conductivity quantum dot and an i-type conductivity quantum dot. And a second deposition layer in which an n-type conductive quantum dot and the i-type conductive quantum dot are mixed.

  With this configuration, the photoelectric conversion film becomes a macroscopic pn junction and a potential gradient is formed in the photoelectric conversion film, so that it is easy to take out the photocharge generated by light incidence.

  The photoelectric conversion film laminated solid-state imaging device according to the present invention does not include the p-type conductive quantum dots and the n-type conductive quantum dots between the first deposited layer and the second deposited layer. A third deposited layer is formed by a type conductive quantum dot.

  With this configuration, the photoelectric conversion film becomes a pin junction macroscopically, and it becomes easier to take out the photocharge generated by light incidence by the potential gradient formed in the i layer.

  In the photoelectric conversion film stacked solid-state imaging device of the present invention, each of the quantum dots has a semiconductor ultrafine particle as a core, and the core is covered with a material having a larger optical band gap energy than the semiconductor ultrafine particle. And

  With this configuration, recombination on the surface of the ultrafine particles of electron-hole pairs generated when light is incident on the semiconductor ultrafine particles is suppressed, and the photocharge can be more easily taken out.

  The semiconductor ultrafine particle of the photoelectric conversion film laminated solid-state imaging device of the present invention is CdSe, and the material covering the CdSe is ZnS.

  This configuration facilitates the manufacture of the photoelectric conversion film.

  In the photoelectric conversion film stacked solid-state imaging device of the present invention, the semiconductor ultrafine particles are ZnTe, and the material covering the ZnTe is ZnS.

  This configuration facilitates the manufacture of the photoelectric conversion film.

  In the photoelectric conversion film laminated solid-state imaging device of the present invention, the semiconductor ultrafine particles are InN, and the material covering the InN is GaN.

  This configuration also facilitates the production of the photoelectric conversion film.

  The photoelectric conversion film laminated solid-state imaging device of the present invention is characterized in that the photoelectric conversion film sandwiched between two transparent electrode films is laminated in three layers via a transparent insulating film.

  With this configuration, a color image can be captured.

  In the photoelectric conversion film stacked solid-state imaging device of the present invention, among the three layers of photoelectric conversion films, the maximum value of light absorption of the photoelectric conversion film of the first layer is a wavelength of 420 to 500 nm, the second layer The photoelectric conversion film is provided in each photoelectric conversion film so that the maximum value of light absorption of the photoelectric conversion film is a wavelength of 500 to 580 nm, and the maximum value of light absorption of the photoelectric conversion film of the third layer is a wavelength of 580 to 660 nm. The average particle size of the quantum dots is determined.

  With this configuration, it is possible to extract image data divided into three primary colors of red (R), green (G), and blue (B).

  The photoelectric conversion film laminated solid-state imaging device of the present invention is characterized in that the photoelectric conversion film sandwiched between two transparent electrode films is stacked in four layers via a transparent insulating film.

  With this configuration, various signal processing is possible, and a color image with good color reproducibility can be captured.

  In the photoelectric conversion film stacked solid-state imaging device of the present invention, the maximum value of light absorption of the first photoelectric conversion film among the four photoelectric conversion films is a wavelength of 420 to 480 nm, the second layer. The maximum value of light absorption of the photoelectric conversion film is a wavelength of 480 to 520 nm, the maximum value of light absorption of the photoelectric conversion film of the third layer is a wavelength of 520 to 580 nm, and the maximum value of the photoelectric conversion film of the fourth layer is The average particle diameter of the quantum dots provided in each photoelectric conversion film is determined so that the maximum value of light absorption is a wavelength of 580 to 660 nm.

  With this configuration, it is possible to reproduce a color image according to human visibility.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the photoelectric conversion film laminated | stacked solid-state image sensor which can take out photoelectric charge (signal charge) from a photoelectric conversion film efficiently.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of one pixel of a photoelectric conversion film stacked solid-state imaging device according to an embodiment of the present invention. In this embodiment, three layers of photoelectric conversion films are stacked to extract an electrical signal corresponding to the three primary colors of red (R), green (G), and blue (B), that is, a configuration for capturing a color image. However, only one layer of the photoelectric conversion film may be provided to capture a monochrome image, for example, a monochrome image.

  In FIG. 1, on the surface portion of a P well layer 1 formed on an n-type silicon substrate 50, a high-concentration impurity region 2 for red signal storage, a MOS circuit 3 for reading red signals, and a green signal storage A high concentration impurity region 4, a green signal readout MOS circuit 5, a blue signal storage high concentration impurity region 6, and a blue signal readout MOS circuit 7 are formed.

  Each MOS circuit 3, 5, 7 is composed of a source and drain impurity region formed on the surface of the semiconductor substrate and a gate electrode formed via a gate insulating film 8. An insulating film 9 is laminated and planarized on the gate insulating film 8 and the gate electrode. In some cases, a light shielding film is formed on the surface of the insulating film 9, but when the light shielding film is formed, an insulating film 10 is further laminated so as to insulate the light shielding film. This is because the light shielding film is often formed of a metal thin film. When the light shielding film is not provided at this location, the illustrated insulating films 9 and 10 may be integrated.

  The signal charges stored in the high-concentration impurity regions 2, 4 and 6 for storing color signals described above are read out by the MOS circuits 3, 5 and 7, and further, although not shown, they are formed on the semiconductor substrate. Although it is taken out by the readout electrode, its configuration is the same as that of a conventional CMOS image sensor.

  In this example, the signal charge is read out by the MOS circuit formed on the semiconductor substrate. However, the charge stored in the high-concentration impurity regions 2, 4 and 6 for storing color signals is the same as that in the conventional CCD image sensor. Further, it is also possible to adopt a configuration in which it is moved along the vertical transfer path and read out along the horizontal transfer path.

  The above configuration is manufactured by a conventional CCD image sensor or CMOS image sensor semiconductor process, and a photoelectric conversion film stacked solid-state imaging device is manufactured by adding the configuration described below.

  A transparent electrode film 11 is formed on the insulating film 10 shown in FIG. The transparent electrode film 11 is electrically connected to the high concentration impurity region 2 for red signal accumulation by the electrode 12. This electrode 12 is electrically insulated from areas other than the transparent electrode film 11 and the high concentration impurity region 2. Then, a red detection photoelectric conversion film 13 is formed on the transparent electrode film 11, and a transparent electrode film 14 is further formed on the photoelectric conversion film 13. That is, the photoelectric conversion film 13 is sandwiched between the pair of transparent electrode films 11 and 14. Note that the electrode film 11 as the lowermost layer may be made opaque so that it also serves as a light shielding film.

  A transparent insulating film 15 is formed on the transparent electrode film 14, and a transparent electrode film 16 is formed on the transparent insulating film 15. The transparent electrode film 16 is electrically connected to the high-concentration impurity region 4 for storing the green signal by the electrode 17. This electrode 17 is electrically insulated from areas other than the transparent electrode film 16 and the high concentration impurity region 4. A green color detection photoelectric conversion film 18 is formed on the transparent electrode film 16, and a transparent electrode film 19 is formed on the photoelectric conversion film 18. That is, the photoelectric conversion film 18 is sandwiched between the pair of transparent electrode films 16 and 19.

  A transparent insulating film 20 is formed on the transparent electrode film 19, and a transparent electrode film 21 is formed on the transparent insulating film 20. The transparent electrode film 21 is electrically connected to the high concentration impurity region 6 for storing the blue signal by the electrode 22. This electrode 22 is electrically insulated from areas other than the transparent electrode film 21 and the high concentration impurity region 6. A blue color photoelectric conversion film 23 is formed on the transparent electrode film 21, and a transparent electrode film 24 is formed on the photoelectric conversion film 23. That is, the photoelectric conversion film 23 is sandwiched between the pair of transparent electrode films 21 and 24.

A transparent insulating film 25 is provided as the uppermost layer. In this embodiment, a light shielding film 26 for limiting the incident range of incident light to the pixel is provided in the transparent insulating film 25. The reason why the light shielding film 26 is provided in the uppermost layer in this embodiment is to further reduce the color mixture between pixels. As the homogeneous transparent electrode film, tin oxide (SnO ₂ ), titanium oxide (TiO ₂ ), indium oxide (InO ₂ ), and indium oxide-tin (ITO) thin film are used, but the present invention is not limited thereto. Examples of the formation method include a laser ablation method and a sputtering method.

  The structures of the photoelectric conversion films 23, 18 and 13 are basically the same, but the particle diameters of CdSe quantum dots provided in the films are different. The CdSe quantum dot in the blue color photoelectric conversion film 23 has the smallest particle size, then the CdSe quantum dot in the green color detection photoelectric conversion film 18 has an intermediate particle size, and the red color detection photoelectric conversion. The particle size of the CdSe quantum dots in the film 13 is the largest, and in any case, the particle size is on the order of nanometers.

  For example, the average particle diameter of CdSe quantum dots for blue detection is in the range of 1.7 to 2.5 nm, the average particle diameter of CdSe quantum dots for green detection is in the range of 2.5 to 4 nm, and the CdSe quantum for red detection The average particle size of the dots is preferably about 4 to 8 nm.

  These particle sizes are selected so that light absorption at the corresponding wavelength is increased and a large number of electron-hole pairs are generated. That is, the red detection is performed so that the maximum value of light absorption is 420 to 500 nm in the photoelectric conversion film 23 for blue detection, and the maximum value of light absorption is 500 to 580 nm in the photoelectric conversion film 18 for green detection. In the photoelectric conversion film 13 for use, the particle size is selected to be 580 to 660 nm.

  The embodiment shown in FIG. 1 is an example of a photoelectric conversion film stacked solid-state imaging device that detects three primary colors of red, green, and blue. However, a configuration that can detect four colors is also possible. FIG. 2 is a schematic cross-sectional view of one pixel of a photoelectric conversion film stacked solid-state imaging device that detects four colors, and is an intermediate color (GB: emerald) of green (G) and blue (B) with respect to the configuration of FIG. A layer in which a photoelectric conversion film 31 for detecting color) is sandwiched between transparent electrodes 32 and 33 is provided between a green detection layer and a blue detection layer. That is, the photoelectric conversion films 23, 31, 18, and 13 are provided in order from the top in ascending order of the wavelength of light to be detected.

  In this example, the maximum value of light absorption in the photoelectric conversion film 23 is 420 to 480 nm, the maximum value of light absorption in the photoelectric conversion film 31 is 480 to 520 nm, the maximum value of light absorption in the photoelectric conversion film 18 is 520 to 580 nm, The particle size of the quantum dots is determined so that the maximum value of light absorption in the conversion film 13 is 580 to 660 nm.

  Then, a high-concentration impurity region 36 for storing signal charges of intermediate colors is formed in the semiconductor substrate, and an electrode 35 electrically connected to the high-concentration impurity region 36 and the transparent electrode 32 and electrically insulated from other components is provided. A MOS circuit 37 for reading signal charges in the high concentration impurity region 36 is provided on the semiconductor substrate. Naturally, the transparent insulating film 34 is provided between the transparent electrode film 33 and the upper transparent electrode film 21.

  The advantage of detecting an intermediate color having a wavelength of 480 to 520 nm is to correct red according to human visibility. As shown in FIG. 3 as α, β, and γ, human visual sensitivity is negative in green (G), red (R), and blue (B). For this reason, even if color reproduction is performed by detecting only positive sensitivities of R, G, and B with a solid-state imaging device, an image seen by humans cannot be reproduced. Therefore, a signal processing in which β having the highest negative sensitivity, that is, negative red sensitivity is detected by the photoelectric conversion film 31 and this negative sensitivity is subtracted from the red sensitivity detected by the photoelectric conversion film 13 is disclosed in Japanese Patent No. 2872759. By performing the same signal processing as described, it is possible to reproduce human sensitivity to red.

  FIG. 4 is a circuit diagram of the MOS circuits 3, 5, and 7 shown in FIG. This MOS circuit is composed of three FET elements for each of R, G, and B, and the circuit configuration is the same as the circuit used in a conventional CMOS image sensor. In the solid-state imaging device of FIG. 2, only three FET elements for intermediate colors (GB) are added for one pixel.

  In the conventional CMOS type image sensor, it is necessary to provide a “light-receiving part” on the semiconductor surface. Therefore, when manufacturing these MOS circuits on the semiconductor surface, the light-receiving part must be manufactured in a narrow place because of the widening of the light-receiving part. It was. However, in the photoelectric conversion film laminated solid-state imaging device of the present embodiment, it is not necessary to provide a “light receiving portion” on the semiconductor surface, so that the MOS circuit can be easily manufactured. In addition, since there is room in the wiring space, in FIG. 4, one of R, G, and B is sequentially read while being selected by a select signal, but the wiring connection is such that R, G, and B can be read together. It becomes easy. This is the same even if the readout circuit is not a MOS circuit but a type in which a charge transfer path is provided like a CCD image sensor.

  The structure shown in FIGS. 1 and 2 is for one pixel, but these pixels are provided in an array in the vertical and horizontal directions on the surface side of the semiconductor substrate. However, it is not necessary to divide and stack the photoelectric conversion films according to each pixel, and the photoelectric conversion films can be stacked in a single structure on the entire surface of the semiconductor substrate. One pixel and one pixel can be separated by forming one of the pair of transparent electrodes sandwiching each photoelectric conversion film into one pixel and one pixel.

  When light from a subject is incident on the photoelectric conversion film stacked solid-state imaging device of FIG. 1 or 2 described above, blue light of the incident light is absorbed by the photoelectric conversion film 23 and green light is converted into a photoelectric conversion film. The red light is absorbed by the photoelectric conversion film 13. In the case of FIG. 2, emerald light that is an intermediate color (GB) of blue and green is absorbed by the photoelectric conversion film 31.

  The quantum dots (ultrafine particles) constituting the photoelectric conversion film 23 absorb incident light and generate electron-hole pairs. This electron-hole pair recombines with time and emits blue light. However, when a voltage is applied between the transparent electrodes 24 and 21, before the electrons are recombined, It flows from the transparent electrode 21 through the electrode 22 to the high concentration impurity region 6.

  Similarly, electrons corresponding to the green incident light amount generated in the photoelectric conversion film 18 flow into the high concentration impurity region 4, and electrons corresponding to the red incident light amount generated in the photoelectric conversion film 13 are in the high concentration impurity region. 2, electrons corresponding to the amount of incident light of the emerald color flow to the high concentration impurity region 36 (FIG. 2). Then, by the MOS circuits 3, 5, 7, and 37, electrons having a charge amount corresponding to each color are read out to the outside.

  FIG. 5 is a schematic cross-sectional view of the photoelectric conversion films 23, 18, 13, and 31. In the illustrated example, the photoelectric conversion film 23 provided between the transparent electrode films 24 and 21 (18, 13, and 31 is the same, and only the particle diameter of the quantum dots is different) is on the electrode 24 side. It consists of a p-layer region 51, an n-layer region 52 on the electrode 21 side, and an i-layer region 53 provided therebetween.

  The p-layer region 51 has p-type quantum dots 55 coated with ZnS and coated with ZnS, and i-type coated with ZnS and coated with ZnS. It consists of a layer in which conductive quantum dots 56 are mixed at a predetermined ratio.

  The i-layer region 53 is a layer in which i-type conductive quantum dots 56 in which i-type conductive CdSe ultrafine particles are used as a core and coated with ZnS are deposited.

  The n-layer region 52 has n-type conductive CdSe ultrafine particles as a core, n-type conductive quantum dots 57 coated with ZnS, and i-type conductive CdSe ultrafine particles as a core, and this is coated with ZnS. The i-type conductive quantum dots 56 are mixed at a predetermined ratio.

  FIG. 6 is a schematic diagram of an ideal energy band assumed from the configuration shown in FIG. Since the CdSe quantum dots inside the ultrafine particles are adjacent to each other at a very close distance across the outer shell ZnS, the discontinuous levels in the CdSe particles caused by the quantum confinement effect are the discontinuous levels in the adjacent CdSe particles. Interacts with the position to produce a miniband.

  The diffusion potential of the junction of the p-type layer 51-i-type layer 53-n-type layer 52 of the photoelectric conversion film 23 (this is called a macroscopic pin junction) and the reverse bias voltage applied from the external power source. In the i-layer region 53 where the potential gradient is generated, electrons and holes generated in the CdSe particles by light irradiation are separated by charge through a miniband.

  In order to form a miniband, the distance between adjacent CdSe quantum dot surfaces (the sum of the thicknesses of the ZnS coating layer and the organic molecular layer separating the CdSe quantum dots) may be in the range of 0.3 nm to 5 nm. Preferably, it is in the range of 0.3 nm to 2 nm. As the interparticle distance increases, the electrical conductivity at the time of generation of carriers due to light irradiation decreases significantly, so that a larger reverse bias voltage is required, leading to an increase in noise.

  In the above-described embodiment, the pin junction is macroscopically. However, the potential gradient can be generated by omitting the i-layer region 53 and macroscopically forming the pn junction. . However, the potential gradient can be controlled by interposing the i layer region 53 between the p layer region 51 and the n layer region 53, which is more preferable.

  The production of CdSe ultrafine particles is described in detail in, for example, “Journal of American Chemical Society” (BODabbousiefaAJoumalofAmencanChemicalSociety, Vo1115, 8706-8715 (1993)). It is described in detail in “Journal of Physical Chemistry” (CBMurray et al Journal of Physical Chemistry, Vol. L01, 9463-9475 (1997)).

For example, a solution of dimethylcadmium dissolved in trioctylphosphine (TOP) and a solution of trioctylphosphine selenide (TOPSe) dissolved in TOP are mixed and heated to about 300 ° C. in trioctylphosphine oxide (TOPO). inject.
Thereafter, the particle size of the ultrafine CdSe particles is controlled by adjusting the heating time and temperature, and the particle size is further classified by adding the extracted solution to methanol and centrifuging.

  After classifying the particle size, a solution redispersed in hexane is added to a solution composed of TOPO and TOP, heated, a solution in which diethyl zinc is dissolved in TOP, and a solution in which hexamethyldisilathian is dissolved in TOP are added, CdSe / ZnS is generated.

  Here, the temperature and addition amount are adjusted according to the particle diameter of the ultrafine CdSe particles and the thickness of the target ZnS coating. The resulting ultrafine particle dispersion is added to methanol, centrifuged, and redispersed in an organic solvent such as hexane.

  Furthermore, in order to obtain n-type CdSe / ZnS used in the present embodiment, as described in “Science” (Dong Yu et al, Science, Vo1 300, 1277-1280 (2003)) After synthesizing the fine particles, they are dried, and potassium deposition is performed under ultra-high vacuum to inject electrons from potassium atoms. Electrons need not be injected into all the ultrafine particles, and n-type CdSe / ZnS and i-type CdSe / ZnS may be mixed locally. Even when the ratio of the number of ultra-fine particles injected with electrons is extremely small, diffusion occurs through the above-described miniband, so that it can be regarded macroscopically as n-type.

  When obtaining p-type CdSe / ZnS, chlorine radicals generated by plasma discharge are attached to inject holes. In this case, similarly to the n-type, p-type CdSe / ZnS ultrafine particles and i-type CdSe / ZnS ultrafine particles may be locally mixed.

  The obtained ultrafine particles are deposited on the transparent electrode 21 (see FIG. 5) in the order of n-type, i-type and p-type by the doctor blade method, and heat treatment is performed. On the thus obtained pin junction photoelectric conversion film 23, a transparent electrode 24 is laminated by sputtering. An organic molecular layer of about 3 nm or less may remain between the CdSe / ZnS ultrafine particles.

  In the above embodiment, CdSe / ZnS ultra particles synthesized in a solution are used, but the production method and type of ultra fine particles are not limited to the above examples. For example, a macroscopic n-type CdSe layer is formed on the surface of the ZnS substrate by utilizing lattice strain in a vacuum. At the initial stage when the CdSe layer is formed, CdSe does not reach a film shape, and CdSe grows into discrete islands. Therefore, at this stage, the formation of CdSe is stopped, and this island-like CdSe is removed. Embed by growth of ZnS. Next, i-type CdSe is similarly formed into an island shape and embedded with ZnS, and then p-type CdSe is similarly formed into an island shape and embedded with ZnS, whereby the photoelectric conversion film 23 is manufactured. May be.

  Also, semiconductor ultrafine particles having a core portion of lnN and an outer shell of GaN can be used instead of CdSe / ZnS. Alternatively, semiconductor ultrafine particles having a core portion of ZnTe and an outer shell of ZnS may be used.

  In addition, if the film thickness of the photoelectric conversion film 23 formed as described above is, for example, a photoelectric conversion film that photoelectrically converts blue light, the blue light is sufficiently absorbed into the next photoelectric conversion film. It is better to prevent light from entering. This is because if blue light is incident on the photoelectric conversion film for green light in the next layer and photoexcitation occurs, color separation becomes worse. However, since the transmittance of blue light transmitted through the blue photoelectric conversion film is a value inherent to the characteristics of the blue photoelectric conversion film, even if blue light is incident on the green photoelectric conversion film of the next layer, The change in green photoelectric conversion signal due to the incidence of blue light can be estimated from the signal intensity of the blue photoelectric conversion film, and can be corrected by signal calculation.

  As a method of moving signal charges from the photoelectric conversion films of FIGS. 1 and 2 to the corresponding high-concentration impurity regions 2 and the like, a method of extracting signals from a light receiving element of a normal CCD image sensor or CMOS image sensor is used. A similar method may be adopted. For example, a method of injecting a certain amount of bias charge into the high-concentration impurity region 2 or the like (storage diode) (refresh mode), accumulating the constant charge by light incidence (photoelectric conversion mode), and then reading the signal charge It is. The photoelectric conversion film itself can be used as a storage diode, or a storage diode can be additionally provided.

  For reading the signal charge moved to the high concentration impurity region 2 or the like, a normal CCD image sensor or CMOS image sensor read method can be applied as it is.

  Conventionally, a solid-state imaging device such as a CCD has a light receiving element having a photoelectric conversion function, a function of storing a converted signal, a function of reading out a stored signal, a function of selecting a pixel position, and the like. The signal charge or signal current photoelectrically converted by the light receiving unit is stored in the light receiving unit itself or an attached capacitor. The stored charges are read out together with the selection of the pixel position by a so-called charge coupled device (CCD) or a MOS type image pickup device (so-called CMOS sensor) using an XY address system.

  The CCD image sensor includes a charge transfer unit that transfers a charge signal of a pixel to an analog shift register by a transfer switch, and sequentially reads the signal to the output terminal by the operation of the register. Examples include a line address type, a frame transfer type, an interline transfer type, and a frame interline transfer type method. The CCD has a two-phase structure, a three-phase structure, a four-phase structure, and a buried channel structure. The structure of the vertical transfer path in the photoelectric conversion film stacked solid-state imaging device of the present invention is one of these. Any structure can be adopted.

  In addition, as an address selection method, there is a method in which each pixel is sequentially selected by a multiplexer switch and a digital shift register and read as a signal voltage (or charge) to a common output line. An image sensor for XY address scanning that is two-dimensionally arrayed is known as a CMOS sensor. This is because the switch provided in the pixel connected to the intersection of XY is connected to the vertical shift register, and is read from the pixel provided in the same row when the switch is turned on by the voltage from the vertical scanning shift register. The signal is read out to the output line in the column direction. This signal is sequentially read from the output through a switch driven by a horizontal scanning shift register.

  For reading out the output signal, a floating diffusion detector or a floating gate detector can be used. Further, S / N can be improved by providing a signal amplifying circuit in the pixel portion, a correlated double sampling method, or the like.

  For signal processing, gamma correction by an ADC circuit, digitization by an AD converter, luminance signal processing, and color signal signal processing can be performed. Examples of the color signal processing include white balance processing, color separation processing, and color matrix processing. When used for NTSC signals, RGB signals can be converted to YIQ signals. These are the same as conventional CCD image sensors and CMOS image sensors.

  In the above-described embodiment, the microlens, the infrared cut filter, and the ultraviolet cut filter have not been described. However, the infrared cut filter can be provided in the lowermost layer or the uppermost layer in the configuration of FIGS. It is also possible to increase the light collection rate using a microlens. In addition, an ultraviolet cut filter may be provided in the uppermost layer, or may be placed at an appropriate position between the lens and the photoelectric conversion film.

  Furthermore, the photoelectric conversion film laminated solid-state imaging device of the present embodiment can have various advantages by making the photoelectric conversion film have a three-layer structure or a four-layer structure. For example, there is no moiré in the captured image, R, G, and B can be detected together with one pixel, so an optical low-pass filter is not required and high resolution is obtained. An imaging lens that has simple processing and does not generate pseudo signals, improves the reproducibility of hair, etc., facilitates pixel mixing and facilitates partial reading, and has an aperture ratio of 100% without using a microlens. There is no shading because there is no restriction on the exit pupil distance with respect to the lens, which makes it suitable for interchangeable lens cameras and contributes to the thinning of the lens, and solves the problems of conventional CCD type and CMOS type image sensors. be able to.

  The photoelectric conversion film laminated solid-state imaging device according to the present invention can be used in place of a conventional CCD type or CMOS type image sensor, and has the advantage that the sensitivity can be increased because one pixel can be made larger than the conventional one. It is useful when mounted on a digital camera or the like.

It is a cross-sectional schematic diagram for 1 pixel of the photoelectric conversion film laminated | stacked solid-state image sensor of the 3 layer structure which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram for 1 pixel of the photoelectric conversion film laminated | stacked solid-state image sensor of the 4 layer structure which concerns on one Embodiment of this invention. It is a graph which shows human visibility. FIG. 3 is a circuit diagram of a signal readout circuit configured by a MOS circuit. It is a cross-sectional schematic diagram of the photoelectric conversion film which concerns on one Embodiment of this invention. It is a schematic diagram of the energy band of the photoelectric conversion film shown in FIG.

Explanation of symbols

1 P well layer 2, 4, 6, 36 High concentration impurity region 3, 5, 7, 37 MOS circuit 8 Gate insulating film 9, 10 Insulating film 11, 14, 16, 19, 21, 24, 32, 33 Transparent electrode Films 12, 17, 22, 35 Electrodes 13, 18, 23, 31 Photoelectric conversion film 25 Transparent insulating film 26 Light shielding film 51 P layer region (mixed region of p-type CdSe / ZnS quantum dots and i-type CdSe / ZnS quantum dots) )
52 n layer region (mixed region of n-type CdSe / ZnS quantum dots and i-type CdSe / ZnS quantum dots)
53 i-layer region (region of i-type CdSe / ZnS quantum dots)
55 p-type CdSe / ZnS quantum dots 56 i-type CdSe / ZnS quantum dots 57 n-type CdSe / ZnS quantum dots

Claims (10)

  A photoelectric conversion film is stacked on a semiconductor substrate on which a signal readout circuit is formed, and a signal corresponding to the amount of incident light photoelectrically converted by the photoelectric conversion film is read out to the outside by the signal readout circuit. In the device, the photoelectric conversion film includes a quantum dot deposition layer, and the deposition layer includes a first deposition layer in which a p-type conductive quantum dot and an i-type conductive quantum dot are mixed, and an n-type conductive layer. A photoelectric conversion film stacked solid-state imaging device, comprising: a second deposited layer obtained by mixing a conductive quantum dot and the i-type conductive quantum dot.   A third deposited layer of the i-type conductive quantum dots not including the p-type conductive quantum dots and the n-type conductive quantum dots is provided between the first deposited layer and the second deposited layer. The photoelectric conversion film laminated solid-state imaging device according to claim 1, wherein   3. The photoelectric device according to claim 1, wherein each quantum dot has a semiconductor ultrafine particle as a core, and the core is covered with a material having an optical band gap energy larger than that of the semiconductor ultrafine particle. Conversion film laminated solid-state imaging device.   4. The photoelectric conversion film stacked solid-state imaging device according to claim 3, wherein the semiconductor ultrafine particles are CdSe, and the material covering the CdSe is ZnS.   4. The photoelectric conversion film stacked solid-state imaging device according to claim 3, wherein the semiconductor ultrafine particles are ZnTe, and the material covering the ZnTe is ZnS. 5.   4. The photoelectric conversion film stacked solid-state imaging device according to claim 3, wherein the semiconductor ultrafine particles are InN, and the material covering the InN is GaN.   The photoelectric conversion film stack according to claim 1, wherein the photoelectric conversion film sandwiched between two transparent electrode films is stacked in three layers via a transparent insulating film. Type solid-state imaging device.   Among the photoelectric conversion films of the three layers, the maximum value of light absorption of the photoelectric conversion film of the first layer is a wavelength of 420 to 500 nm, and the maximum value of light absorption of the photoelectric conversion film of the second layer is a wavelength. The average particle diameter of the quantum dots provided in each photoelectric conversion film is determined so that the maximum value of light absorption of the photoelectric conversion film of the third layer is 500 to 580 nm, and the wavelength is 580 to 660 nm. The photoelectric conversion film laminated solid-state imaging device according to claim 7.   The photoelectric conversion film stack according to any one of claims 1 to 6, wherein the photoelectric conversion film sandwiched between two transparent electrode films is stacked in four layers via a transparent insulating film. Type solid-state imaging device.   Among the four layers of photoelectric conversion films, the maximum value of light absorption of the photoelectric conversion film of the first layer is a wavelength of 420 to 480 nm, and the maximum value of light absorption of the photoelectric conversion film of the second layer is a wavelength. The maximum value of light absorption of the photoelectric conversion film of the third layer is 480 to 520 nm, the wavelength 520 to 580 nm, and the maximum value of light absorption of the photoelectric conversion film of the fourth layer is the wavelength 580 to 660 nm. The photoelectric conversion film stacked solid-state imaging device according to claim 9, wherein an average particle diameter of the quantum dots provided in each photoelectric conversion film is determined.

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