WO2013080769A1 - 固体撮像素子 - Google Patents
固体撮像素子 Download PDFInfo
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- WO2013080769A1 WO2013080769A1 PCT/JP2012/078979 JP2012078979W WO2013080769A1 WO 2013080769 A1 WO2013080769 A1 WO 2013080769A1 JP 2012078979 W JP2012078979 W JP 2012078979W WO 2013080769 A1 WO2013080769 A1 WO 2013080769A1
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- substrate surface
- solid
- fixed charge
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- charge
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/14609—Pixel-elements with integrated switching, control, storage or amplification elements
- H01L27/1461—Pixel-elements with integrated switching, control, storage or amplification elements characterised by the photosensitive area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/1463—Pixel isolation structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/14638—Structures specially adapted for transferring the charges across the imager perpendicular to the imaging plane
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/1464—Back illuminated imager structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/103—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN homojunction type
Definitions
- the present invention relates to a solid-state imaging device typified by a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor.
- CMOS Complementary Metal Oxide Semiconductor
- CCD Charge Coupled Device
- solid-state imaging devices such as CCD image sensors and CMOS image sensors have been mounted on various electronic devices having imaging functions such as imaging devices such as digital video cameras and digital still cameras, and mobile phones with cameras.
- the solid-state imaging device generates charges by photoelectrically converting irradiated light, and generates image data by amplifying a potential due to the charges.
- noise reduction is one of the important issues.
- reduction of dark current which is one of the causes of noise, has become a problem.
- Dark current is generated when charges are supplied to the storage part due to defects in the substrate on which the light receiving part (photodiode) is formed.
- Noise caused by dark current is caused by the charge of the solid-state imaging device. The longer the storage time is, the higher the temperature of the solid-state imaging device is increased.
- the source of dark current is mainly the surface of the substrate.
- Patent Document 1 proposes a solid-state imaging device in which a p-type region is provided around an n-type accumulation unit that accumulates electrons generated by photoelectric conversion.
- an n-type impurity is implanted into a substrate to form a storage portion, and a p-type region is provided by further injecting a p-type impurity into the substrate, and the storage portion is separated from the surface of the substrate. It is configured as follows.
- this solid-state imaging device when the p-type injection amount and the injection area are increased, the photoelectric conversion characteristics and the electric characteristics such as the saturation charge amount deteriorate. Further, when high-temperature heat treatment is performed to activate the p-type impurity, there is a concern that the element structure may be damaged or deteriorated by the heat treatment. Specifically, for example, due to this high-temperature heat treatment, dopants implanted into the substrate before the heat treatment are unintentionally diffused, so that the characteristics of photoelectric conversion, electrical characteristics such as the saturation charge amount, and the like can be deteriorated. Further, in the backside illumination type solid-state imaging device, when p-type implantation is performed on the back surface of the substrate, since elements and wirings are formed on the surface of the substrate, there are many restrictions in subsequent heat treatment.
- Patent Documents 2 and 3 propose a solid-state imaging device in which a fixed charge layer having a negative fixed charge is provided on the surface of a substrate provided with a light receiving portion.
- a fixed charge layer having a negative fixed charge is provided on the surface of a substrate provided with a light receiving portion.
- this solid-state imaging device by providing a fixed charge layer, holes are accumulated on the surface of the substrate, and recombination of the holes and electrons forming a dark current prevents movement of the electrons to the storage unit. , Reduce dark current.
- the lifetime of the charges in the substrate is long.
- the substrate is made of silicon, a sufficient lifetime can be secured.
- the lifetime of the charge forming the dark current is also increased.
- the electrons reach the storage unit before the holes accumulated on the surface of the substrate and the electrons forming the dark current recombine. Can occur. That is, the dark current may not be sufficiently reduced.
- an object of the present invention is to provide a solid-state imaging device that effectively reduces dark current.
- the present invention comprises a substrate made of a semiconductor and having a plurality of pixel regions; A plurality of storage portions formed in the substrate for each pixel region, made of a semiconductor having a conductivity type opposite to that of the substrate and storing charges of a first polarity generated by photoelectric conversion; A fixed charge layer provided above the surface of at least one substrate and having a first fixed charge, The density of integrated charges having a polarity opposite to that of the first fixed charges on the surface of the substrate is changed corresponding to the arrangement of the pixel regions or the arrangement of the accumulation units with respect to a direction parallel to the substrate surface.
- the present invention provides a solid-state imaging device.
- an electric field corresponding to the distribution of the density of integrated charges is generated in the direction parallel to the substrate surface.
- the charges constituting the dark current generated from the defects on the substrate surface not only move toward the accumulation part, but also move along the substrate surface, and the density of the integrated charge is uniform in the direction parallel to the substrate surface.
- route and time until the said electric charge arrives at a storage part become long. Accordingly, it is possible to improve the probability that the charge disappears due to recombination before reaching the accumulation portion.
- the conductivity type of the semiconductor forming the substrate is p-type or n-type.
- the semiconductor forming the storage portion is n-type
- the semiconductor forming the storage portion is p-type.
- the “conductivity type of the semiconductor forming the substrate” indicates the conductivity type of the portion where the element structure of the substrate is formed, and is not limited to the conductivity type of the entire substrate, but indicates the conductivity type of the well. Of course, cases are also included.
- the polarity of the first fixed charge is the first polarity and the polarity of the integrated charge is a second polarity opposite to the first polarity.
- the first polarity charge forming the dark current moves in the second polarity integrated charge opposite to this. Therefore, it is possible to effectively eliminate the charge forming the dark current by recombination.
- the charge accumulated in the accumulation part and the charge forming the dark current are electrons, and the integrated charge is holes. Further, when the first polarity is positive, the charge accumulated in the accumulation unit and the charge forming the dark current are holes, and the integrated charge is electrons.
- the density of the integrated charge on the substrate surface is lower in a region closer to the storage unit and higher in a region away from the storage unit with respect to a direction parallel to the substrate surface. It may be made to become.
- the density of the integrated charge on the substrate surface is lower in a region closer to the storage unit and higher in a region away from the storage unit with respect to a direction parallel to the substrate surface. It may be made to become.
- this solid-state imaging device after a charge that forms a dark current is generated on the substrate surface, the charge is separated from the storage unit due to the influence of an electric field generated in a direction parallel to the substrate surface, or the storage unit The probability of moving toward the storage unit and then moving toward the storage unit increases. In other words, it is possible to lengthen the path and time until the charge forming the dark current reaches the storage unit.
- the probability that the charge moves to the storage part where it should be stored can be improved. become. Therefore, it is possible to suppress the occurrence of color mixing. Further, since only the fixed charge layer is formed above the substrate surface, the implantation of impurities having a conductivity type opposite to that of the accumulation portion can be suppressed, so that the heat treatment accompanying the implantation of the impurities can be suppressed. Therefore, it becomes possible to suppress the destruction of the structure and the deterioration of characteristics due to the heat treatment.
- the density of the first fixed charge in a region near the storage unit of the fixed charge layer and the storage unit of the fixed charge layer in a direction parallel to the substrate surface may be different.
- a heat treatment method applied to a region near the accumulation part of the fixed charge layer in a direction parallel to the substrate surface, and the accumulation part of the fixed charge layer It may be different from the heat treatment method applied to the region away from the region.
- the addition state of the impurity in a region near the accumulation part of the fixed charge layer and the direction of the fixed charge layer in the direction parallel to the substrate surface An impurity addition state in a region away from the accumulation portion may be different.
- the density of the integrated charge in a region near the storage part on the substrate surface and the density of the integrated charge in a region far from the storage part on the substrate surface with respect to a direction parallel to the substrate surface can be provided between them, and an electric field can be generated in the direction.
- the film thickness of a region near the accumulation part of the fixed charge layer and the region away from the accumulation part of the fixed charge layer with respect to a direction parallel to the substrate surface may be different.
- the density of the integrated charge in a region near the storage part on the substrate surface and the density of the integrated charge in a region far from the storage part on the substrate surface with respect to a direction parallel to the substrate surface can be provided between them, and an electric field can be generated in the direction.
- the solid-state imaging device having the above characteristics, at least a part of the material constituting a region close to the storage part of the fixed charge layer with respect to a direction parallel to the substrate surface, and the storage part of the fixed charge layer
- the material may be different from at least a part of the material constituting the region away from.
- the density of the integrated charge in a region near the storage part on the substrate surface and the density of the integrated charge in a region far from the storage part on the substrate surface with respect to a direction parallel to the substrate surface.
- a difference depending on the distribution of the material constituting the fixed charge layer can be provided between them, and an electric field can be generated in the direction.
- a region close to the storage portion of the fixed charge layer or a region away from the storage portion of the fixed charge layer with respect to a direction parallel to the substrate surface is You may make it have the 2nd fixed electric charge of 2nd polarity.
- the distance between the area away from the part and the substrate surface may be different.
- an underlayer made of an insulator provided between the substrate surface and the fixed charge layer is further provided, and a region close to the accumulation portion of the underlayer with respect to a direction parallel to the substrate surface is provided.
- the film thickness may be different from the film thickness of a region of the base layer that is away from the accumulation portion.
- the density of the integrated charge in a region near the storage part on the substrate surface and the density of the integrated charge in a region far from the storage part on the substrate surface with respect to a direction parallel to the substrate surface.
- a difference according to the distribution of the distance between the substrate surface and the fixed charge layer can be provided between them, and an electric field can be generated in the direction.
- a barrier portion having a higher impurity concentration than the surroundings is formed in a region away from the accumulation portion of the substrate in a direction parallel to the substrate surface.
- the potential barrier between adjacent storage units becomes clear, and it is possible to improve the probability that charges generated by photoelectric conversion move to the storage unit that should be stored. . Therefore, it is possible to suppress the occurrence of color mixing.
- an attracting portion made of a semiconductor having a conductivity type opposite to that of the substrate may be formed on the substrate surface side of the barrier portion.
- this solid-state imaging device it is possible to confine the charge forming the dark current on the substrate surface. Therefore, it is possible to further improve the probability that the charge forming the dark current disappears due to recombination before reaching the storage portion.
- a region close to the accumulation unit above the fixed charge layer or a distance from the accumulation unit above the fixed charge layer with respect to a direction parallel to the substrate surface An electrode layer provided in the region, It is preferable that a voltage having the same polarity as the first fixed charge is applied to the electrode layer at least during a period in which the charge having the first polarity is accumulated in the accumulation unit.
- this solid-state imaging device it is possible to increase the density difference of the integrated charges at least during the period in which charges are accumulated in the accumulation unit. Therefore, it is possible to increase the generated electric field with respect to the direction parallel to the substrate surface.
- a separation portion having an impurity concentration higher than that of the surroundings is formed at the boundary of the pixel region in the substrate.
- the potential barrier can be increased at the boundary of the pixel region in the substrate. For this reason, it is possible to efficiently move the charge generated by the photoelectric conversion in each pixel region to the storage unit in the pixel region and store it.
- the pixel region can be defined as a region sandwiched between the separation portions. In this case, if the density of the integrated charge in the direction parallel to the substrate surface changes corresponding to the arrangement of the pixel regions, it can be said that the density changes corresponding to the arrangement of the separation portions.
- the solid-state imaging device having the above characteristics further includes a wiring layer that is provided on the first substrate surface side of the substrate and controls the charge of the first polarity accumulated in the accumulation unit, The light is incident on the substrate from the second substrate surface opposite to the first substrate surface, and the storage unit accumulates the charge of the first polarity generated by photoelectric conversion of the light, It is preferable that the fixed charge layer is provided at least above the surface of the second substrate.
- the dark current can be effectively reduced in the back-illuminated solid-state imaging device.
- the fixed charge layer includes: It is preferable that at least one of hafnium oxide, aluminum oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, zinc oxide, yttrium oxide, lanthanoid oxide, silicon oxide, nickel oxide, cobalt oxide, and copper oxide is included.
- the film thickness at the center of the region of the fixed charge layer immediately above the storage portion is 0.75 ⁇ ⁇ 500 / (4 ⁇ N) + K ⁇ 500 / (2 ⁇ N) ⁇ nm or more, and It is preferable to be 1.25 ⁇ ⁇ 560 / (4 ⁇ N) + K ⁇ 560 / (2 ⁇ N) ⁇ nm or less.
- the solid-state imaging device having the above characteristics, it is possible to improve the probability that the charge forming the dark current disappears due to recombination before reaching the storage unit, and thus the dark current can be effectively reduced. become.
- FIG. 1 is a cross-sectional view illustrating an example of the overall structure of a solid-state image sensor according to an embodiment of the present invention.
- the principal part sectional view showing the 1st example of the structure for reducing dark current in the solid-state image sensing device concerning the embodiment of the present invention.
- the principal part sectional drawing which shows the 2nd specific example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows the 3rd specific example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows the 4th specific example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows the 5th example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows the 6th specific example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows the 7th specific example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows an example of the structure of a solid-state image sensor in the case of providing the pixel which is not irradiated with light.
- the principal part sectional drawing which shows another example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows another example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows another example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the principal part sectional drawing which shows another example of the structure for reducing a dark current in the solid-state image sensor which concerns on embodiment of this invention.
- the solid-state imaging device to which the present invention can be applied is not limited to such a back-illuminated solid-state imaging device, and can also be applied to a front-illuminated solid-state imaging device.
- FIG. 1 is a cross-sectional view showing an example of the overall structure of a solid-state imaging device according to an embodiment of the present invention.
- hatching indicating a cross section is omitted for clarity of illustration.
- the solid-state imaging device 1 includes a substrate 10, a storage unit 11 that is formed in the substrate 10 and accumulates electric charges generated by photoelectric conversion, and one surface of the substrate 10 (hereinafter referred to as a first substrate surface). 101) and a base layer provided on the other surface of the substrate 10 (the surface opposite to the first substrate surface 101, hereinafter referred to as the second substrate surface 102). 13, a fixed charge layer 14 provided on the base layer 13 and having a positive or negative fixed charge, an insulating layer 15 provided on the fixed charge layer 14 and made of an insulator, and a predetermined charge provided on the insulating layer 15.
- a color filter 16 that selectively transmits light of a specific color (wavelength)
- an on-chip lens 17 that is provided on the color filter 16 and collects incident light and communicates with the color filter 16, and a pixel region of the substrate 10 Comprising the separating portion 18 formed at the boundary, the.
- the substrate 10 is made of a p-type or n-type semiconductor.
- the storage unit 11 is made of a semiconductor having a conductivity type opposite to that of the substrate 10, and the substrate 10 and the storage unit 11 constitute a photodiode.
- the storage unit 11 is formed in a central region of the pixel region A in the substrate 10 (in the middle of the adjacent separation unit 18) and in a direction parallel to the second substrate surface 102 (and the first substrate surface 101).
- FIG. 1 illustrates a state in which the pixel region A and the storage unit 11 are arranged with a predetermined interval with respect to the horizontal direction of the paper surface, the pixel region A and the storage unit 11 are in the depth direction of the paper surface. Are arranged with a predetermined interval.
- the color filter 16 and the on-chip lens 17 are also arranged in the same manner as the pixel area A and the storage unit 11. Specifically, for example, the pixel area A, the storage unit 11, the color filter 16, and the microchip lens 17 are arranged in a matrix form (in a Bayer arrangement when focusing on the color filter 16).
- the isolation part 18 is made of a semiconductor having the same conductivity type as that of the substrate 10, and the impurity concentration thereof is higher than the impurity concentration of the surrounding substrate 10 (potential barrier is increased). Therefore, in each pixel area A, the charges generated by the photoelectric conversion efficiently move to the accumulation unit 11 in the pixel area A and are accumulated. Note that the pixel area A can also be defined as an area sandwiched between the separation portions 18.
- the light incident on the solid-state imaging device 1 is collected by the on-chip lens 17 and passed through the color filter 16.
- the color filter 16 selectively transmits light of a predetermined color (wavelength).
- the light that has passed through the color filter 16 passes through the insulating layer 15, the fixed charge layer 14, and the base layer 13, and enters the substrate 10 from the second substrate surface 102.
- electrons and holes are generated by photoelectric conversion of incident light, and one of them is stored in the storage unit 11.
- the wiring layer 12 includes an insulator and a conductor such as a wiring or an electrode formed in the insulator in accordance with the charge processing method employed by the solid-state imaging device 1.
- the conductor included in the wiring layer 12 includes a gate electrode for transferring charges accumulated in the accumulation unit 11 to another region in the substrate 10, and charges accumulated in the accumulation unit 11 in the substrate 10. Electrodes and wiring for reading out.
- the underlayer 13 is provided between the second substrate surface 102 and the fixed charge layer 14, and the fixed charge layer 14 has positive or negative fixed charges on the second substrate surface 102 with the underlayer 13 interposed therebetween.
- the density of the integrated charge on the second substrate surface 102 is changed in accordance with the periodicity of the arrangement of the storage units 11 with respect to the direction parallel to the second substrate surface 102.
- Each part is configured (a specific example will be described later).
- an electric field corresponding to the distribution of the density of integrated charges is generated in the direction parallel to the second substrate surface 102. Therefore, the charges forming the dark current resulting from the defects on the second substrate surface 102 not only move toward the storage unit 11 but also move along the second substrate surface 102 and are parallel to the second substrate surface 102. Compared to the case where the density of the integrated charge is uniform with respect to the direction, the path and time until the charge reaches the storage unit 11 becomes longer. Therefore, it is possible to improve the probability that the charge disappears due to recombination before reaching the storage unit 11, and it is possible to reduce the dark current.
- the substrate 10 is made of a p-type (p) semiconductor
- the storage unit 11 is made of an n-type (n ⁇ ) semiconductor, and stores electrons generated by photoelectric conversion.
- p p-type
- n ⁇ n-type
- the integrated charge density on the second substrate surface 102 is a region close to the storage unit 11 in a direction parallel to the second substrate surface 102 (for example, a region immediately above the storage unit 11; hereinafter, particularly referred to. As long as there is no region, the same is true for the portion described as “region close to the storage unit 11”.
- the region is higher from the storage unit 11 (for example, the region between the regions directly above and the boundary region of the pixel region A (separation (A region immediately above the portion 18)
- the semiconductor constituting the substrate 10 is p-type indicates that the conductivity type of the portion of the substrate 10 where the element structure is formed is p-type, and the conductivity type of the entire substrate 10 is p-type.
- the present invention is not limited to the case, and a case where the conductivity type of the well is p-type (for example, a case where a p-type well is formed on an n-type substrate as a whole) is also included.
- the substrate 10 is made of, for example, silicon.
- boron, boron fluoride, or the like can be used as the p-type impurity.
- phosphorus, arsenic, or the like can be used as the n-type impurity.
- these impurities are implanted into the substrate 10 or the like by applying a method such as ion implantation.
- the storage unit 11 is formed by implanting n-type impurities into the substrate 10 from the first substrate surface 101.
- the storage portion 11 may be provided at a position separated from the first substrate surface 101 by further injecting p-type impurities into the substrate 10 from the first substrate surface 101. (It may be an embedded photodiode).
- the insulator provided in the insulating layer 15 and the wiring layer 12 is made of, for example, silicon oxide.
- the fixed charge layer 14 in the specific example described below includes negative fixed charges.
- hafnium oxide, aluminum oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, zinc oxide, yttrium oxide, lanthanoid oxide, and silicon oxide although depending on film forming conditions such as impurities, etc.
- Has a negative fixed charge for example nickel oxide, cobalt oxide and copper oxide have a positive fixed charge.
- the fixed charge layer 14 may be provided with at least one of these materials.
- An impurity such as silicon or nitrogen may be added to the fixed charge layer 14.
- the base layer 13 is made of an insulator such as silicon oxide, silicon nitride, or silicon oxynitride. This is preferable because the density of defects that cause dark current can be reduced on the second substrate surface 102 of the substrate 10 on which the underlayer 13 is formed.
- each specific example of the structure for reducing dark current described below can be implemented by combining a part or all of them as long as there is no contradiction.
- FIG. 2 A first specific example of a structure for reducing dark current will be described with reference to FIG. Note that the thick solid arrow shown in FIG. 2 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of the first specific example is applied. . On the other hand, the broken-line arrows shown in FIG. 2 indicate paths that are likely to follow when the charge d forming the dark current does not recombine when the structure of the first specific example is not applied.
- the density of the negative fixed charge E in the region near the storage portion 11 of the fixed charge layer 14a is high with respect to the direction parallel to the second substrate surface 102.
- the density of the negative fixed charge E in the region away from the storage part 11 of the fixed charge layer 14a is lowered. Therefore, the density of the integrated charge h on the second substrate surface 102 is higher in the region closer to the storage unit 11 and lower in the region away from the storage unit 11 in the direction parallel to the second substrate surface 102, and the direction Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the first specific example is not applied (when the density of the integrated charge h is uniform with respect to the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and the charge d reaches the storage unit 11 until the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the fixed charge layer 14a is formed by, for example, a heat treatment method applied to a region near the storage unit 11 of the fixed charge layer 14a in a direction parallel to the second substrate surface 102, and the storage unit 11 of the fixed charge layer 14a. It can be obtained by differentiating the heat treatment method applied to the region away from the region.
- the fixed charge layer 14a is made of a material (hafnium oxide or the like) that can increase the negative fixed charge E by crystallization by heat treatment after film formation
- the heat treatment temperature is changed according to the above region (negative The region where the fixed charge E density should be increased is heat-treated at a high temperature, and the region where the negative fixed charge E density should be decreased is heat-treated at a low temperature), whereby the fixed charge layer 14a can be obtained.
- the fixed charge layer 14a includes, for example, an impurity addition state in a region near the storage unit 11 of the fixed charge layer 14a and a storage unit of the fixed charge layer 14a in a direction parallel to the second substrate surface 102. It can also be obtained by making the impurity addition state in a region away from 11 different. For example, an impurity that can reduce the density of the negative fixed charge E (or an impurity that can increase the density of the negative fixed charge E or both) can be selectively selected depending on the region.
- the above-mentioned fixed charge layer 14a can be obtained by adding or changing the amount added to each region.
- ⁇ Second specific example> A second specific example of a structure for reducing dark current will be described with reference to FIG.
- the thick solid line arrow shown in FIG. 3 indicates a path that is likely to be followed when the charge d forming the dark current does not recombine when the structure of the second specific example is applied.
- the broken-line arrow shown in FIG. 3 indicates a path that is likely to be followed when the charge d forming the dark current does not recombine when the structure of the second specific example is not applied.
- the film thickness in the region near the storage portion 11 of the fixed charge layer 14b is large in the direction parallel to the second substrate surface 102, and the fixed charge layer 14b The film thickness in a region away from the storage unit 11 is reduced. Therefore, the density of the integrated charge h on the second substrate surface 102 is higher in the region closer to the storage unit 11 and lower in the region away from the storage unit 11 in the direction parallel to the second substrate surface 102, and the direction Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the second specific example is not applied (when the density of the integrated charge h is uniform with respect to the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and the charge d reaches the storage unit 11 until the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the fixed charge layer 14b can be formed, for example, by etching a region where the film thickness is to be reduced after forming a film having a uniform film thickness, or a region where the film thickness is to be increased.
- the film can be formed by selectively forming a film.
- FIG. 4 A third specific example of a structure for reducing dark current will be described with reference to FIG. Note that the thick solid arrow shown in FIG. 4 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of the third specific example is applied. . On the other hand, the broken-line arrows shown in FIG. 4 indicate paths that are likely to follow when the charge d forming the dark current does not recombine when the structure of the third specific example is not applied.
- the region 141 near the accumulation unit 11 of the fixed charge layer 14 c is negative fixed charge E with respect to the direction parallel to the second substrate surface 102.
- the fixed charge layer 14c at least a part of the region 142 away from the accumulation portion 11 is formed of a material having a low negative fixed charge E density. Therefore, the density of the integrated charge h on the second substrate surface 102 is higher in the region closer to the storage unit 11 and lower in the region away from the storage unit 11 in the direction parallel to the second substrate surface 102, and the direction Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then influenced by the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the third specific example is not applied (when the density of the integrated charge h is uniform with respect to the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the fixed charge layer 14c can be formed, for example, by separately forming the regions 141 and 142. Further, the same effect can be obtained by forming at least a part of the region 141 and the region 142 with materials having different densities of the negative fixed charge E, or with materials having different work functions. . In this case, at least a part of the region 141 may be formed of a material having a large work function difference, and at least a part of the region 142 may be formed of a material having a small work function difference (similar to the work function of silicon).
- FIG. 5 A fourth specific example of a structure for reducing dark current will be described with reference to FIG.
- the thick solid line arrow shown in FIG. 5 indicates a path that is likely to be traced when the charge d forming the dark current does not recombine when the structure of the fourth specific example is applied.
- the broken-line arrows shown in FIG. 5 indicate paths that are likely to be followed when the charge d forming the dark current does not recombine when the structure of the fourth specific example is not applied.
- the region near the storage portion 11 of the fixed charge layer 14d has a negative fixed charge E with respect to the direction parallel to the second substrate surface 102, and is fixed.
- a region of the charge layer 14d away from the storage unit 11 has a positive fixed charge H. Therefore, the density of the accumulated charges h (holes) on the second substrate surface 102 is higher in a region closer to the storage unit 11 and lower in a region away from the storage unit 11 in the direction parallel to the second substrate surface 102.
- There is an integrated charge e (electron) and an electric field is generated in that direction. In particular, a larger electric field is generated than an electric field generated only by the density difference of the integrated charges h.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the fourth specific example is not applied (when the density of the integrated charge h is uniform in the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 becomes longer, and the charge d reaches the storage unit 11 until the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- a larger electric field can be generated in the direction parallel to the second substrate surface 102. Therefore, the charge d disappears by recombination before reaching the storage unit 11. It is possible to further improve the probability of performing. Further, since the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the fixed charge layer 14d is at least a part of the fixed charge layer 14d that is close to the storage unit 11 in the direction parallel to the second substrate surface 102, for example, as in the third specific example. It can be obtained by differentiating the material and at least a part of the material constituting the region away from the storage portion 11 of the fixed charge layer 14d.
- silicon nitride or silicon oxynitride can be used as a material having a positive fixed charge.
- the fixed charge layer 14d has an impurity addition state in a region near the storage portion 11 of the fixed charge layer 14d with respect to a direction parallel to the second substrate surface 102, as in the first specific example. It can also be obtained by making the impurity addition state in a region away from the storage portion 11 of the fixed charge layer 14d different.
- FIG. 6 A fifth specific example of a structure for reducing dark current will be described with reference to FIG.
- the thick solid line arrow shown in FIG. 6 indicates a path that is likely to be traced when the charge d forming the dark current does not recombine when the structure of the fifth specific example is applied.
- the broken-line arrows shown in FIG. 6 indicate paths that are likely to be followed when the charge d forming the dark current does not recombine when the structure of the fifth specific example is not applied.
- the film thickness in the region near the storage part 11 of the base layer 13e is small in the direction parallel to the second substrate surface 102, and the storage part of the base layer 13e
- the film thickness in a region away from 11 increases.
- the distance between the region near the accumulation part 11 of the fixed charge layer 14e and the second substrate surface 102 in the direction parallel to the second substrate surface 102 is small, and the distance from the accumulation part 11 of the fixed charge layer 14e is reduced.
- the distance between the distant region and the second substrate surface 102 increases. Therefore, the density of the integrated charge h on the second substrate surface 102 is higher in the region closer to the storage unit 11 and lower in the region away from the storage unit 11 in the direction parallel to the second substrate surface 102, and the direction Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the fifth specific example is not applied (when the density of the integrated charge h is uniform in the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the underlayer 13e can be formed, for example, by etching a region where the film thickness should be reduced after forming a film having a uniform film thickness, or in a region where the film thickness should be increased. Alternatively, it can be formed by selectively forming a film. Furthermore, the above-described fixed charge layer 14e can be obtained by performing uniform film formation on the underlying layer 13e on which the unevenness is thus formed.
- FIG. 7 A sixth specific example of a structure for reducing dark current will be described with reference to FIG. Note that the thick solid line arrow shown in FIG. 7 may be traced when the charge d forming the dark current and the charge c generated by photoelectric conversion do not recombine when the structure of the sixth specific example is applied. Indicates a high path. On the other hand, the dashed arrow shown in FIG. 7 may be traced when the charge d forming the dark current and the charge c generated by photoelectric conversion do not recombine when the structure of the sixth specific example is not applied. It shows a high route.
- the structure of the sixth specific example includes a fixed charge layer 14f similar to the fixed charge layer 14a (see FIG. 2) shown in the first specific example, and is parallel to the second substrate surface 102.
- An electric field is generated with respect to the direction.
- a p-type (p + ) barrier having an impurity concentration higher than that of the surrounding area in a region away from the storage portion 11 of the substrate 10 with respect to a direction parallel to the second substrate surface 102. Part 19 is formed.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- the structure of the sixth specific example is not applied (when the density of the integrated charge h is uniform in the direction parallel to the second substrate surface 102), as shown by the broken line in FIG. After the charge d forming the second substrate surface 102 is generated, the probability of moving directly toward the storage unit 11 increases.
- the electric charge c generated by the photoelectric conversion is generated in the substrate 10 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102.
- the movement is hindered by the barrier portion 19 and the probability of moving toward the lower accumulation portion 11 is increased.
- the influence of the electric field generated in the direction parallel to the second substrate surface 102 as shown by the broken line in FIG. And moves away from the storage unit 11, and the probability of moving to the adjacent storage unit 11 instead of the storage unit 11 that should be stored is increased.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and the charge d reaches the storage unit 11.
- the probability of disappearing due to recombination can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the potential barrier between the adjacent storage units 11 becomes clear, so that the charge c generated by photoelectric conversion moves to the storage unit 11 that should be stored originally. Probability can be improved. Therefore, it is possible to suppress the occurrence of color mixing.
- the barrier portion 19 can be formed by implanting p-type impurities into the substrate 10, for example.
- the p-type impurity may be implanted into the substrate 10 from the second substrate surface 102 side, or may be implanted into the substrate 10 from the first substrate surface 101 side, or both. Also good. Further, when the p-type impurity is implanted into the substrate 10 from the first substrate surface 101 side, the wiring layer 12 or the like is not yet formed at the time when the p-type impurity is implanted into the substrate 10. Heat treatment can be performed.
- the fixed charge layer 14f in the sixth specific example is the same as the fixed charge layer 14a (see FIG. 2) in the first specific example, but the fixed charge layer in the other specific examples. It may be the same as or other than these.
- a seventh specific example of the structure for reducing dark current will be described.
- the thick solid arrow shown in FIG. 8 may be traced when the charge d forming the dark current and the charge c generated by photoelectric conversion do not recombine when the structure of the seventh specific example is applied. Indicates a high path.
- the broken-line arrow shown in FIG. 8 may be traced when the charge d forming the dark current and the charge c generated by photoelectric conversion do not recombine when the structure of the seventh specific example is not applied. It shows a high route.
- the structure of the seventh specific example includes a fixed charge layer 14 g similar to the fixed charge layer 14 a (see FIG. 2) shown in the first specific example, and is parallel to the second substrate surface 102. An electric field is generated with respect to the direction. Furthermore, in the structure of the seventh specific example, a barrier portion 19 similar to the barrier portion shown in the sixth specific example (see FIG. 7) is formed, and n-type (on the second substrate surface 102 side of the barrier portion 19). n) Attraction part 20 is formed
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the attracting unit 20 increases.
- the structure of the seventh specific example is not applied (when the density of the integrated charge h is uniform with respect to the direction parallel to the second substrate surface 102), as shown by the broken line in FIG.
- the charge d that forms the following is generated on the second substrate surface 102, and then increases in the probability of moving directly toward the storage unit 11.
- the electric charge c generated by the photoelectric conversion is generated in the substrate 10 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102.
- the movement is hindered by the barrier portion 19 and the probability of moving toward the lower accumulation portion 11 is increased.
- the structure of the seventh specific example is not applied (when the barrier portion 19 and the attracting portion 20 are not formed), as shown by the broken line in FIG. 8, it occurs in the direction parallel to the second substrate surface 102.
- the probability of moving away from the storage unit 11 due to the influence of the electric field and moving to the adjacent storage unit 11 instead of the storage unit 11 that should be stored increases.
- the charge d forming the dark current can be confined in the second substrate surface 102, and the charge d forming the dark current reaches the storage unit 11. Since the path and time until the charge is increased, the probability that the charge d disappears due to recombination before reaching the storage unit 11 can be further improved. Further, since the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- the potential barrier between adjacent storage units becomes clear, and thus the probability that the charge c generated by photoelectric conversion moves to the storage unit 11 that should be stored originally Can be improved. Therefore, it is possible to suppress the occurrence of color mixing.
- the attraction portion 20 can be formed, for example, by injecting an n-type impurity into the barrier portion 19 formed in the substrate 10 from the second substrate surface 102 side.
- the fixed charge layer 14g in the seventh specific example is the same as the fixed charge layer 14a (see FIG. 2) in the first specific example. It may be the same as or other than these.
- FIG. 9 is a top view of the substrate for explaining an example of a method for forming the barrier portion and the attracting portion.
- FIG. 9 is a top view when the substrate 10 is viewed from the second substrate surface 102 side.
- the resists R1 and R2 are disposed at least immediately above the storage portion 11 to implant impurities. Is to do.
- the resist R1 shown in FIG. 9A is a quadrangle
- the resist R2 shown in FIG. 9B is a circle.
- the resists R1 and R2 are preferably polygons that are equal to or larger than a quadrangle, and are circular as shown in FIG. 9B. Further preferred.
- a pixel (optical black) that is not irradiated with light may be provided at the end of the solid-state imaging device 1 in order to detect noise components such as dark current.
- FIG. 10 is a cross-sectional view of the main part showing an example of the structure of the solid-state imaging device in the case where pixels that are not irradiated with light are provided.
- a structure in the case where pixels that are not irradiated with light are provided for the solid-state imaging device of the first specific example described above will be exemplified.
- a light blocking layer 21 that blocks light incident on the substrate 10 is provided immediately above the storage portion 11 (left end in the figure) included in the pixel.
- the light-shielding layer 21 is provided on the fixed charge layer 14a, it is possible to make the behavior of the charges forming the dark current uniform in the pixel and other normal pixels, and this occurs in the storage unit 11 of each pixel. This is preferable because the difference in dark current can be reduced.
- the density of the integrated charge h on the second substrate surface 102 is higher in the region closer to the storage unit 11 and lower in the region farther from the storage unit 11 in the direction parallel to the second substrate surface 102.
- the density distribution of the integrated charge h may be the reverse of the structure of each of the specific examples described above. That is, the density of the integrated charge h on the second substrate surface 102 may be lower in a region closer to the storage unit 11 and higher in a region away from the storage unit 11 in a direction parallel to the second substrate surface 102.
- FIG. 11 is a cross-sectional view of a main part showing another example of a structure for reducing dark current in the solid-state imaging device according to the embodiment of the present invention.
- the thick solid arrow shown in FIG. 11 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of this example is applied.
- the broken-line arrow shown in FIG. 11 indicates a path that is likely to be followed when the charge d forming the dark current does not recombine when the structure of this example is not applied.
- FIG. 2 another structure corresponding to the structure of the first specific example described above (see FIG. 2) is illustrated.
- the density of the negative fixed charge E in the region near the storage portion 11 of the fixed charge layer 14p is low in the direction parallel to the second substrate surface 102, and the fixed charge
- the density of the negative fixed charge E in the region away from the accumulation part 11 of the layer 14p increases. Therefore, the density of the integrated charge h on the second substrate surface 102 is lower in the region closer to the storage unit 11 and higher in the region away from the storage unit 11 with respect to the direction parallel to the second substrate surface 102. Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then influenced by the electric field generated in the direction parallel to the second substrate surface 102. In response, the probability of moving closer to the storage unit 11 and then moving toward the storage unit 11 increases.
- a dark current is generated as shown by the broken line in FIG. After the charge d is generated on the second substrate surface 102, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and recombination is performed before the charge d reaches the storage unit 11.
- the probability of disappearing can be improved.
- the charge d (electron) moves in the integrated charge h (hole), the charge d can be effectively extinguished by recombination.
- charges (electrons) generated by photoelectric conversion move in a direction parallel to the second substrate surface 102, not in a direction away from the storage unit 11, but in an approaching direction. Therefore, it is possible to improve the probability that charges generated by photoelectric conversion move to the storage unit 11 that should be stored. Therefore, it is possible to suppress the occurrence of color mixing.
- the color mixture can be suppressed by providing the barrier portion 19.
- the barrier portion 19 it is necessary to inject impurities into the substrate 10 and perform heat treatment. Depending on the timing and temperature of the heat treatment, the structure formed so far may be destroyed, There is a possibility of deteriorating characteristics.
- the structure of this example only the fixed charge layer 14p is formed above the second substrate surface 102, and the implantation of the p-type impurity having the conductivity type opposite to that of the storage portion 11 is suppressed. Therefore, the heat treatment accompanying the implantation of the p-type impurity can be suppressed. Therefore, it becomes possible to suppress the destruction of the structure and the deterioration of characteristics due to the heat treatment.
- FIG. 12 is a cross-sectional view of a main part showing another example of a structure for reducing dark current in the solid-state imaging device according to the embodiment of the present invention.
- the thick solid arrow shown in FIG. 12 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of this example is applied.
- the broken-line arrows shown in FIG. 12 indicate paths that are likely to follow when the charge d forming the dark current does not recombine when the structure of this example is not applied.
- FIG. 2 another structure corresponding to the structure of the first specific example described above (see FIG. 2) is illustrated.
- the density of the positive fixed charge H in the region near the storage part 11 of the fixed charge layer 14q is high in the direction parallel to the second substrate surface 102, and the fixed charge The density of the positive fixed charge H in the region away from the storage portion 11 of the layer 14q is lowered. Therefore, the density of the integrated charge e on the second substrate surface 102 is higher in a region closer to the storage unit 11 and lower in a region away from the storage unit 11 in the direction parallel to the second substrate surface 102, Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. In response, the probability of moving closer to the storage unit 11 and then moving toward the storage unit 11 increases.
- a dark current is generated as shown by the broken line in FIG. After the charge d is generated on the second substrate surface 102, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 11 is increased, and recombination is performed before the charge d reaches the storage unit 11.
- the probability of disappearing can be improved.
- the electric charge d generated by the photoelectric conversion moves in the approaching direction in the direction parallel to the second substrate surface 102, not in the direction away from the storage unit 11. Therefore, it is possible to improve the probability that charges generated by photoelectric conversion move to the storage unit 11 that should be stored. Therefore, it is possible to suppress the occurrence of color mixing. Further, in the structure of this example, it is possible to suppress the occurrence of color mixing only by forming the fixed charge layer 14q above the second substrate surface 102.
- the charge d (electron) moves in the integrated charge e (electron). Therefore, in the structure of this example, there is a possibility that the charge d is difficult to disappear by recombination as compared with the structures of the specific examples described above. However, even with the structure of this example, the charge d can be suitably eliminated by increasing the concentration of the p-type impurity in the substrate 10.
- the density of the accumulated charge e on the second substrate surface 102 is higher in the region closer to the storage unit 11 in the direction parallel to the second substrate surface 102, and away from the storage unit 11.
- the region has been described as being lower (see FIG. 12)
- the density distribution of the integrated charge e may be the reverse of [4] above. That is, the density of the accumulated charge e on the second substrate surface 102 may be lower in a region closer to the storage unit 11 and higher in a region away from the storage unit 11 in a direction parallel to the second substrate surface 102.
- FIG. 13 is a cross-sectional view of a main part showing another example of a structure for reducing dark current in the solid-state imaging device according to the embodiment of the present invention.
- a thick solid line arrow shown in FIG. 13 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of this example is applied.
- the broken-line arrows shown in FIG. 13 indicate paths that are likely to be followed when the charge d forming the dark current does not recombine when the structure of this example is not applied.
- FIG. 2 another example structure corresponding to the structure of the first example described above (see FIG. 2) will be illustrated.
- the density of the positive fixed charge H in the region near the storage portion 11 of the fixed charge layer 14r is low in the direction parallel to the second substrate surface 102, and the fixed charge The density of the positive fixed charge H in the region away from the storage portion 11 of the layer 14r is increased. Therefore, the density of the integrated charge e on the second substrate surface 102 is lower in the region closer to the storage unit 11 and higher in the region away from the storage unit 11 with respect to the direction parallel to the second substrate surface 102. Produces an electric field.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. And moves away from the storage unit 11, and then the probability of moving toward the storage unit 11 increases.
- a dark current is generated as shown by the broken line in FIG. After the charge d is generated on the second substrate surface 102, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 13 is increased, and recombination is performed before the charge d reaches the storage unit 11.
- the probability of disappearing can be improved.
- the charge d can be suitably eliminated by increasing the concentration of the p-type impurity in the substrate 10.
- FIG. 14 is a cross-sectional view of a main part showing another example of the structure for reducing dark current in the solid-state imaging device according to the embodiment of the present invention.
- FIG. 15 is a top view of the substrate for explaining an example of the structure of the electrode layer.
- the thick solid arrow shown in FIG. 14 indicates a path that is likely to follow when the charge d forming the dark current does not recombine when the structure of this example is applied.
- the broken-line arrows shown in FIG. 14 indicate paths that are likely to follow when the charge d forming the dark current does not recombine when the structure of this example is not applied.
- a structure in which the electrode layer 22 is provided with respect to the structure described in the above [3] is illustrated.
- the region (the density of the negative fixed charge E is high) away from the accumulation portion 11 of the fixed charge layer 14 p in the direction parallel to the second substrate surface 102.
- the electrode layer 22 is provided above the region. Further, a voltage having the same polarity (negative) as that of the fixed charge E is applied to the electrode layer 22 at least during a period in which the storage unit 11 stores charges (electrons) generated by photoelectric conversion. Therefore, compared with the structure described in the above [3] (see FIG. 11), the density of the accumulated charges h on the second substrate surface 102 is higher in the accumulation unit 11 than in the direction parallel to the second substrate surface 102. The closer the region, the lower the region, and the higher the region away from the storage unit 11, the higher the electric field can be generated in that direction.
- the electric charge d forming the dark current is generated on the second substrate surface 102 and then the influence of the electric field generated in the direction parallel to the second substrate surface 102. In response, the probability of moving closer to the storage unit 11 and then moving toward the storage unit 11 increases.
- a dark current is generated as shown by the broken line in FIG. After the charge d is generated on the second substrate surface 102, the probability of moving directly toward the storage unit 11 increases.
- the path and time until the charge d forming the dark current reaches the storage unit 13 is increased, and recombination is performed before the charge d reaches the storage unit 11.
- the probability of disappearing can be improved.
- the electrode layer 22 is made of a material that does not transmit the light incident on the substrate 10, as described above, the electrode layer 22 is separated from the accumulation portion 11 of the fixed charge layer 14 p in the direction parallel to the second substrate surface 102. It is preferable to provide the electrode layer 22 above the region. However, when the electrode layer 22 is made of a material that can transmit light incident on the substrate 10, it may be disposed at any position on the fixed charge layer. That is, the structure of this example (the structure including the electrode layer 22 above the fixed charge layer) can be applied to the structure of each example described above.
- the storage unit 11 is arranged in the center of the pixel region A has been described so far (see FIGS. 2 to 8 and 10 to 15).
- the storage unit 11 is provided in the wiring layer 12, for example.
- the pixel region A may be arranged at a location other than the center.
- FIG. 16 is a cross-sectional view of the main part showing another example of the structure for reducing dark current in the solid-state imaging device according to the embodiment of the present invention.
- FIG. 2 another structure corresponding to the structure of the first specific example described above (see FIG. 2) is illustrated.
- the storage unit 11 is arranged at a position close to the separation unit 18 from the center of the pixel region A. Specifically, for example, with respect to a certain direction parallel to the second substrate surface 102, a separation unit 18 where the adjacent storage units 11 are close together, and a separation unit 18 where the adjacent storage units 11 are separated from each other.
- the storage units 11 are arranged with periodicity so as to be repeated alternately.
- the density of the integrated charge h is higher toward the center of the pixel region A (away from the separation unit 18) in the direction parallel to the second substrate surface 102, and toward the end of the pixel region A ( It is lower as the separation unit 18 is approached, and is the same as the first specific example (see FIG. 2) described above. That is, in the structure of this example, the density of the integrated charge h changes corresponding to the arrangement of the pixel regions A (or the separation portions 18).
- the density of the integrated charge h may be changed in correspondence with the arrangement of the storage unit 11 without changing in correspondence with the arrangement of the pixel region A (or the separation unit 18). Specifically, for example, in the structure shown in FIG. 16, the density of the integrated charge h is higher in a region closer to the storage unit 11 (a region immediately above the storage unit 11) with respect to a direction parallel to the second substrate surface 102. You may make it low as the area
- the refractive index can be made larger than the material (for example, silicon oxide) constituting the other layers.
- the fixed charge layer can be used as an inner lens, and color mixing can be reduced, which is preferable.
- the refractive index difference between the fixed charge layer and another adjacent layer becomes large, there is a concern that the light that is about to enter the substrate 10 is reflected by the fixed charge layer, and the sensitivity of the solid-state imaging device is lowered.
- the fixed charge layer film so that the reflection of the green light is suppressed with reference to the green light (for example, 500 nm or more and 560 nm or less) having an intermediate wavelength in the light transmitted through the color filter. It is preferable to adjust the thickness.
- the film thickness at the center of the region of the fixed charge layer immediately above the storage portion 11 is adjusted so as to satisfy the following formula (1).
- N is the refractive index of the fixed charge layer
- K is an arbitrary integer that is 0 or more.
- the thickness of the fixed charge layer is allowed to be a value within the range (for example, ⁇ 25%).
- the light that passes through the color filter includes red and blue in addition to green. Therefore, it is more preferable to adjust the thickness of the fixed charge layer so that reflection of red and blue light is also suppressed. Further, when the thickness of the fixed charge layer is increased, light absorption in the fixed charge layer increases. Therefore, it is more preferable to make the fixed charge layer as thin as possible.
- each example described so far is such that a fixed charge layer is provided only on the second substrate surface 102 of the substrate 10. May be provided only on the first substrate surface 101, or on both the first substrate surface 101 and the second substrate surface 102.
- the conductivity type and charge polarity of the semiconductor constituting the solid-state imaging device 1 may be the reverse of the structure of each example described so far (see FIGS. 1 to 13).
- the substrate 10 may be formed of an n-type semiconductor
- the storage unit 11 may be formed of a p-type semiconductor, and may store holes generated by photoelectric conversion.
- the solid-state imaging device according to the present invention can be suitably used for, for example, a CMOS image sensor or a CCD image sensor mounted on various electronic devices having an imaging function.
- SYMBOLS 1 Solid-state image sensor 10: Board
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Abstract
Description
前記画素領域毎に前記基板中に形成され、前記基板とは逆の導電型の半導体から成るとともに光電変換によって生じた第1極性の電荷を蓄積する複数の蓄積部と、
少なくとも一方の基板表面の上方に設けられるとともに、第1固定電荷を有する固定電荷層と、を備え、
前記基板表面における前記第1固定電荷とは逆極性となる集積電荷の密度が、前記基板表面に平行な方向に対して、前記画素領域の配列または前記蓄積部の配列に対応して変化していることを特徴とする固体撮像素子を提供する。
少なくとも前記第1極性の電荷を前記蓄積部に蓄積する期間中に、前記電極層に前記第1固定電荷と同じ極性の電圧が印加されると、好ましい。
前記第1基板表面の反対側の第2基板表面から、前記基板内に光が入射するとともに、当該光の光電変換によって生じる前記第1極性の電荷を、前記蓄積部が蓄積するものであり、
少なくとも前記第2基板表面の上方に、前記固定電荷層が設けられると、好ましい。
酸化ハフニウム、酸化アルミニウム、酸化ジルコニウム、酸化タンタル、酸化チタン、酸化タングステン、酸化亜鉛、酸化イットリウム、ランタノイドの酸化物、酸化シリコン、酸化ニッケル、酸化コバルト及び酸化銅の少なくとも一つを含むと、好ましい。
前記固定電荷層の、前記蓄積部の直上となる領域の中心の膜厚が、
0.75×{500/(4×N)+K×500/(2×N)}nm以上、かつ、
1.25×{560/(4×N)+K×560/(2×N)}nm以下になるようにすると、好ましい。
最初に、本発明の実施形態に係る固体撮像素子の全体構造の一例について、図面を参照して説明する。図1は、本発明の実施形態に係る固体撮像素子の全体構造の一例を示す断面図である。なお、本願の図面は、図示の明確化のために、断面を示すハッチングを省略している。
以下、本発明の実施形態に係る固体撮像素子1において、上記のように集積電荷の密度の分布に応じた電界によって生じる暗電流を低減するための構造の具体例について、図面を参照して説明する。図2~図8は、本発明の実施形態に係る固体撮像素子における、暗電流を低減するための構造の第1~第7具体例を示す要部断面図である。なお、図2~図8では、説明の便宜上、画素領域A及び分離部18の図示を省略している。
図2を参照して、暗電流を低減するための構造の第1具体例について説明する。なお、図2中に示す太い実線の矢印は、第1具体例の構造を適用した場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図2中に示す破線の矢印は、第1具体例の構造を適用しない場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。
図3を参照して、暗電流を低減するための構造の第2具体例について説明する。なお、図3中に示す太い実線の矢印は、第2具体例の構造を適用した場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図3中に示す破線の矢印は、第2具体例の構造を適用しない場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。
図4を参照して、暗電流を低減するための構造の第3具体例について説明する。なお、図4中に示す太い実線の矢印は、第3具体例の構造を適用した場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図4中に示す破線の矢印は、第3具体例の構造を適用しない場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。
図5を参照して、暗電流を低減するための構造の第4具体例について説明する。なお、図5中に示す太い実線の矢印は、第4具体例の構造を適用した場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図5中に示す破線の矢印は、第4具体例の構造を適用しない場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。
図6を参照して、暗電流を低減するための構造の第5具体例について説明する。なお、図6中に示す太い実線の矢印は、第5具体例の構造を適用した場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図6中に示す破線の矢印は、第5具体例の構造を適用しない場合に、暗電流を成す電荷dが、再結合しない場合に辿る可能性が高い経路を示したものである。
図7を参照して、暗電流を低減するための構造の第6具体例について説明する。なお、図7中に示す太い実線の矢印は、第6具体例の構造を適用した場合に、暗電流を成す電荷dと光電変換により生じた電荷cとが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図7中に示す破線の矢印は、第6具体例の構造を適用しない場合に、暗電流を成す電荷dと光電変換により生じた電荷cとが、再結合しない場合に辿る可能性が高い経路を示したものである。
図8を参照して、暗電流を低減するための構造の第7具体例について説明する。なお、図8中に示す太い実線の矢印は、第7具体例の構造を適用した場合に、暗電流を成す電荷dと光電変換により生じた電荷cとが、再結合しない場合に辿る可能性が高い経路を示したものである。一方、図8中に示す破線の矢印は、第7具体例の構造を適用しない場合に、暗電流を成す電荷dと光電変換により生じた電荷cとが、再結合しない場合に辿る可能性が高い経路を示したものである。
[1] 第6及び第7具体例において説明した障壁部19及び誘引部20の形成方法の一例について、図面を参照して説明する。図9は、障壁部及び誘引部の形成方法の一例について説明する基板の上面図である。また、図9は、第2基板表面102側から基板10を見た場合における上面図である。
1.25×{560/(4×N)+K×560/(2×N)}nm以下 ・・・(1)
10 : 基板
101 : 第1基板表面
102 ; 第2基板表面
11 : 蓄積部
12 : 配線層
13,13e : 下地層
14,14a~14g,14p~14r : 固定電荷層
15 : 絶縁層
16 : カラーフィルタ
17 : オンチップレンズ
18 : 分離部
19 : 障壁部
20 : 誘引部
21 : 遮光層
22 : 電極層
A : 画素領域
E,H : 固定電荷
c,d,e,h : 電荷
R1,R2 : レジスト
Claims (19)
- 半導体から成り、複数の画素領域を有する基板と、
前記画素領域毎に前記基板中に形成され、前記基板とは逆の導電型の半導体から成るとともに光電変換によって生じた第1極性の電荷を蓄積する蓄積部と、
少なくとも一方の基板表面の上方に設けられるとともに、第1固定電荷を有する固定電荷層と、を備え、
前記基板表面における前記第1固定電荷とは逆極性となる集積電荷の密度が、前記基板表面に平行な方向に対して、前記画素領域の配列または前記蓄積部の配列に対応して変化していることを特徴とする固体撮像素子。 - 前記第1固定電荷の極性が前記第1極性であり、前記集積電荷の極性が前記第1極性とは逆の第2極性であることを特徴とする請求項1に記載の固体撮像素子。
- 前記基板表面における前記集積電荷の密度が、前記基板表面に平行な方向に対して、前記蓄積部に近い領域ほど高く、前記蓄積部から離れた領域ほど低いことを特徴とする請求項1または2に記載の固体撮像素子。
- 前記基板表面における前記集積電荷の密度が、前記基板表面に平行な方向に対して、前記蓄積部に近い領域ほど低く、前記蓄積部から離れた領域ほど高いことを特徴とする請求項1または2に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域における前記第1固定電荷の密度と、前記固定電荷層の前記蓄積部から離れた領域における前記第1固定電荷の密度と、が異なることを特徴とする請求項3または4に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域に施した熱処理方法と、前記固定電荷層の前記蓄積部から離れた領域に施した熱処理方法と、が異なることを特徴とする請求項5に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域における不純物の添加状態と、前記固定電荷層の前記蓄積部から離れた領域における不純物の添加状態と、が異なることを特徴とする請求項5または6に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域の膜厚と、前記固定電荷層の前記蓄積部から離れた領域の膜厚と、が異なることを特徴とする請求項3~7のいずれか1項に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域を構成する少なくとも一部の材料と、前記固定電荷層の前記蓄積部から離れた領域を構成する少なくとも一部の材料と、が異なることを特徴とする請求項3~8のいずれか1項に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域、または、前記固定電荷層の前記蓄積部から離れた領域が、前記第2極性の第2固定電荷を有することを特徴とすることを特徴とする請求項3~9のいずれか1項に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の前記蓄積部に近い領域と前記基板表面との間の距離と、前記固定電荷層の前記蓄積部から離れた領域と前記基板表面との間の距離と、が異なることを特徴とする請求項3~10のいずれか1項に記載の固体撮像素子。
- 前記基板表面と前記固定電荷層との間に設けられる、絶縁体から成る下地層を、さらに備え、
前記基板表面に平行な方向に対して、前記下地層の前記蓄積部に近い領域の膜厚と、前記下地層の前記蓄積部から離れた領域の膜厚と、が異なることを特徴とする請求項11に記載の固体撮像素子。 - 前記基板表面に平行な方向に対して、前記基板の前記蓄積部から離れた領域に、不純物濃度が周囲よりも高い障壁部が形成されることを特徴とする請求項3~12のいずれか1項に記載の固体撮像素子。
- 前記障壁部の前記基板表面側に、前記基板とは逆の導電型の半導体から成る誘引部が形成されることを特徴とする請求項13に記載の固体撮像素子。
- 前記基板表面に平行な方向に対して、前記固定電荷層の上方の前記蓄積部に近い領域、または、前記固定電荷層の上方の前記蓄積部から離れた領域に設けられる電極層を、さらに備え、
少なくとも前記第1極性の電荷を前記蓄積部に蓄積する期間中に、前記電極層に前記第1固定電荷と同じ極性の電圧が印加されることを特徴とする請求項3~14のいずれか1項に固体撮像素子。 - 前記基板中の前記画素領域の境界に、不純物濃度が周囲よりも高い分離部が形成されることを特徴とする請求項1~15のいずれか1項に記載の固体撮像素子。
- 前記基板の第1基板表面側に設けられ、前記蓄積部に蓄積される前記第1極性の電荷を制御するための配線層を、さらに備え、
前記第1基板表面の反対側の第2基板表面から、前記基板内に光が入射するとともに、当該光の光電変換によって生じる前記第1極性の電荷を、前記蓄積部が蓄積するものであり、
少なくとも前記第2基板表面の上方に、前記固定電荷層が設けられることを特徴とする請求項1~16のいずれか1項に記載の固体撮像素子。 - 前記固定電荷層が、
酸化ハフニウム、酸化アルミニウム、酸化ジルコニウム、酸化タンタル、酸化チタン、酸化タングステン、酸化亜鉛、酸化イットリウム、ランタノイドの酸化物、酸化シリコン、酸化ニッケル、酸化コバルト及び酸化銅の少なくとも一つを含むことを特徴とする請求項1~17のいずれか1項に記載の固体撮像素子。 - 前記固定電荷層の屈折率をN、0以上である任意の1つの整数をKとするとき、
前記固定電荷層の、前記蓄積部の直上となる領域の中心の膜厚が、
0.75×{500/(4×N)+K×500/(2×N)}nm以上、かつ、
1.25×{560/(4×N)+K×560/(2×N)}nm以下になることを特徴とする請求項1~18のいずれか1項に記載の固体撮像素子。
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Cited By (4)
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JP2016111253A (ja) * | 2014-12-09 | 2016-06-20 | 豊田合成株式会社 | 半導体装置およびその製造方法 |
JP2016111254A (ja) * | 2014-12-09 | 2016-06-20 | 豊田合成株式会社 | 半導体装置およびその製造方法 |
JPWO2017047422A1 (ja) * | 2015-09-17 | 2018-07-05 | ソニーセミコンダクタソリューションズ株式会社 | 固体撮像素子、電子機器、及び、固体撮像素子の製造方法 |
US10461110B2 (en) | 2013-09-27 | 2019-10-29 | Sony Corporation | Image pickup element, method of manufacturing image pickup element, and electronic apparatus |
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JP6021613B2 (ja) * | 2012-11-29 | 2016-11-09 | キヤノン株式会社 | 撮像素子、撮像装置、および、撮像システム |
JP2016021520A (ja) * | 2014-07-15 | 2016-02-04 | ソニー株式会社 | 半導体装置および電子機器 |
TWI747805B (zh) * | 2014-10-08 | 2021-12-01 | 日商索尼半導體解決方案公司 | 攝像裝置及製造方法、以及電子機器 |
JP2019212900A (ja) * | 2018-05-31 | 2019-12-12 | パナソニックIpマネジメント株式会社 | 撮像装置 |
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- 2012-11-29 TW TW101144839A patent/TWI488292B/zh not_active IP Right Cessation
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JP2008294175A (ja) * | 2007-05-24 | 2008-12-04 | Sony Corp | 固体撮像装置およびカメラ |
JP2011138905A (ja) * | 2009-12-28 | 2011-07-14 | Toshiba Corp | 固体撮像装置 |
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US10461110B2 (en) | 2013-09-27 | 2019-10-29 | Sony Corporation | Image pickup element, method of manufacturing image pickup element, and electronic apparatus |
US11557623B2 (en) | 2013-09-27 | 2023-01-17 | Sony Corporation | Image pickup element, method of manufacturing image pickup element, and electronic apparatus |
US11862652B2 (en) | 2013-09-27 | 2024-01-02 | Sony Group Corporation | Image pickup element, method of manufacturing image pickup element, and electronic apparatus |
JP2016111253A (ja) * | 2014-12-09 | 2016-06-20 | 豊田合成株式会社 | 半導体装置およびその製造方法 |
JP2016111254A (ja) * | 2014-12-09 | 2016-06-20 | 豊田合成株式会社 | 半導体装置およびその製造方法 |
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JPWO2017047422A1 (ja) * | 2015-09-17 | 2018-07-05 | ソニーセミコンダクタソリューションズ株式会社 | 固体撮像素子、電子機器、及び、固体撮像素子の製造方法 |
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TW201334168A (zh) | 2013-08-16 |
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