Patent Description:
An image sensor having a sensitivity in an infrared region, or an "infrared sensor", has been commercialized in recent years. A light-receiving device used for the infrared sensor has a photoelectric conversion layer that includes a group III-V semiconductor such as indium gallium arsenide (InGaAs). Such a photoelectric conversion layer generates electrical charges through absorption of infrared light, i.e., performs photoelectric conversion. For example, reference is made to PTL <NUM> to <NUM>.

Various proposals have been made for a device structure of a light-receiving device or an imaging device. What is, however, desired is a further improvement in efficiency of photoelectric conversion.

It is desirable to provide a light-receiving device, an imaging device, and an electronic apparatus that are able to improve efficiency of photoelectric conversion.

According to a first aspect the invention provides a light-receiving device in accordance with claim <NUM>. According to a second aspect the invention provides an electronic apparatus in accordance with claim <NUM>. According to a third aspect the invention provides an imaging device in accordance with claim <NUM>. Further aspects of the invention are set forth in the dependent claims.

An imaging device according to the invention, as defined in claim <NUM>, includes at least one pixel. The at least one pixel includes a first electrode, a second electrode, and a photoelectric conversion layer between the first electrode and the second electrode. The photoelectric conversion layer has a first section and a second section. The first section is closer to the first electrode than the second section, and the second section is closer to the second electrode than the first section. At least one of the first section and the second section have a plurality of inclined surfaces that guide incident light toward a central axis of the photoelectric conversion layer. This makes it easier for incident light to be collected inside the photoelectric conversion layer as compared with a configuration in which the first facing section and the second facing section each have a single surface.

According to the invention, it is possible to improve the efficiency of the photoelectric conversion.

The accompanying drawings are included to provide a further understanding of the technology, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and non claimed examples useful for understanding the invention and, together with the specification, serve to explain the principles of the invention.

In the following, some embodiments of the invention are described in detail with reference to the drawings. It is to be noted that description is given in the following order.

<FIG> illustrates a cross-sectional configuration of a light-receiving device, i.e., a light-receiving device <NUM>, according to an embodiment of the invention. <FIG> illustrates a planar configuration of a major part of the light-receiving device <NUM>. The light-receiving device <NUM> may be applied to a device in which a compound semiconductor is used, such as an infrared sensor. The compound semiconductor may be, for example but not limited to, a group III-V semiconductor. The light-receiving device <NUM> may include a plurality of light-receiving unit regions that are two-dimensionally disposed. The light-receiving unit region is hereinafter referred to as a "pixel P". <FIG> illustrates an example of a cross-sectional configuration of a portion corresponding to four pixels P.

The light-receiving device <NUM> may have a multilayer wiring substrate <NUM>. The light-receiving device <NUM> includes a first electrode <NUM>, a first-conductivity-type layer <NUM>, a photoelectric conversion layer <NUM>, a second-conductivity-type layer <NUM>, and a second electrode <NUM> that are provided in this order on the multilayer wiring substrate <NUM>. The first electrode <NUM>, the first-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the second-conductivity-type layer <NUM> may be provided separately for each of the pixels P. The second electrode <NUM> may be provided commonly for the plurality of pixels P.

The light-receiving device <NUM> may include a protective film <NUM> provided between the first electrode <NUM> and the multilayer wiring substrate <NUM>. The protective film <NUM> may be provided with a through electrode 21E coupled to the first electrode <NUM>. The light-receiving device <NUM> may include a passivation film <NUM>, an insulating film <NUM>, and a light-blocking film <NUM> that are provided between the mutually-adjacent pixels P. The light-receiving device <NUM> may include an on-chip lens <NUM> provided on the side on which the second electrode <NUM> is located. The on-chip lens <NUM> may be provided for each of the pixels P. The light-receiving device <NUM> may include an antireflection film <NUM> provided between the on-chip lens <NUM> and the second electrode <NUM>.

The multilayer wiring substrate <NUM> may include a substrate <NUM> and a multilayer wiring layer <NUM>. The substrate <NUM> may be, for example but not limited to, a silicon (Si) substrate. The multilayer wiring layer <NUM> may be provided between the substrate <NUM> and the protective film <NUM>. The multilayer wiring layer <NUM> may be provided with a plurality of wiring lines 12W that configure a readout integrated circuit (ROIC). The multilayer wiring layer <NUM> may be provided with a connection section 12C. The connection section 12C may be located at a position close to the protective film <NUM>, and provided for each of the pixels P. The connection section 12C may be an electrode that includes, for example but not limited to, copper (Cu). The connection section 12C may have one face that is in contact with the through electrode 21E provided in the protective film <NUM>, and that is electrically coupled to any of the wiring lines 12W. In other words, the first electrode <NUM> may be electrically coupled to the ROIC through the through electrode 21E and the connection section 12C.

The first electrode <NUM> may be an electrode, or an "anode", to which a voltage directed to reading out of signal charges generated at the photoelectric conversion layer <NUM> is supplied, and may be provided for each of the pixels P. The signal charges may be holes or electrons. In the following, the signal charges are described as being the holes for description purpose. The first electrode <NUM> may be in contact with the first-conductivity-type layer <NUM> at a substantially middle portion of the first-conductivity-type layer <NUM>, and may be so provided in a concave shape as to follow a shape of the first-conductivity-type layer <NUM>. In other words, the first electrode <NUM> may protrude toward the side on which the multilayer wiring substrate <NUM> is located. The single first electrode <NUM> may be disposed for the single pixel P. The first electrodes <NUM> of the respective mutually-adjacent pixels P may be electrically separated from each other by the protective film <NUM>.

The first electrode <NUM> may include a simple substance selected from, for example but not limited to, titanium (Ti), tungsten (W), titanium nitride (TiN), platinum (Pt), gold (Au), germanium (Ge), palladium (Pd), zinc (Zn), nickel (Ni), and aluminum (Al). Alternatively, the first electrode <NUM> may include an alloy that contains one or more of the above-described simple substances. The first electrode <NUM> may be a single film made of any of the above-described materials configuring the first electrode <NUM>, or may be a laminate film having a combination of two or more of the above-described materials. In one example, the first electrode <NUM> may be a laminate film that includes a titanium film and a tungsten film. In this example, the films may be so disposed that the titanium film is in contact with the first-conductivity-type layer <NUM>.

The first-conductivity-type layer <NUM> is provided between the first electrode <NUM> and the photoelectric conversion layer <NUM>. The first-conductivity-type layer <NUM> is in contact with the photoelectric conversion layer <NUM> such that the first-conductivity-type layer <NUM> follows along a shape of the photoelectric conversion layer <NUM>. The single first-conductivity-type layer <NUM> may be disposed for the single pixel P. The first-conductivity-type layers <NUM> of the respective mutually-adjacent pixels P may be electrically separated from each other by the passivation film <NUM> and the insulating film <NUM>. The first-conductivity-type layer <NUM> may serve as a region in which the signal charges generated at the photoelectric conversion layer <NUM> migrate, and may include a compound semiconductor that contains, for example but not limited to, a p-type impurity. In one example, the compound semiconductor that configures the first-conductivity-type layer <NUM> has a refractive index smaller than a refractive index of a compound semiconductor that configures the photoelectric conversion layer <NUM>. In one example, the first-conductivity-type layer <NUM> may include indium phosphide (InP) that contains the p-type impurity such as, but not limited to, zinc (Zn). The p-type impurity may have a concentration in a range from <NUM>×<NUM><NUM> cm-<NUM> to <NUM>×<NUM><NUM> cm-<NUM> without limitation. The first-conductivity-type layer <NUM> may have a thickness in a range from <NUM> to <NUM>,<NUM> without limitation.

<FIG> illustrates a planar shape of the first-conductivity-type layer <NUM> as viewed from the first electrode <NUM>. The first-conductivity-type layer <NUM> may have four (<NUM>) surfaces (e.g., inclined surfaces) that are in contact with the first electrode <NUM>, for example. The four (<NUM>) surfaces each may be triangular in shape without limitation, and may form respective side faces of a quadrangular pyramid having a top on the side on which the first electrode <NUM> is located. In other words, the four (<NUM>) surfaces may be so disposed as to be inclined relative to a surface of the multilayer wiring substrate <NUM>. Note that the term "quadrangular pyramid" described above is used simply for description purpose, and that a bottom surface that configures the quadrangular pyramid is not provided. In an alternative example, the first-conductivity-type layer <NUM> may have any other three-dimensional shape whose side faces are formed by the four (<NUM>) surfaces. The four (<NUM>) surfaces may be inclined at an angle of, for example but not limited to, <NUM> degrees relative to the surface of the multilayer wiring substrate <NUM>. Note that any number of surfaces of the first-conductivity-type layer <NUM> suffices as long as the first-conductivity-type layer <NUM> are in contact with the first electrode <NUM> through the plurality of surfaces. In one example, the first-conductivity-type layer <NUM> may be in contact with the first electrode <NUM> through two or more (<NUM>) surfaces. In an alternative example, the first-conductivity-type layer <NUM> may be in contact with the first electrode <NUM> through five or more surfaces. The first-conductivity-type layer <NUM> may also have four (<NUM>) surfaces through which the first-conductivity-type layer <NUM> is in contact with the photoelectric conversion layer <NUM>, for example.

The photoelectric conversion layer <NUM> may absorb light of a predetermined wavelength to thereby generate the signal charges, i.e., the electrons or the holes. According to the invention, the light of the predetermined wavelength is light of a wavelength in an infrared region. The photoelectric conversion layer <NUM> may include a compound semiconductor such as, but not limited to, a group III-V semiconductor. The single photoelectric conversion layer <NUM> may be disposed for the single pixel P. The photoelectric conversion layers <NUM> of the respective mutually-adjacent pixels P may be electrically separated from each other by the insulating film <NUM>.

The photoelectric conversion layer <NUM> provided between the first electrode <NUM> and the second electrode <NUM> may include, for example but not limited to, an i-type group III-V semiconductor. Non-limiting examples of the group III-V semiconductor used for the photoelectric conversion layer <NUM> may include indium gallium arsenide (InGaAs). A composition of the InGaAs may be, for example but not limited to, InxGa(<NUM>-x)As where x is defined as <NUM><x≦<NUM>. In one example, a value of x may be equal to or greater than <NUM> (x≧<NUM>) in order to increase a sensitivity in the infrared region. The photoelectric conversion layer <NUM> may have a thickness in a range from <NUM>,<NUM> to <NUM>,<NUM> without limitation.

<FIG> each illustrate a planar shape of the photoelectric conversion layer <NUM>. Specifically, <FIG> illustrates a planar shape of a facing section that faces the first electrode <NUM>, i.e., a first facing section (or first section) 33A, and <FIG> illustrates a planar shape of a facing section that faces the second electrode <NUM>, i.e., a second facing section 33B (or a second section). In the present embodiment, the first facing section 33A and the second facing section 33B of the photoelectric conversion layer <NUM> each have a plurality of surfaces. This configuration makes it easier for incident light to be collected inside the photoelectric conversion layer <NUM> and thereby makes it possible to improve efficiency of photoelectric conversion as described later in greater detail.

The first facing section 33A may have four (<NUM>) surfaces that are in contact with the first-conductivity-type layer <NUM>, for example. The four (<NUM>) surfaces each may be triangular in shape without limitation, and may form respective side faces of a quadrangular pyramid having a top on the side on which the first electrode <NUM> is located. In other words, the four (<NUM>) surfaces may be so disposed as to be inclined relative to the surface of the multilayer wiring substrate <NUM>. The four (<NUM>) surfaces may be inclined at an angle of, for example but not limited to, <NUM> degrees relative to the surface of the multilayer wiring substrate <NUM>. Note that the term "quadrangular pyramid" described above is used simply for description purpose, and that a bottom surface that configures the quadrangular pyramid is not provided. In an alternative example, the first facing section 33A may have any other three-dimensional shape whose side faces are formed by the four (<NUM>) surfaces. Note that any number of surfaces of the first facing section 33A suffices as long as the first facing section 33A has the plurality of surfaces. In one example, the first facing section 33A may have two or more (<NUM>) surfaces, or may have five or more surfaces.

The second facing section 33B may have four (<NUM>) surfaces that are in contact with the second-conductivity-type layer <NUM>, for example. The four (<NUM>) surfaces each may be triangular in shape without limitation, and may form respective side faces of a quadrangular pyramid having a top on the side on which the first electrode <NUM> is located. In other words, the four (<NUM>) surfaces may be so disposed as to be inclined relative to the surface of the multilayer wiring substrate <NUM>. The four (<NUM>) surfaces may be inclined at an angle of, for example but not limited to, <NUM> degrees relative to the surface of the multilayer wiring substrate <NUM>. Note that the term "quadrangular pyramid" described above is used simply for description purpose, and that a bottom surface that configures the quadrangular pyramid is not provided. In an alternative example, the second facing section 33B may have any other three-dimensional shape whose side faces are formed by the four (<NUM>) surfaces. Note that any number of surfaces of the second facing section 33B suffices as long as the second facing section 33B has the plurality of surfaces. In one example, the second facing section 33B may have two or more (<NUM>) surfaces, or may have five or more surfaces.

The second-conductivity-type layer <NUM> is provided between the photoelectric conversion layer <NUM> and the second electrode <NUM>. The second-conductivity-type layer <NUM> is in contact with the photoelectric conversion layer <NUM> such that the second-conductivity-type layer <NUM> follows along the second facing section 33B of the photoelectric conversion layer <NUM>. The single second-conductivity-type layer <NUM> may be disposed for the single pixel P. The second-conductivity-type layers <NUM> of the respective mutually-adjacent pixels P may be electrically separated from each other by the insulating film <NUM>. The second-conductivity-type layer <NUM> may serve as a region in which electrical charges discharged from the second electrode <NUM> migrate, and may include a compound semiconductor that contains, for example but not limited to, an n-type impurity. In one example, the compound semiconductor that configures the second-conductivity-type layer <NUM> has a refractive index smaller than the refractive index of the compound semiconductor that configures the photoelectric conversion layer <NUM>. In one example, the second-conductivity-type layer <NUM> may include indium phosphide (InP) that contains the n-type impurity such as, but not limited to, silicon (Si). The n-type impurity may have a concentration in a range from <NUM>×<NUM><NUM> cm-<NUM> to <NUM>×<NUM><NUM> cm-<NUM> without limitation. The second-conductivity-type layer <NUM> may have a thickness in a range from <NUM> to <NUM> without limitation.

<FIG> illustrates a planar shape of the second-conductivity-type layer <NUM> as viewed from the second electrode <NUM>. The second-conductivity-type layer <NUM> may have four (<NUM>) surfaces that are in contact with the second electrode <NUM>, for example. The four (<NUM>) surfaces each may be triangular in shape without limitation, and may form respective side faces of a quadrangular pyramid having a top on the side on which the first electrode <NUM> is located. In other words, the four (<NUM>) surfaces may be so disposed as to be inclined relative to the surface of the multilayer wiring substrate <NUM>. The four (<NUM>) surfaces may be inclined at an angle of, for example but not limited to, <NUM> degrees relative to the surface of the multilayer wiring substrate <NUM>. Note that the term "quadrangular pyramid" described above is used simply for description purpose, and that a bottom surface that configures the quadrangular pyramid is not provided. In an alternative example, the second-conductivity-type layer <NUM> may have any other three-dimensional shape whose side faces are formed by the four (<NUM>) surfaces. Note that any number of surfaces of the second-conductivity-type layer <NUM> suffices as long as the second-conductivity-type layer <NUM> is in contact with the second electrode <NUM> through the plurality of surfaces. In one example, the second-conductivity-type layer <NUM> may be in contact with the second electrode <NUM> through two or more (<NUM>) surfaces. In an alternative example, the second-conductivity-type layer <NUM> may be in contact with the second electrode <NUM> through five or more surfaces. The second-conductivity-type layer <NUM> may also have four (<NUM>) surfaces through which the second-conductivity-type layer <NUM> is in contact with the photoelectric conversion layer <NUM>, for example.

The second electrode <NUM> may serve as an electrode common to each of the pixels P, for example. The second electrode <NUM> may be so provided on the second-conductivity-type layer <NUM> (i.e., on the light-incident side) as to be in contact with the second-conductivity-type layer <NUM> at a substantially middle portion of the second-conductivity-type layer <NUM>. The second electrode <NUM> may be so provided in a concave shape as to follow a shape of the second-conductivity-type layer <NUM>. In other words, the second electrode <NUM> may protrude toward the side on which the multilayer wiring substrate <NUM> is located. The second electrode <NUM> may serve to discharge electrical charges unused as the signal charges among the electrical charges generated at the photoelectric conversion layer <NUM>, i.e., may serve as a cathode. For example, it is possible to discharge the electrons through the second electrode <NUM> in a case where the holes are to be read out from the first electrode <NUM> as the signal charges. The second electrode <NUM> may be an electrically-conductive film that allows for transmission of the incident light such as, but not limited to, infrared light. The second electrode <NUM> may include indium tin oxide (ITO), titanium-doped indium oxide (ITiO) such as In<NUM>O<NUM>-TiO<NUM>, or any other material that allows for transmission of light.

The protective film <NUM> may be so provided as to cover a surface, located on the side on which the multilayer wiring layer <NUM> is located, of the multilayer wiring substrate <NUM>. The protective film <NUM> may be made of an inorganic insulating material. Non-limiting examples of the inorganic insulating material may include silicon nitride (SiN), aluminum oxide (Al<NUM>O<NUM>), silicon oxide (SiO<NUM>), and hafnium oxide (HfO<NUM>). In one example, the protective film <NUM> may have a stacked structure including: a film that serves as an etching stopper; and any other film, as described later in greater detail. In one example, a configuration may be employed in which the silicon nitride and the silicon oxide are stacked, in consideration of the silicon nitride that serves as the etching stopper. In an alternative example, the aluminum oxide, which is high in interfacial characteristics, may be used for the protective film <NUM>. In such an alternative example, the aluminum oxide, the silicon nitride, and the silicon oxide may be stacked in this order from a position close to the first electrode <NUM>. The through electrode 21E provided in the protective film <NUM> may serve to allow the connection section 12C and the first electrode <NUM> to be coupled to each other, and may be provided for each of the pixels P. The through electrode 21E may include, for example but not limited to, copper (Cu).

The passivation film <NUM> may be provided between the protective film <NUM> and the insulating film <NUM>, and may cover a portion of a side face of the first-conductivity-type layer <NUM> provided for each of the pixels P. In other words, the passivation film <NUM> may cover the portion of the side face of the first-conductivity-type layer <NUM> which is located on the side on which the first electrode <NUM> is located. The passivation film <NUM> may include, for example but not limited to, silicon nitride. The passivation film <NUM> may have a stacked structure. The passivation film <NUM> may serve as the above-described etching stopper.

The insulating film <NUM> may cover another portion of the side surface of the first-conductivity-type layer <NUM>, i.e., may cover a portion uncovered with the passivation film <NUM> of the first-conductivity-type layer <NUM>. The insulating film <NUM> may also cover a side face of the photoelectric conversion layer <NUM> and a side face of the second-conductivity-type layer <NUM>. The insulating film <NUM> may serve to separate the mutually-adjacent photoelectric conversion layers <NUM> such that those photoelectric conversion layers <NUM> are each provided on a pixel P basis. Thus, a region between the mutually-adjacent photoelectric conversion layers <NUM> may be buried by the insulating film <NUM>. The insulating film <NUM> may include any oxide such as, but not limited to, silicon oxide (SiOx) and aluminum oxide (Al<NUM>O<NUM>). In one example, the insulating film <NUM> may have a stacked structure that includes the silicon oxide and the aluminum oxide. In such an example, the aluminum oxide may be provided at a position close to the protective film <NUM>. The insulating film <NUM> may alternatively be made of an insulating material based on silicon (Si), such as, but not limited to, silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), and silicon carbide (SiC). In one example, such a material that configures the insulating film <NUM> may be smaller in refractive index than the materials that configure the first-conductivity-type layer <NUM> and the second-conductivity-type layer <NUM>.

The light-blocking film <NUM> may be provided between the mutually-adjacent pixels P, and embedded in the insulating film <NUM>, the passivation film <NUM>, and a portion of the protective film <NUM>. Referring to <FIG>, the light-blocking film <NUM> may so extend between the pixels P as to form a wall shape, for example. This configuration prevents (or alternatively, mitigates) a migration of the signal charges between the pixels P. This configuration also prevents (or alternatively, mitigates) any adjacent pixel from being influenced by crosstalk attributed to oblique incident light.

The light-blocking film <NUM> may include a metal such as, but not limited to, titanium (Ti), tungsten (W), platinum (Pt), gold (Au), and chromium oxide (Cr<NUM>O<NUM>). Alternatively, the light-blocking film <NUM> may include an alloy of samarium (Sm) and silver (Ag), or may be made of an organic material. The light-blocking film <NUM> may be formed with use of carbon (C). The light-blocking film <NUM> may be a single film or a laminate film. In one example where the light-blocking film <NUM> is the laminate film, the light-blocking film <NUM> may be a metallic laminate film that includes, for example but not limited to, a titanium film and a tungsten film (Ti/W).

The antireflection film <NUM> may be provided on the second electrode <NUM>. For example, the antireflection film <NUM> may be provided over the entire region of the multilayer wiring substrate <NUM>. The antireflection film <NUM> may include, for example but not limited to, silicon nitride (SiN), aluminum oxide (Al<NUM>O<NUM>), silicon oxide (SiO<NUM>), or tantalum oxide (Ta<NUM>O<NUM>).

The on-chip lens <NUM> may have a function of allowing the incident light to be collected toward the photoelectric conversion layer <NUM>, and may be provided on the second electrode <NUM> with the antireflection film <NUM> in between. The on-chip lens <NUM> may be provided on an as-needed basis, and may have any shape without being limited to the shape illustrated in the drawings. In one example where the light-receiving device <NUM> detects not only the infrared light but also the visible light, the light-receiving device <NUM> may be further provided with a color filter.

The light-receiving device <NUM> may be manufactured in the following example manner. <FIG> illustrate manufacturing processes of the light-receiving device <NUM> in order of processes.

First, a substrate <NUM> may be prepared to form an oxide film <NUM> on the substrate <NUM>. The substrate <NUM> may include, for example but not limited to, silicon (Si). The oxide film <NUM> may include, for example but not limited to, silicon oxide (SiO<NUM>). It is sufficient for the oxide film <NUM> to be an insulating film that allows for selectivity for a compound semiconductor layer that is to be formed later by an epitaxial method. Non-limiting examples of such an insulating film may include carbon-containing silicon oxide (SiOC) and silicon oxynitride (SiON). Alternatively, an insulating film that includes, for example but not limited to, silicon carbide (SiC) may be used instead of the oxide film <NUM>.

Thereafter, referring to <FIG>, patterning may be performed on the thus-formed oxide film <NUM> using methods such as, but not limited to, photolithography and dry etching to thereby form an opening 52a. The plurality of openings 52a may be formed such that those openings 52a are each provided on a pixel P basis. The opening 52a may have portions a1 and a2 that are different from each other in opening width. The portion a2 may serve as an opening portion in which the photoelectric conversion layer <NUM> is to be formed in a later process. The portion at may have an aspect ratio higher than an aspect ratio of the portion a2, and may be formed inside the portion a2 as a trench, a hole, or the like. The aspect ratio of the portion at may be, for example but not limited to, <NUM> or higher. The portion a1 may extend from the portion a2 to penetrate through the oxide film <NUM>, and may be thus provided in a portion of the substrate <NUM>, i.e., a portion on the side on which the oxide film <NUM> is located.

An etching may be performed in advance on a surface of the substrate <NUM> exposed within the portion a1, using nitrohydrofluoric acid without limitation. The etching with use of the nitrohydrofluoric acid involves strong dependency on a crystal plane orientation of, for example but not limited to, a silicon substrate (in this case, the substrate <NUM>), and involves a significantly low etching rate in a (<NUM>) surface direction. Thus, the etching stops at the (<NUM>) surface for a surface on which the etching is performed, thereby forming the four (<NUM>) surfaces. The four (<NUM>) surfaces may form the side faces of the quadrangular pyramid having the top within the substrate <NUM>. In other words, the four (<NUM>) surfaces may be so disposed as to be inclined relative to a surface of the substrate <NUM>. The four (<NUM>) surfaces may be inclined at an angle of, for example but not limited to, <NUM> degrees (<NUM> degrees) relative to the surface of the substrate <NUM>. Note that the term "quadrangular pyramid" is used simply for description purpose, and that a bottom surface that configures the quadrangular pyramid is not provided.

Referring to <FIG>, after performing the etching with use of the nitrohydrofluoric acid, a buffer layer <NUM> that includes the InP without limitation may be formed from the four (<NUM>) surfaces of the substrate <NUM> to the portion at of the oxide film <NUM>, using a method such as, but not limited to, a metal organic chemical vapor deposition (MOCVD) and a molecular beam epitaxy (MBE). Growing, in this manner, the buffer layer <NUM> from the four (<NUM>) surfaces that are inclined relative to the surface of the substrate <NUM> allows for a reduction in fault density of the buffer layer <NUM>. One reason is that, upon the growth in a film-formation direction of a stacking fault that originates from an interface between the inclined (<NUM>) surfaces and the buffer layer <NUM>, the stacking fault encounters a wall of the oxide film <NUM> and thus stops its growth. An upper portion of the buffer layer <NUM> may form a shape of the quadrangular pyramid having the top on the side on which the portion a2 is located. For example, the buffer layer <NUM> formed by the InP involves a slow growth rate in the (<NUM>) surface direction, thereby allowing the four (<NUM>) surfaces that form the side faces of the quadrangular pyramid to be formed in the portion a2.

Referring to <FIG>, after the formation of the buffer layer <NUM> in the portion a1, an unillustrated etching stopper layer, the second-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the first-conductivity-type layer <NUM> may be formed continuously in this order in the portion a2. The formation of such compound semiconductor layers may be performed in-situ. In one specific but non-limiting example, the compound semiconductor layers may be formed by first forming InGaAs as the etching stopper layer after the formation of the buffer layer <NUM>. The InGaAs may be formed by changing gases, and may have a thickness in a range from <NUM> to <NUM>,<NUM> without limitation. In one example, a type and a concentration of an impurity of the etching stopper layer may be brought into conformity with those of the second-conductivity-type layer <NUM> in consideration of a profile control. After the etching stopper layer is formed, the second-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the first-conductivity-type layer <NUM> may be formed in this order while sequentially changing the gases. Upon the formation, the second-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the first-conductivity-type layer <NUM> may be each formed with the four (<NUM>) surfaces in a direction of the growth of the corresponding layer. In other words, the second-conductivity-type layer <NUM> may be formed on the four (<NUM>) surfaces of the buffer layer <NUM>, the photoelectric conversion layer <NUM> may be formed on the four (<NUM>) surfaces of the second-conductivity-type layer <NUM>, and the first-conductivity-type layer <NUM> may be formed on the four (<NUM>) surfaces of the photoelectric conversion layer <NUM>. The first-conductivity-type layer <NUM> may also be formed with the four (<NUM>) surfaces in a direction of the growth of the first-conductivity-type layer <NUM>. The (<NUM>) surfaces of each of the second-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the first-conductivity-type layer <NUM> may form the side faces of the quadrangular pyramid having the top in the direction of the growth.

Referring to <FIG>, after the formation of the first-conductivity-type layer <NUM>, the passivation film <NUM> may be formed on the first-conductivity-type layer <NUM> and the oxide film <NUM>. Thereafter, an opening may be formed on the passivation film <NUM> in a region corresponding to a middle portion of the first-conductivity-type layer <NUM>, following which the first electrode <NUM> may be formed in the opening. Specifically, a film of a material configuring the first electrode <NUM> may be so formed as to allow the opening to be buried by the film, following which the patterning of the film may be performed using methods such as, but not limited to, photolithography and etching to thereby form the first electrode <NUM>.

Referring to <FIG>, the protective film <NUM> and the through electrode 21E may be formed thereafter. Specifically, the protective film <NUM> may be formed on the first electrode <NUM> and the passivation film <NUM>, following which the protective film <NUM> may be planarized using a method such as, but not limited to, chemical mechanical polishing (CMP). In one example, the protective film <NUM> may be so formed as to have the stacked structure including: the film that serves as the etching stopper; and any other film. Non-limiting examples of the film that serves as the etching stopper may include a silicon nitride film. In one example where the silicon nitride film is used for the etching stopper, the silicon nitride film may be formed first, following which a film such as, but not limited to, a silicon oxide film may be stacked on the silicon nitride film. Thereafter, a through hole may be formed on the protective film <NUM> in a region corresponding to a middle portion of the first electrode <NUM>, using methods such as, but not limited to, the photolithography and the dry etching. Thereafter, the through electrode 21E may be formed in the through hole using a method such as, but not limited to, plating. The through electrode 21E may include copper or any other conductor.

Referring to <FIG>, the through electrode 21E may be joined to the connection section 12C of the multilayer wiring substrate <NUM> using a method such as, but not limited to, Cu-Cu bonding. Thereafter, referring to <FIG>, the substrate <NUM> may be thinned by means of a polisher without limitation, following which the thus-thinned substrate <NUM> and the buffer layer <NUM> may be removed using a method such as, but not limited to, wet etching. Alternatively, the substrate <NUM> and the buffer layer <NUM> may be removed in stages by, for example but not limited to, changing chemicals.

Referring to <FIG>, the oxide film <NUM> may be removed after the removal of the substrate <NUM> and the buffer layer <NUM>. Upon the removal of the oxide film <NUM>, a chemical having a high etching rate selectivity for the oxide film <NUM> relative to the passivation film <NUM>, the first-conductivity-type layer <NUM>, the photoelectric conversion layer <NUM>, and the second-conductivity-type layer <NUM> may be used to allow for a selective removal of only the oxide film <NUM>.

Referring to <FIG>, the insulating film <NUM> and the light-blocking film <NUM> may be thereafter formed in this order. The insulating film <NUM> may be planarized in advance using a method such as, but not limited to, the CMP. Thereafter, an opening may be formed on the insulating film <NUM> in a region corresponding to a middle portion of the second-conductivity-type layer <NUM>. The opening may be formed using methods such as, but not limited to, the photolithography and the dry etching. Alternatively, wet etching may be used instead of the dry etching. Thereafter, referring to <FIG>, the second electrode <NUM> may be formed on the opening and the insulating film <NUM>. Thereafter, an unillustrated contact structure may be formed in a region that surrounds the pixels P. The contact structure may couple the second electrode <NUM> and the multilayer wiring substrate <NUM>.

Lastly, the antireflection film <NUM> and the on-chip lens <NUM> may be formed to complete the light-receiving device <NUM> illustrated by way of example in <FIG>.

In the light-receiving device <NUM>, light having entered the photoelectric conversion layer <NUM> through the on-chip lens <NUM>, the antireflection film <NUM>, the second electrode <NUM>, and the second-conductivity-type layer <NUM> may be absorbed by the photoelectric conversion layer <NUM>. According to the invention, the light is the light of the wavelength in the infrared region. The absorption of the light generates a pair of hole and electron in the photoelectric conversion layer <NUM>, i.e., causes the photoelectric conversion of the light. In this state, a potential gradient may be generated in the photoelectric conversion layer <NUM> when a predetermined voltage is applied to the first electrode <NUM> without limitation, causing one of the thus-generated electrical charges, e.g., the holes, to migrate to the first-conductivity-type layer <NUM> as the signal charges and to be collected from the first-conductivity-type layer <NUM> to the first electrode <NUM>. The thus-collected signal charges may be read out by the ROIC of the multilayer wiring substrate <NUM>.

The light-receiving device <NUM> according to the present embodiment includes the photoelectric conversion layer <NUM> having the first facing section and the second facing section. The first facing section and the second facing section each may have the four (<NUM>) surfaces that are inclined relative to the surface of the multilayer wiring substrate <NUM>. Further, the first-conductivity-type layer <NUM> may have the four (<NUM>) surfaces through which the first-conductivity-type layer <NUM> is in contact with the first electrode <NUM>, and the second-conductivity-type layer <NUM> may have the four (<NUM>) surfaces through which the second-conductivity-type layer <NUM> is in contact with the second electrode <NUM>. The four (<NUM>) surfaces of the first-conductivity-type layer <NUM> and the four (<NUM>) surfaces of the second-conductivity-type layer <NUM> may also be inclined relative to the surface of the multilayer wiring substrate <NUM>. This makes it easier for the incident light such as the infrared light to be collected inside the photoelectric conversion layer <NUM> and thereby makes it possible to improve the efficiency of the photoelectric conversion as described below.

<FIG> and <FIG> each illustrate a process of a method of manufacturing a light-receiving device, i.e., a later-described light-receiving device <NUM> illustrated in <FIG>, according to a comparative example that is not claimed but it is useful for understanding the invention. Referring to <FIG>, a formation of the light-receiving device according to the comparative example involves, for example, performing the CMP after a photoelectric conversion layer 133A is formed. Thereafter, a first-conductivity-type layer 132A is stacked on a surface of the thus-planarized photoelectric conversion layer 133A. Referring to <FIG>, the formation of the light-receiving device according to the comparative example further involves performing the CMP on the photoelectric conversion layer 133A after the buffer layer <NUM> is formed, and forming a second-conductivity-type layer 134A on a surface of the thus-planarized photoelectric conversion layer 133A.

<FIG> illustrates a cross-sectional configuration of the light-receiving device, i.e., the light-receiving device <NUM>, manufactured through the processes illustrated in <FIG> and <FIG>. The light-receiving device <NUM> has an interface between the second electrode <NUM> and the second-conductivity-type layer 134A and an interface between the second-conductivity-type layer 134A and the photoelectric conversion layer 133A. These interfaces are parallel to the surface of the multilayer wiring substrate <NUM> to allow the light to enter. Hence, the light-receiving device <NUM> involves both a large variation in refractive index and easier reflection of the light between the second electrode <NUM> and the second-conductivity-type layer 134A and between the second-conductivity-type layer 134A and the photoelectric conversion layer 133A.

Further, an interface between the photoelectric conversion layer 133A and the first-conductivity-type layer 132A and an interface between the first-conductivity-type layer 132A and the first electrode <NUM> are parallel to the surface of the multilayer wiring substrate <NUM> as well. For such a light-receiving device <NUM>, it is necessary to sufficiently increase a thickness of the photoelectric conversion layer 133A, in that the light may not be collected sufficiently inside the photoelectric conversion layer 133A if the thickness of the photoelectric conversion layer 133A is not large enough. The photoelectric conversion layer 133A with smaller thickness may possibly result in easier generation of a dark current as well in a case where the InGaAs, which is small in band gap, is used for the photoelectric conversion layer 133A. Accordingly, it is difficult for the light-receiving device <NUM> to allow the incident light to be collected inside the photoelectric conversion layer 133A efficiently.

Moreover, the second-conductivity-type layer 134A is in contact with the second electrode <NUM> through only a single surface. The first-conductivity-type layer 132A is also in contact with the first electrode <NUM> through only a single surface. Accordingly, it is difficult for the light-receiving device <NUM> to ensure enough contact area.

In addition, methods including the CMP and the dry etching are utilized to planarize the photoelectric conversion layer 133A. Accordingly, the light-receiving device <NUM> may possibly involve a crystal defect upon the planarization process.

In contrast, referring to <FIG>, an interface between the second electrode <NUM> and the second-conductivity-type layer <NUM> and an interface between the second-conductivity-type layer <NUM> and the photoelectric conversion layer <NUM> may be inclined relative to the surface of the multilayer wiring substrate <NUM> in the light-receiving device <NUM> according to the present embodiment. Thus, the light-receiving device <NUM> allows the variation in refractive index to be moderate between the second electrode <NUM> and the second-conductivity-type layer <NUM> and between the second-conductivity-type layer <NUM> and the photoelectric conversion layer <NUM> and makes the reflection of the incident light difficult to occur accordingly, thereby allowing the light to enter the inside of the photoelectric conversion layer <NUM> easily.

Further, an interface between the photoelectric conversion layer <NUM> and the first-conductivity-type layer <NUM> and an interface between the first-conductivity-type layer <NUM> and the first electrode <NUM> may also be inclined relative to the surface of the multilayer wiring substrate <NUM>. Referring to <FIG>, this configuration allows the light that has entered the interface between the photoelectric conversion layer <NUM> and the first-conductivity-type layer <NUM> to be diffracted to the photoelectric conversion layer <NUM> that is higher in refractive index than the first-conductivity-type layer <NUM>, in a case where the refractive index of the first-conductivity-type layer <NUM> is smaller than the refractive index of the photoelectric conversion layer <NUM>. In addition, this configuration allows the light that has entered an interface between the photoelectric conversion layer <NUM> and the insulating film <NUM> to be reflected to the photoelectric conversion layer <NUM> in a case where the refractive index of the insulating film <NUM> is smaller than the refractive index of the photoelectric conversion layer <NUM>. Hence, it is possible to ensure enough optical path length and allow the light to be collected inside the photoelectric conversion layer <NUM> efficiently even for the photoelectric conversion layer <NUM> that is small in thickness. It is also possible to make the thickness of the photoelectric conversion layer <NUM> small even in a case where the InGaAs, which is small in band gap, is used for the photoelectric conversion layer <NUM>.

Accordingly, in the light-receiving device <NUM> according to the present embodiment, the four (<NUM>) surfaces may be provided for each of the first-conductivity-type layer <NUM>, the first and the second facing sections of the photoelectric conversion layer <NUM>, and the second-conductivity-type layer <NUM>. The (<NUM>) surfaces of each of them may be inclined relative to the surface of the multilayer wiring substrate <NUM>. This makes it easier for the incident light to be collected inside the photoelectric conversion layer <NUM>. Hence, it is possible to improve the efficiency of the photoelectric conversion.

Moreover, the second-conductivity-type layer <NUM> may be in contact with the second electrode <NUM> through the four (<NUM>) surfaces, and the first-conductivity-type layer <NUM> may also be in contact with the first electrode <NUM> through the four (<NUM>) surfaces. This increases the contact area as compared with the light-receiving device <NUM>. Hence, it is possible to reduce a contact resistance and improve transfer characteristics accordingly.

In addition, the light-receiving device <NUM> eliminates the necessity to provide the process of planarizing the photoelectric conversion layer <NUM>. Hence, it is possible to suppress the generation of the crystal defect.

Furthermore, in the light-receiving device <NUM>, the photoelectric conversion layer <NUM> may be formed in the opening 52a, provided for each of the pixels P, of the oxide film <NUM> to allow the pixels P to be separated from each other as illustrated in <FIG>. Hence, it is possible to suppress generation of a defect that may possibly occur upon a process of a pixel separation as described below.

In a case where InGaAs is used for a photoelectric conversion layer, a method may be contemplated in which an impurity region is selectively formed by means of, for example, an ion implantation or a selective diffusion of zinc (Zn) or the like to separate pixels. Another method may be to form an opening on an InP substrate by means of dry etching and cause an epitaxial growth of the photoelectric conversion layer to be performed in the opening to separate the pixels, as disclosed in <CIT>. However, doping an impurity in a compound semiconductor such as the InGaAs by means of the ion implantation involves a broad p-n junction profile easily, thereby possibly reducing a sensitivity. Doping the impurity may also involve easier generation of a defect resulting from an insufficient activation of the impurity. Further, the method that utilizes the dry etching as described above may involve easier generation of the crystal defect resulting from damage upon processing.

In contrast, in the light-receiving device <NUM>, the photoelectric conversion layer <NUM> may be formed in the opening 52a, provided for each of the pixels P, of the oxide film <NUM> to allow the pixels P to be separated from each other. Hence, it is possible to suppress the generation of the defect that may possibly occur upon the process of the pixel separation as described above.

According to the foregoing embodiment, the four (<NUM>) surfaces may be provided for each of the first-conductivity-type layer <NUM>, the first and the second facing sections of the photoelectric conversion layer <NUM>, and the second-conductivity-type layer <NUM>. This makes it easier for the incident light to be collected inside the photoelectric conversion layer <NUM>. Hence, it is possible to improve the efficiency of the photoelectric conversion.

In the following, description is given of modification examples and application examples of the foregoing embodiment. Note that the same or equivalent elements in the following description as those of the embodiment described above are denoted with the same reference numerals, and will not be described in detail.

<FIG> illustrates a cross-sectional configuration of a light-receiving device, i.e., a light-receiving device 1A, according to a first modification example. The light-receiving device 1A may have a configuration, workings, and effects that are similar to those of the light-receiving device <NUM>, with an exception that the light-receiving device 1A includes pixels P1 to P3 that are different from each other in size.

The light-receiving device 1A may include the larger pixel P1, the smaller pixel P2, and the pixel P3 that has a size between the pixel P1 and the pixel P2. In an example where the InGaAs is used for the photoelectric conversion layer <NUM> and the InP is used for the first-conductivity-type layer <NUM> and the second-conductivity-type layer <NUM>, light in a wavelength range around <NUM> to <NUM> without limitation is detectable. To perform the detection of such light, the light-receiving device 1A may be provided with the smaller pixel P2 directed to detection of visible light, the larger pixel P1 directed to detection of near-infrared light, and the pixel P3 directed to detection of light in a range therebetween, i.e., in a range from the visible light to the near-infrared light. In one example, the pixel P3 may have a shape of quadrangle whose one side may be in a range from <NUM> to <NUM> without limitation, the pixel P2 may have a shape of quadrangle whose one side may be in a range from <NUM> to <NUM> without limitation, and the pixel P1 may have a shape of quadrangle whose one side may be in a range from <NUM> to <NUM> without limitation.

The light-receiving device 1A may be formed in a manner similar to that of the light-receiving device <NUM>, with an exception that openings 52a (the portions a2) that are different from each other in size are formed on the oxide film <NUM>.

<FIG> illustrates a cross-sectional configuration of a light-receiving device, i.e., a light-receiving device 1B, according to a second modification example. The light-receiving device 1B may have a configuration, workings, and effects that are similar to those of the light-receiving device <NUM>, with an exception that the first facing section of a photoelectric conversion layer, i.e., a photoelectric conversion layer <NUM>, of the light-receiving device 1B has a single surface to allow a first-conductivity-type layer, i.e., a first-conductivity-type layer <NUM>, to be in contact with the first electrode <NUM> through the single surface. In other words, an interface between the photoelectric conversion layer <NUM> and the first-conductivity-type layer <NUM> may be flat and parallel to the surface of the multilayer wiring substrate <NUM>.

<FIG> illustrates a cross-sectional configuration of a light-receiving device, i.e., a light-receiving device 1C, according to a third modification example. The light-receiving device 1C may have a configuration, workings, and effects that are similar to those of the light-receiving device <NUM>, with an exception that the second facing section of a photoelectric conversion layer, i.e., a photoelectric conversion layer 43A, of the light-receiving device 1C has a single surface to allow a second-conductivity-type layer, i.e., a second-conductivity-type layer <NUM>, to be in contact with the second electrode <NUM> through the single surface. In other words, an interface between the photoelectric conversion layer 43A and the second-conductivity-type layer <NUM> may be flat and parallel to the surface of the multilayer wiring substrate <NUM>.

<FIG> illustrates a functional configuration of an imaging device <NUM> that uses the device structure of any of the light-receiving devices <NUM>, 1A, 1B, and 1C (hereinafter collectively referred to as the "light-receiving device <NUM>") described in the foregoing embodiment and the modification examples. The imaging device <NUM> may be, for example but not limited to, an infrared image sensor, and may include a pixel section 10P and a circuit section <NUM>, for example. The pixel section 10P may include the light-receiving device <NUM>, and the circuit section <NUM> may drive the pixel section 10P. For example, the circuit section <NUM> may include a row scanning section <NUM>, a horizontal selection section <NUM>, a column scanning section <NUM>, and a system controller <NUM>.

The pixel section 10P may include a plurality of pixels P, i.e., the plurality of light-receiving devices <NUM>, that are two-dimensionally arranged in rows and columns, for example. The pixels P may have a configuration in which, for example, a pixel driving line Lread (such as a row selecting line and a reset control line) is wired for each pixel row and a vertical signal line Lsig is wired for each pixel column. The pixel driving line Lread may transmit a drive signal directed to reading, from any pixel P, of a signal. The pixel driving line Lread may have one end coupled to corresponding one of output terminals, corresponding to the respective rows, of the row scanning section <NUM>.

The row scanning section <NUM> may include a component such as, but not limited to, a shift register and an address decoder. For example, the row scanning section <NUM> may be a pixel driver that drives the pixels P of the pixel section 10P on a row basis. Signals outputted from the respective pixels P in the pixel row scanned and selected by the row scanning section <NUM> may be supplied to the horizontal selection section <NUM> through the respective vertical signal lines Lsig. The horizontal selection section <NUM> may include components such as, but not limited to, an amplifier and a horizontal selection switch provided for each of the vertical signal lines Lsig.

The column scanning section <NUM> may include a component such as, but not limited to, a shift register and an address decoder, and may drive the horizontal selection switches of the horizontal selection section <NUM> in order while sequentially performing scanning of those horizontal selection switches. Such selection and scanning performed by the column scanning section <NUM> may allow the signals of the pixels P transmitted through the respective vertical signal lines Lsig to be sequentially outputted to a horizontal signal line <NUM>. The thus-outputted signals may be supplied to an unillustrated signal processor or the like through the horizontal signal line <NUM>.

Referring to <FIG>, the imaging device <NUM> may have a configuration in which a substrate 2A having the pixel section 10P and a substrate 2B having the circuit section <NUM> are stacked, for example. The imaging device <NUM>, however, is not limited to such a configuration. For example, the circuit section <NUM> may be provided on the same substrate as the pixel section 10P, or may be disposed in an external control IC. Alternatively, the circuit section <NUM> may be provided in any other substrate coupled by means of a cable or any other coupler.

The system controller <NUM> may receive a clock provided from outside, data that instructs an operation mode, and so forth. The system controller <NUM> may also output data such as internal information of the imaging device <NUM>. The system controller <NUM> may include a timing generator that generates various timing signals to thereby control, on the basis of the various timing signals generated by the timing generator, driving of circuits such as the row scanning section <NUM>, the horizontal selection section <NUM>, and the column scanning section <NUM>.

The imaging device <NUM> as described above is applicable to various types of electronic apparatuses such as, but not limited to, a camera that allows for imaging of an infrared region. <FIG> illustrates a schematic configuration of an electronic apparatus <NUM>, i.e., a camera, as a non-limiting example of such electronic apparatuses. The electronic apparatus <NUM> may be a camera that allows for shooting of a still image, a moving image, or both, for example. The electronic apparatus <NUM> may include the imaging device <NUM>, an optical system (e.g., an optical lens) <NUM>, a shutter unit <NUM>, a driver <NUM>, and a signal processor <NUM>. The driver <NUM> may drive the shutter unit <NUM>.

The optical system <NUM> may guide image light (i.e., incident light) obtained from an object to the imaging device <NUM>. The optical system <NUM> may include a plurality of optical lenses. The shutter unit <NUM> may control a period in which the imaging device <NUM> is irradiated with the light and a period in which the light is blocked. The driver <NUM> may control a transfer operation of the imaging device <NUM> and a shutter operation of the shutter unit <NUM>. The signal processor <NUM> may perform various signal processes on the signal outputted from the imaging device <NUM>. A picture signal Dout having been subjected to the signal processes may be stored in a storage medium such as a memory, or outputted to a unit such as a monitor.

The light-receiving device <NUM> described by referring to the foregoing embodiment, the modification examples, and the application examples is also applicable to the following non-limiting electronic apparatuses, including a capsule endoscope and a mobile body. The mobile body may be, for example but not limited to, a vehicle.

The technique according to any of the foregoing embodiment, the modification examples, and the application examples of the disclosure is applicable to various products. For example, the technique according to any of the foregoing embodiment, the modification examples, and the application examples of the disclosure may be applied to an endoscopic surgery system.

<FIG> is a view depicting an example of a schematic configuration of an endoscopic surgery system to which an embodiment of the invention can be applied.

In <FIG>, a state is illustrated in which a surgeon (medical doctor) <NUM> is using an endoscopic surgery system <NUM> to perform surgery for a patient <NUM> on a patient bed <NUM>. As depicted, the endoscopic surgery system <NUM> includes an endoscope <NUM>, other surgical tools <NUM> such as a pneumoperitoneum tube <NUM> and an energy treatment tool <NUM>, a supporting arm apparatus <NUM> which supports the endoscope <NUM> thereon, and a cart <NUM> on which various apparatus for endoscopic surgery are mounted.

The endoscope <NUM> includes a lens barrel <NUM> having a region of a predetermined length from a distal end thereof to be inserted into a body lumen of the patient <NUM>, and a camera head <NUM> connected to a proximal end of the lens barrel <NUM>. In the example depicted, the endoscope <NUM> is depicted which includes as a hard mirror having the lens barrel <NUM> of the hard type. However, the endoscope <NUM> may otherwise be included as a soft mirror having the lens barrel <NUM> of the soft type.

The lens barrel <NUM> has, at a distal end thereof, an opening in which an objective lens is fitted. A light source apparatus <NUM> is connected to the endoscope <NUM> such that light generated by the light source apparatus <NUM> is introduced to a distal end of the lens barrel <NUM> by a light guide extending in the inside of the lens barrel <NUM> and is irradiated toward an observation target in a body lumen of the patient <NUM> through the objective lens. It is to be noted that the endoscope <NUM> may be a direct view mirror or may be a perspective view mirror or a side view mirror.

An optical system and an image pickup element are provided in the inside of the camera head <NUM> such that reflected light (observation light) from the observation target is condensed on the image pickup element by the optical system. The observation light is photo-electrically converted by the image pickup element to generate an electric signal corresponding to the observation light, namely, an image signal corresponding to an observation image. The image signal is transmitted as RAW data to a CCU <NUM>.

The CCU <NUM> includes a central processing unit (CPU), a graphics processing unit (GPU) or the like and integrally controls operation of the endoscope <NUM> and a display apparatus <NUM>. Further, the CCU <NUM> receives an image signal from the camera head <NUM> and performs, for the image signal, various image processes for displaying an image based on the image signal such as, for example, a development process (demosaic process).

The display apparatus <NUM> displays thereon an image based on an image signal, for which the image processes have been performed by the CCU <NUM>, under the control of the CCU <NUM>.

The light source apparatus <NUM> includes a light source such as, for example, a light emitting diode (LED) and supplies irradiation light upon imaging of a surgical region to the endoscope <NUM>.

An inputting apparatus <NUM> is an input interface for the endoscopic surgery system <NUM>. A user can perform inputting of various kinds of information or instruction inputting to the endoscopic surgery system <NUM> through the inputting apparatus <NUM>. For example, the user would input an instruction or a like to change an image pickup condition (type of irradiation light, magnification, focal distance or the like) by the endoscope <NUM>.

A treatment tool controlling apparatus <NUM> controls driving of the energy treatment tool <NUM> for cautery or incision of a tissue, sealing of a blood vessel or the like. A pneumoperitoneum apparatus <NUM> feeds gas into a body lumen of the patient <NUM> through the pneumoperitoneum tube <NUM> to inflate the body lumen in order to secure the field of view of the endoscope <NUM> and secure the working space for the surgeon. A recorder <NUM> is an apparatus capable of recording various kinds of information relating to surgery. A printer <NUM> is an apparatus capable of printing various kinds of information relating to surgery in various forms such as a text, an image or a graph.

It is to be noted that the light source apparatus <NUM> which supplies irradiation light when a surgical region is to be imaged to the endoscope <NUM> may include a white light source which includes, for example, an LED, a laser light source or a combination of them. Where a white light source includes a combination of red, green, and blue (RGB) laser light sources, since the output intensity and the output timing can be controlled with a high degree of accuracy for each color (each wavelength), adjustment of the white balance of a picked up image can be performed by the light source apparatus <NUM>. Further, in this case, if laser beams from the respective RGB laser light sources are irradiated time-divisionally on an observation target and driving of the image pickup elements of the camera head <NUM> are controlled in synchronism with the irradiation timings. Then images individually corresponding to the R, G and B colors can be also picked up time-divisionally. According to this method, a color image can be obtained even if color filters are not provided for the image pickup element.

Further, the light source apparatus <NUM> may be controlled such that the intensity of light to be outputted is changed for each predetermined time. By controlling driving of the image pickup element of the camera head <NUM> in synchronism with the timing of the change of the intensity of light to acquire images time-divisionally and synthesizing the images, an image of a high dynamic range free from underexposed blocked up shadows and overexposed highlights can be created.

Further, the light source apparatus <NUM> may be configured to supply light of a predetermined wavelength band ready for special light observation. In special light observation, for example, by utilizing the wavelength dependency of absorption of light in a body tissue to irradiate light of a narrow band in comparison with irradiation light upon ordinary observation (namely, white light), narrow band observation (narrow band imaging) of imaging a predetermined tissue such as a blood vessel of a superficial portion of the mucous membrane or the like in a high contrast is performed. Alternatively, in special light observation, fluorescent observation for obtaining an image from fluorescent light generated by irradiation of excitation light may be performed. In fluorescent observation, it is possible to perform observation of fluorescent light from a body tissue by irradiating excitation light on the body tissue (autofluorescence observation) or to obtain a fluorescent light image by locally injecting a reagent such as indocyanine green (ICG) into a body tissue and irradiating excitation light corresponding to a fluorescent light wavelength of the reagent upon the body tissue. The light source apparatus <NUM> can be configured to supply such narrow-band light and/ or excitation light suitable for special light observation as described above.

<FIG> is a block diagram depicting an example of a functional configuration of the camera head <NUM> and the CCU <NUM> depicted in <FIG>.

The camera head <NUM> includes a lens unit <NUM>, an image pickup unit <NUM>, a driving unit <NUM>, a communication unit <NUM> and a camera head controlling unit <NUM>. The CCU <NUM> includes a communication unit <NUM>, an image processing unit <NUM> and a control unit <NUM>. The camera head <NUM> and the CCU <NUM> are connected for communication to each other by a transmission cable <NUM>.

The lens unit <NUM> is an optical system, provided at a connecting location to the lens barrel <NUM>. Observation light taken in from a distal end of the lens barrel <NUM> is guided to the camera head <NUM> and introduced into the lens unit <NUM>. The lens unit <NUM> includes a combination of a plurality of lenses including a zoom lens and a focusing lens.

The number of image pickup elements which is included by the image pickup unit <NUM> may be one (single-plate type) or a plural number (multi-plate type). Where the image pickup unit <NUM> is configured as that of the multi-plate type, for example, image signals corresponding to respective R, G and B are generated by the image pickup elements, and the image signals may be synthesized to obtain a color image. The image pickup unit <NUM> may also be configured so as to have a pair of image pickup elements for acquiring respective image signals for the right eye and the left eye ready for three dimensional (3D) display. If 3D display is performed, then the depth of a living body tissue in a surgical region can be comprehended more accurately by the surgeon <NUM>. It is to be noted that, where the image pickup unit <NUM> is configured as that of stereoscopic type, a plurality of systems of lens units <NUM> are provided corresponding to the individual image pickup elements.

Further, the image pickup unit <NUM> may not necessarily be provided on the camera head <NUM>. For example, the image pickup unit <NUM> may be provided immediately behind the objective lens in the inside of the lens barrel <NUM>.

The driving unit <NUM> includes an actuator and moves the zoom lens and the focusing lens of the lens unit <NUM> by a predetermined distance along an optical axis under the control of the camera head controlling unit <NUM>. Consequently, the magnification and the focal point of a picked up image by the image pickup unit <NUM> can be adjusted suitably.

The communication unit <NUM> includes a communication apparatus for transmitting and receiving various kinds of information to and from the CCU <NUM>. The communication unit <NUM> transmits an image signal acquired from the image pickup unit <NUM> as RAW data to the CCU <NUM> through the transmission cable <NUM>.

In addition, the communication unit <NUM> receives a control signal for controlling driving of the camera head <NUM> from the CCU <NUM> and supplies the control signal to the camera head controlling unit <NUM>. The control signal includes information relating to image pickup conditions such as, for example, information that a frame rate of a picked up image is designated, information that an exposure value upon image picking up is designated and/or information that a magnification and a focal point of a picked up image are designated.

It is to be noted that the image pickup conditions such as the frame rate, exposure value, magnification or focal point may be designated by the user or may be set automatically by the control unit <NUM> of the CCU <NUM> on the basis of an acquired image signal. In the latter case, an auto exposure (AE) function, an auto focus (AF) function and an auto white balance (AWB) function are incorporated in the endoscope <NUM>.

The camera head controlling unit <NUM> controls driving of the camera head <NUM> on the basis of a control signal from the CCU <NUM> received through the communication unit <NUM>.

The communication unit <NUM> includes a communication apparatus for transmitting and receiving various kinds of information to and from the camera head <NUM>. The communication unit <NUM> receives an image signal transmitted thereto from the camera head <NUM> through the transmission cable <NUM>.

Further, the communication unit <NUM> transmits a control signal for controlling driving of the camera head <NUM> to the camera head <NUM>. The image signal and the control signal can be transmitted by electrical communication, optical communication or the like.

The image processing unit <NUM> performs various image processes for an image signal in the form of RAW data transmitted thereto from the camera head <NUM>.

The control unit <NUM> performs various kinds of control relating to image picking up of a surgical region or the like by the endoscope <NUM> and display of a picked up image obtained by image picking up of the surgical region or the like. For example, the control unit <NUM> creates a control signal for controlling driving of the camera head <NUM>.

Further, the control unit <NUM> controls, on the basis of an image signal for which image processes have been performed by the image processing unit <NUM>, the display apparatus <NUM> to display a picked up image in which the surgical region or the like is imaged. Thereupon, the control unit <NUM> may recognize various objects in the picked up image using various image recognition technologies. For example, the control unit <NUM> can recognize a surgical tool such as forceps, a particular living body region, bleeding, mist when the energy treatment tool <NUM> is used and so forth by detecting the shape, color and so forth of edges of objects included in a picked up image. The control unit <NUM> may cause, when it controls the display apparatus <NUM> to display a picked up image, various kinds of surgery supporting information to be displayed in an overlapping manner with an image of the surgical region using a result of the recognition. Where surgery supporting information is displayed in an overlapping manner and presented to the surgeon <NUM>, the burden on the surgeon <NUM> can be reduced and the surgeon <NUM> can proceed with the surgery with certainty.

The transmission cable <NUM> which connects the camera head <NUM> and the CCU <NUM> to each other is an electric signal cable ready for communication of an electric signal, an optical fiber ready for optical communication or a composite cable ready for both of electrical and optical communications.

Here, while, in the example depicted, communication is performed by wired communication using the transmission cable <NUM>, the communication between the camera head <NUM> and the CCU <NUM> may be performed by wireless communication.

In the foregoing, the description has been given of one example of the endoscopic surgery system to which an embodiment of the present invention can be applied. The embodiment of the present invention may be applied to the image pickup unit <NUM> among the components of the configuration described above. Applying the embodiment of the present invention to the image pickup unit <NUM> makes it possible to obtain a clearer image of the surgical region. Hence, it is possible for the surgeon to confirm the surgical region with certainty.

Note that the description has been given above of the endoscopic surgery system as one example. The present invention may be applied to any medical system besides the endoscopic surgery system, such as, but not limited to, a micrographic surgery system.

The present invention is applicable to various products. For example, the present invention may be achieved in the form of an apparatus to be mounted to a mobile body of any kind. Non-limiting examples of the mobile body may include an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, an unmanned aerial vehicle (drone), a vessel, and a robot.

The vehicle control system <NUM> includes a plurality of electronic control units connected to each other via a communication network <NUM>. In the example depicted in <FIG>, the vehicle control system <NUM> includes a driving system control unit <NUM>, a body system control unit <NUM>, an outside-vehicle information detecting unit <NUM>, an in-vehicle information detecting unit <NUM>, and an integrated control unit <NUM>. In addition, a microcomputer <NUM>, a sound/image output section <NUM>, and a vehicle-mounted network interface (I/F) <NUM> are illustrated as a functional configuration of the integrated control unit <NUM>.

The outside-vehicle information detecting unit <NUM> detects information about the outside of the vehicle including the vehicle control system <NUM>. For example, the outside-vehicle information detecting unit <NUM> is connected with an imaging section <NUM>. The outside-vehicle information detecting unit <NUM> makes the imaging section <NUM> image an image of the outside of the vehicle, and receives the imaged image. On the basis of the received image, the outside-vehicle information detecting unit <NUM> may perform processing of detecting an object such as a human, a vehicle, an obstacle, a sign, a character on a road surface, or the like, or processing of detecting a distance thereto.

The imaging section <NUM> is an optical sensor that receives light, and which outputs an electric signal corresponding to a received light amount of the light. The imaging section <NUM> can output the electric signal as an image, or can output the electric signal as information about a measured distance. In addition, the light received by the imaging section <NUM> may be visible light, or may be invisible light such as infrared rays or the like.

In addition, the microcomputer <NUM> can output a control command to the body system control unit <NUM> on the basis of the information about the outside of the vehicle which information is obtained by the outside-vehicle information detecting unit <NUM>. For example, the microcomputer <NUM> can perform cooperative control intended to prevent (or alternatively, reduce) a glare by controlling the headlamp so as to change from a high beam to a low beam, for example, in accordance with the position of a preceding vehicle or an oncoming vehicle detected by the outside-vehicle information detecting unit <NUM>.

The sound/image output section <NUM> transmits an output signal of at least one of a sound and an image to an output device capable of visually or auditorily notifying information to an occupant of the vehicle or the outside of the vehicle. In the example of <FIG>, an audio speaker <NUM>, a display section <NUM>, and an instrument panel <NUM> are illustrated as the output device. The display section <NUM> may, for example, include at least one of an on-board display and a head-up display.

The imaging sections <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are, for example, disposed at positions on a front nose, sideview mirrors, a rear bumper, and a back door of the vehicle <NUM> as well as a position on an upper portion of a windshield within the interior of the vehicle. The imaging section <NUM> provided to the front nose and the imaging section <NUM> provided to the upper portion of the windshield within the interior of the vehicle obtain mainly an image of the front of the vehicle <NUM>. The imaging sections <NUM> and <NUM> provided to the sideview mirrors obtain mainly an image of the sides of the vehicle <NUM>. The imaging section <NUM> provided to the rear bumper or the back door obtains mainly an image of the rear of the vehicle <NUM>. The imaging section <NUM> provided to the upper portion of the windshield within the interior of the vehicle is used mainly to detect a preceding vehicle, a pedestrian, an obstacle, a signal, a traffic sign, a lane, or the like.

Incidentally, <FIG> depicts an example of photographing ranges of the imaging sections <NUM> to <NUM>. An imaging range <NUM> represents the imaging range of the imaging section <NUM> provided to the front nose. Imaging ranges <NUM> and <NUM> respectively represent the imaging ranges of the imaging sections <NUM> and <NUM> provided to the sideview mirrors. An imaging range <NUM> represents the imaging range of the imaging section <NUM> provided to the rear bumper or the back door. A bird's-eye image of the vehicle <NUM> as viewed from above is obtained by superimposing image data imaged by the imaging sections <NUM> to <NUM>, for example.

At least one of the imaging sections <NUM> to <NUM> may have a function of obtaining distance information. For example, at least one of the imaging sections <NUM> to <NUM> may be a stereo camera constituted of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

For example, the microcomputer <NUM> can determine a distance to each three-dimensional object within the imaging ranges <NUM> to <NUM> and a temporal change in the distance (relative speed with respect to the vehicle <NUM>) on the basis of the distance information obtained from the imaging sections <NUM> to <NUM>, and thereby extract, as a preceding vehicle, a nearest three-dimensional object in particular that is present on a traveling path of the vehicle <NUM> and which travels in substantially the same direction as the vehicle <NUM> at a predetermined speed (for example, equal to or more than <NUM>/hour). Further, the microcomputer <NUM> can set a following distance to be maintained in front of a preceding vehicle in advance, and perform automatic brake control (including following stop control), automatic acceleration control (including following start control), or the like. It is thus possible to perform cooperative control intended for automatic driving that makes the vehicle travel autonomously without depending on the operation of the driver or the like.

In the foregoing, the description has been given of one example of the vehicle control system to which the present invention can be applied. The present invention may be applied to the imaging section <NUM> among the components of the configuration described above. Applying the present invention to the imaging section <NUM> makes it possible to obtain a captured image which is easier to see. Hence, it is possible to reduce the fatigue of the driver.

Although the description has been given by referring to the embodiment, the modification examples, and the application examples, the contents of the disclosure are not limited to the embodiment, the modification examples, and the application examples, and may be modified in a variety of ways. For example, the layer configuration of the light-receiving device described in the foregoing embodiment is illustrative, and may further include any other layer. The materials and thicknesses of the respective layers are also illustrative and are not limited to those described above.

For example, the embodiment, the modification examples, and the application examples have been described by referring to an example in which the first electrode <NUM> and the first-conductivity-type layer <NUM> (or the first-conductivity-type layer <NUM>) are in contact with each other and the second-conductivity-type layer <NUM> (or the second-conductivity-type layer <NUM>) and the second electrode <NUM> are in contact with each other. In an alternative example, any other layer may be provided between the first electrode <NUM> and the first-conductivity-type layer <NUM> and/or between the second-conductivity-type layer <NUM> and the second electrode <NUM>.

In addition, the embodiment, the modification examples, and the application examples have been described by referring to an example in which any of the photoelectric conversion layers <NUM>, <NUM>, and 43A includes the compound semiconductor. In an alternative example, the photoelectric conversion layer <NUM> may be made of a material other than the compound semiconductor. A material configuring the photoelectric conversion layer <NUM> according to such an alternative example may be, for example but not limited to, germanium (Ge).

Further, the embodiment, the modification examples, and the application examples have been described by referring to an example in which the signal charges the holes for description purpose. In an alternative example, the signal charges may be the electrons. In such an alternative example, the first-conductivity-type layer <NUM> (or the first-conductivity-type layer <NUM>) may include the compound semiconductor that contain, for example but not limited to, the n-type impurity, and the first electrode <NUM> may serve as the cathode. In such an alternative example, the second-conductivity-type layer <NUM> (or the second-conductivity-type layer <NUM>) may include the compound semiconductor that contain, for example but not limited to, the p-type impurity, and the second electrode <NUM> may serve as the anode.

It is to be noted that the effects described in the embodiment, the modification examples, and the application examples are illustrative and non-limiting. Effects to be achieved by the disclosure may be effects that are other than those described above, or may further include other effects in addition to those described above.

Claim 1:
A light-receiving device (<NUM>) comprising at least one pixel, the at least one pixel including:
a first electrode (<NUM>);
a second electrode (<NUM>); and
a photoelectric conversion layer (<NUM>) between the first electrode (<NUM>) and the second electrode (<NUM>), the photoelectric conversion layer (<NUM>) configured to convert incident infrared light into electric charge, the photoelectric conversion layer (<NUM>) having a first section and a second section, the first section being closer to the first electrode (<NUM>) than the second section, the second section being closer to the second electrode (<NUM>) than the first section, at least one of the first section and the second section having a plurality of inclined surfaces that guide incident light toward a central axis of the photoelectric conversion layer (<NUM>), characterized by further comprising:
a first-conductivity-type layer (<NUM>) between the photoelectric conversion layer (<NUM>) and the first electrode (<NUM>), and in contact with the photoelectric conversion layer (<NUM>) along the first section of the photoelectric conversion layer (<NUM>); and
a second-conductivity-type layer (<NUM>) between the photoelectric conversion layer (<NUM>) and the second electrode (<NUM>), and in contact with the photoelectric conversion layer (<NUM>) along the second section of the photoelectric conversion layer (<NUM>),
wherein the first-conductivity-type layer (<NUM>) and the second-conductivity-type layer (<NUM>) each include a material that has a refractive index smaller than a refractive index of a material included in the photoelectric conversion layer (<NUM>).