Imaging device, imaging system, and method for manufacturing imaging device

An exemplary embodiment according to the present invention is an imaging device including a substrate in which a plurality of light receiving portions is arranged, an insulator configured to be arranged on the substrate, a plurality of first members configured to be arranged on the substrate so that each of projections of the plurality of first members on the substrate overlaps at least in part with any of the plurality of light receiving portions, and each of the plurality of first members sides is surrounded by the insulator, a second member configured to be arranged on the insulator and the plurality of first members, and a light shielding portion configured to be arranged in the second member.

BACKGROUND

1. Field of the Invention

The present invention relates to an imaging device and a method for manufacturing the imaging device.

2. Description of the Related Art

An imaging device including optical waveguides for increasing the amount of light incident on light receiving portions has recently been discussed. Japanese Patent Application Laid-Open No. 2006-261249 discusses an imaging device that includes a plurality of light receiving portions, optical waveguides for guiding light from an object to the light receiving portions, and light shielding portions for preventing incidence of light on adjacent light receiving portions.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an imaging device includes a substrate in which a plurality of light receiving portions is arranged, an insulator arranged on the substrate, a plurality of first members arranged on the substrate so that a projection of each of the plurality of first members onto the substrate at least partially overlaps with any of the plurality of light receiving portions, each of the plurality of first members being surrounded by the insulator, a second member arranged on the insulator and the plurality of first members, and a light shielding portion arranged in the second member.

According to another aspect of the present invention, an imaging device includes a substrate in which a plurality of light receiving portions is arranged, an insulator arranged on the substrate, a plurality of first members arranged on the substrate so that a projection of each of the plurality of first members onto the substrate at least partially overlaps with any of the plurality of light receiving portions, each of the plurality of first members being surrounded by the insulator, and a refractive index of the plurality of first members being higher than that of the insulator, a connection member arranged on the insulator so as to connect two adjoining first members among the plurality of first members, a refractive index of the connection member being higher than that of the insulator, and a light shielding portion arranged on the connection member.

According to yet another aspect of the present invention, a method for manufacturing an imaging device includes preparing a substrate in which a plurality of light receiving portions is arranged and on which an insulator is arranged, forming a plurality of first openings corresponding to the plurality of light receiving portions in the insulator, forming first members in the plurality of first openings respectively, forming a second member on the insulator and the plurality of first members, forming a plurality of second openings in the second member, and forming light shielding portions in the plurality of second openings respectively.

According to yet another aspect of the present invention, a method for manufacturing an imaging device includes preparing a substrate in which a plurality of light receiving portions is arranged and on which an insulator is arranged, forming a plurality of first members arranged on the substrate so that a projection of each of the plurality of first members onto the substrate at least partially overlaps with any of the plurality of light receiving portions, each of the plurality of first members being surrounded by the insulator, forming a second member arranged on the insulator and on the plurality of first members, a refractive index of the second member being lower than that of the first members, and forming a light shielding portion arranged between a first portion and a second portion of the second member, wherein a projection of the light shielding portion onto the substrate lies between projections, onto the substrate, of two adjoining first members among the plurality of first members.

DESCRIPTION OF THE EMBODIMENTS

An exemplary embodiment of the present invention is an imaging device including waveguides. More specifically, the imaging device includes a substrate in which a plurality of light receiving portions is arranged. The substrate may be a semiconductor substrate such as silicon and germanium. The light receiving portions may be photoelectric conversion units such as a photodiode.

A plurality of waveguides is arranged corresponding to the plurality of light receiving portions. The waveguides may include a conventional structure. For example, the waveguides may each include an insulator arranged on the substrate, and a first member whose sides are surrounded by the insulator and that has a refractive index higher than that of the insulator. Alternatively, the waveguides may each include an air gap or a reflecting member that is arranged between the insulator arranged on the substrate and the first member arranged with its sides surrounded by the insulator.

An exemplary embodiment is characterized by a relationship between the refractive index of a member in which light shielding portions are arranged and that of the waveguides, or a relationship between the refractive index of the member in which the light shielding portions are arranged and that of a member arranged on or under the member. For example, a second member is arranged on the waveguides. Light shielding portions are arranged in the second member. The second member may have a refractive index lower than that of the first members which constitute the waveguides. Alternatively, a third member is arranged between the second member and the waveguides. The second member may have a refractive index lower than that of the third member. Alternatively, a fourth member having a refractive index different from that of the second member may be arranged on the second member. The light shielding portions may be made of a conventional material. For example, the light shielding portions may be made of metal.

Another exemplary embodiment is an imaging device including a connection member that is arranged on the waveguides to connect adjoining waveguides. For example, the connection member is made of the same material as that of the first members which constitute the waveguides. The first members and the connection member may be formed by the same process. In such an exemplary embodiment, the light shielding portions are arranged on the connection member. The light receiving portions may be made of a conventional material. For example, the light shielding portions may be made of metal.

Japanese Patent Application Laid-Open No. 2006-261249 includes no discussion about the refractive index of the member where the light shielding portions are arranged. The imaging devices discussed in Japanese Patent Application Laid-Open No. 2006-261249 can thus cause mixing of light into the adjoining light receiving portions. In particular, in the imaging device illustrated in FIG. 2A of Japanese Patent Application Laid-Open No. 2006-261249, a high refractive index member constituting the optical waveguides is arranged on the light receiving portions. Part of the high refractive index member extends even over the light shielding portions. Since the high refractive index member arranged on the light shielding portions is not shielded from light, oblique light tends to be incident thereon. If light is incident on the high refractive index member arranged on the light shielding portions, the light can propagate through the high refractive index member and enter adjacent optical waveguides. This can cause the mixing of light into the adjoining light receiving portions.

The mixing of light into the adjoining light receiving portions can produce noise and cause a drop in image quality. According to some of the exemplary embodiments of the present invention, the mixing of light can be reduced to improve the image quality.

The exemplary embodiments of the present invention will be described in more detail below. Note that the present invention is not limited to only the exemplary embodiments described below. Modifications in which a part of the configuration of the following exemplary embodiments is modified without departing from the gist of the present invention also constitute exemplary embodiments of the present invention. Examples in which a part of the configuration of any one of the following exemplary embodiments is added to another exemplary embodiment and/or examples in which a part of the configuration of any one of the following exemplary embodiments is replaced with a part of the configuration of another exemplary embodiment also constitute exemplary embodiments of the present invention.

A first exemplary embodiment will be described. The first exemplary embodiment of the present invention will be described with reference to the drawings.FIGS. 1 and 2are schematic diagrams illustrating a cross-sectional structure and a planar layout of an imaging device according to the present exemplary embodiment, respectively.

FIG. 1illustrates three pixels arranged in a pixel area and a transistor arranged in a peripheral circuit area. In fact, the pixel area includes a plurality of pixels arranged in a matrix. The peripheral circuit area includes a plurality of transistors including ones having semiconductor regions of opposite conductivity types.

The following description deals with a case where signal charges are electrons. However, the signal charges may be holes. If the signal charges are holes, the semiconductor regions are replaced with ones of opposite conductivity types.

In the present exemplary embodiment, a semiconductor substrate101is an N-type silicon layer formed by epitaxial growth. The semiconductor substrate101includes P-type semiconductor regions and N-type semiconductor regions. The semiconductor substrate101has a main surface102. In the present exemplary embodiment, the main surface102is an interface between the semiconductor substrate101and a thermally-oxidized film (not-illustrated) stacked on the semiconductor substrate101. Light is incident on the semiconductor substrate101through the main surface102. The incident direction of the light is indicated by the arrows L.

light receiving portions103are photodiodes for example. In the present exemplary embodiment, a plurality of the light receiving portions103is arranged in the semiconductor substrate101. In the present exemplary embodiment, the light receiving portions103are N-type semiconductor regions constituting photodiodes. Charges generated by photoelectric conversion are collected to the N-type semiconductor regions. P-type semiconductor regions109are arranged in contact with the main surface102of the semiconductor substrate101.

Floating diffusions (FDs)110are N-type semiconductor regions. The charges generated by the light receiving portions103are transferred to the FDs110and converted into voltages. The FDs110are electrically connected to input nodes of a not-illustrated amplification portion. Amplification portions may be arranged for the respective pixels. Alternatively, the FDs110are electrically connected to not-illustrated signal output lines.

Gate electrodes111are arranged on the semiconductor substrate101via the not-illustrated thermally-oxidized film. The gate electrodes111arranged between the light receiving portions103and the FDs111are transfer gate electrodes for controlling transfer of charges between the light receiving portions103and the FDs110. The peripheral circuit area includes source regions119and drain regions119of the transistor.

InFIG. 1, an insulator104is arranged on the semiconductor substrate101. In the present exemplary embodiment, the insulator104is a silicon oxide film. The insulator104may have a refractive index of 1.40 to 1.60. A first wiring layer112aa second wiring layer112b, and a third wiring layer112care arranged on the semiconductor substrate101. The first wiring layer112a, the second wiring layer112b,and the third wiring layer112care located at different heights with respect to the main surface102of the semiconductor substrate101.

In the present exemplary embodiment, conductive members included in the first wiring layer112aand the second wring layer112bmainly contain copper. Conductive members included in the third wiring layer112cmainly contain aluminum. The third wiring layer112cincludes conductive members that constitute pads and a wiring layer of the peripheral circuit area. The conductive members included in each wiring layer may be made of conductive materials other than copper or aluminum. Some of the conductive members of the first wiring layer112aand some of the conductive members of the second wiring layer112bare electrically connected by not-illustrated plugs. Some of the conductive members of the second wiring layer112band some of the conductive members of the third wiring layer112care electrically connected by plugs403.

The plugs403are made of a conductive material such as tungsten. The insulator104insulates the conductive members of the first wiring layer112a, the conductive members of the second wiring layer112b, and the conductive members of the third wiring layer112cfrom each other except the portions electrically connected by the plugs. The insulator104may include a plurality of interlayer insulating films. The plurality of interlayer insulating films includes an interlayer insulating film arranged between the semiconductor substrate101and the first wiring layer112a, an interlayer insulating film arranged between the first wiring layer112aand the second wiring layer112b, and/or an interlayer insulating film arranged on the second wiring layer112b. In the present exemplary embodiment, the third wiring layer112cis located farthest from the semiconductor substrate101among the plurality of wiring layers112a,112b, and112c. Note that the number of wiring layers is not limited to three.

InFIG. 1, in the present exemplary embodiment, first members106aconstitute waveguides for guiding light. The first members106awill hereinafter be referred to as waveguide members106a. The waveguide members106aare arranged so that their sides are surrounded by the insulator104. In other words, when seen in a cross section taken along a plane parallel to the main surface102of the substrate101, the waveguide members106aare surrounded by the insulator104. A connection member106bmade of the same material as that of the waveguide members106ais arranged on the waveguide members106aand the insulator104. In the present exemplary embodiment, the waveguide members106aand the connection member106bare silicon nitride films. Alternatively, the waveguide members106aand the connection member106bmay be made of a silicon oxynitride film or an organic material (resin such as a polyimide system polymer). The waveguide members106aand the connection member106bmay be made of different materials. For example, the waveguide members106amay be a silicon nitride film, and the connection member106bmay be a silicon oxynitride film.

In the present exemplary embodiment, the waveguide members106aand the connection member106bboth have a refractive index higher than that of the insulator104. Specifically, the waveguide members106aand the connection member106bboth have a refractive index equal to or more than 1.60. Since the waveguide members106ahave a refractive index higher than that of the insulator104, light incident on the interfaces between the waveguide members106aand the insulator104is reflected based on the Snell's law. The waveguide members106acan thus confine light inside. In other words, the waveguide members106acan function as waveguides for guiding the incident light to the light receiving portions103. Silicon nitride films can be configured to have a high hydrogen content. The waveguide members106amade of silicon nitride films can thus terminate dangling bonds of the semiconductor substrate101by a hydrogen supply effect. Consequently, noise such as white defects can be reduced. Polyimide system organic materials have a refractive index of approximately 1.7. Polyimide system organic materials have embedding characteristics superior to those of silicon nitride films. With a refractive index in the range of 1.80 to 2.40, the waveguide members106acan provide improved waveguide performance.

The waveguide members106amay be configured to contain a plurality of materials. In such a case, any one of the plurality of materials may have a refractive index higher than that of the insulator104. For example, the waveguide members106amay each include a silicon nitride film and a silicon oxynitride film. The waveguide members106amay be each configured so that a silicon nitride film is arranged near the sides and bottom of the waveguide members106a, and an organic material is arranged in the other region. As illustrated inFIG. 1, the connection member106bneed not be arranged in the peripheral circuit area.

Unlike the present exemplary embodiment, waveguides may be formed by arranging an air gap or a reflecting member between the waveguide members106aand the insulator104. In such an exemplary embodiment, the refractive index of the waveguide members106ais not limited in particular. In such an exemplary embodiment, the waveguide members106amay simply be made of a light-transmitting material.

InFIG. 1, etch stop members113are arranged between the waveguide members106aand the semiconductor substrate101. The etch stop members113are layers intended to accurately stop etching when making openings for the waveguide members106ato be arranged in the insulator104. The etch stop members113may be layers for retarding the progress of the etching. The etch stop members113and the waveguide members106aare in contact with each other. The etch stop members113are formed of different material from the insulator1104. In the present exemplary embodiment, the etch stop members113are silicon nitride films. The etch stop members113may be omitted depending on the etching condition.

InFIG. 1, a second member107is arranged on the insulator104and the waveguide members106a. In the present exemplary embodiment, the second member107is a silicon oxide film. The second member107has a refractive index lower than that of the waveguide members106a. Specifically, the refractive index of the second member107falls within the range of 1.40 to 1.60.

In the present exemplary embodiment, the connection member106bis arranged between the second member107and the waveguide members106a. The connection member106has a refractive index higher than that of the second member107. That is, the connection member106bis a third member.

Another member having a refractive index higher than that of the second member107may be arranged between the connection member106band the second member107. An example of the another member is a silicon oxynitride film.

InFIG. 1, shown are light shielding portions108. In the present exemplary embodiment, at least part of the light shielding portion108is arranged in the second member107. More specifically, when seen in a cross section, each of the light shielding portions108is arranged between two portions of the second member107. The light shielding portions108are made of a metal, alloy, or organic material that does not transmit light. The material of the light shielding portions108may have a high reflectance to light having a wavelength of 400 to 600 nm. In the present exemplary embodiment, the light shielding portions108contain tungsten. The light shielding portions108may be made of the same material as that of the plugs403which electrically connect the conductive members included in the second wiring layer112bwith the conductive members included in the third wiring layers112c. If the light shielding portions108and the plugs403are made of the same material, both can be formed by the same step, which allows process simplification. In the present exemplary embodiment, the light shielding portions108and the plugs403are made of the same material and formed by the same step.

In the present exemplary embodiment, the light shielding portions108each include a first portion made of a metal or alloy, and a second portion. The second portion is arranged to reduce diffusion of the metal included in the first portion. Specifically, the second portion has a diffusion coefficient lower than that of the insulator104with respect to the diffusion of the metal included in the first portion. The second portion may be made of a barrier metal as it is called. The plugs403may also be configured to include a first portion and a second portion.

A fourth member114and first lenses115are arranged on the second member107. The fourth member114can function as a protection film. In the present exemplary embodiment, the fourth member114and the first lenses115are made of a silicon nitride film. In the present exemplary embodiment, the fourth member114and the first lenses115both have a refractive index higher than that of the second member107. Note that the fourth member114has only to have a refractive index different from that of the second member107. The fourth member114and the first lenses115need not necessarily be arranged. A planarization film116, a color filter117, and second lenses118may be arranged on the first lenses115.

The second member107may have a refractive index lower than that of the first lenses115. In the present exemplary embodiment, the silicon nitride film constituting the first lenses115has a refractive index of approximately equal to or more than 1.60. The silicon oxide film constituting the second member107has a refractive index in the range of 1.40 to 1.60. Such a relationship of the refractive indexes can improve sensitivity to obliquely incident light. The reason is as follows: Obliquely incident light may fail to be sufficiently condensed by the first lenses115, in which case the light will not be incident on the waveguide members106a.If the second member107having a refractive index lower than that of the first lenses115is arranged between the first lenses115and the waveguide members106a, the light transmitted through the first lenses115is refracted toward the waveguide members106aat the interfaces between the first lenses115and the second member107. As a result, the obliquely incident light is incident on the waveguide members106a, whereby the sensitivity to the obliquely incident light can be improved.

FIG. 10is a schematic diagram illustrating a sectional structure of another part of the imaging device according to the present exemplary embodiment. Portions having similar functions to those ofFIG. 1are designated by the same reference numerals. The pixel area according to the present exemplary embodiment includes an effective pixel area and an optical black (OB) pixel area.FIG. 10illustrates a cross section of a pixel included in the effective pixel area and a cross section of pixels included in the OB pixel area.

The optical black pixels are arranged in the OB pixel area. Specifically, a light shielding portion902is arranged over the light receiving portions103of the pixels included in the OB pixel area. The light shielding portion902shields the light receiving portions103of the pixels included in the OB pixel area from incident light. The light shielding portion902is made of the conductive material included in the third wiring layer112c. Note that the OB pixel area is provided according to need. The pixel area need not include the OB pixel area.

Next, a positional relationship between the light shielding portions108, the light shielding portion902, and the third wiring layer112caccording to the present exemplary embodiment will be described. In the present exemplary embodiment, the light shielding portions108are arranged closer to the semiconductor substrate101than the third wiring layer112cwhich is located farthest from the semiconductor substrate101among the plurality of wiring layers112ato112c.More specifically, the distance from the main surface102of the semiconductor substrate101to the bottom surfaces of the light shielding portions108is smaller than the distance from the main surface102of the semiconductor substrate101to the bottom surfaces of the conductive members included in the third wiring layer112c. The light shielding portions108are also arranged closer to the semiconductor substrate101than the light shielding portion902. More specifically, the distance from the main surface102of the semiconductor substrate101to the bottom surfaces of the light shielding portions108is smaller than the distance from the main surface102of the semiconductor substrate101to the bottom surface of the light shielding portion902. As illustrated inFIG. 10, the distance from the main surface102of the semiconductor substrate to the top surfaces of the light shielding portions108is equal to the distance from the main surface102of the semiconductor substrate101to the bottom surface of the light shielding portion902. Incidentally, the distance from the main surface102of the semiconductor substrate101to the top surfaces of the light shielding portions108may be greater than the distance from the main surface102of the semiconductor substrate101to the bottom surface of the light shielding portion902.

InFIGS. 1 and 10, the bottom surfaces of the light shielding portions108are located closer to the semiconductor substrate101than the top surface of the connection member106bis. In other words, the light shielding portions108are partly arranged in the connection member106b. However, the bottom surfaces of the light shielding portions108may be located farther from the semiconductor substrate101than the top surface of the connection member106bis. In other words, part of the second member107may be arranged between the light shielding portions108and the connection member106b.Alternatively, the bottom surfaces of the light shielding portions108may be located in the same position as that of the top surface of the connection member106b.

As illustrated inFIGS. 1 and 10, in the present exemplary embodiment, both the top surfaces of the light shielding portion108and the top surface of the second member107are in contact with the fourth member114. However, part of the second member107may be arranged between the light shielding portions108and the fourth member114. In such a case, the light shielding portions108and the second member114are not in contact with each other.

FIG. 2illustrates a planar layout diagram of the waveguide members and the light shielding portions according to the present exemplary embodiment. InFIG. 2, portions having similar functions to those ofFIG. 1are designated by the same reference numerals. A detailed description thereof will be omitted. InFIG. 2, the dotted line201represents a pixel. A pixel201includes a light receiving portion103(not illustrated inFIG. 2) and a waveguide member106a. Each light shielding portion108is arranged between two adjoining waveguide members106a. More specifically, the light shielding portion108is arranged so that a projection of the light shielding portion108on the semiconductor substrate101overlaps at least in part with a projection, on the semiconductor substrate101, of a portion of the insulator104arranged between the two adjoining first members106a.

In the present exemplary embodiment, pixels201each having a square shape are two-dimensionally arranged in a matrix as illustrated inFIG. 2. Light incident on such a group of horizontally and vertically arranged pixels includes light incident perpendicularly to the plane ofFIG. 2and obliquely incident light. The light shielding portions108are arranged in between the adjoining waveguide members106aso that the obliquely incident light passed through on chip lenses (the first lenses115) of horizontally and vertically adjoining pixels will not leak in.

The light shielding portions108may be arranged not to overlap the insulator104. For example, the light shielding portions108may be arranged on the waveguide members106aalong the outer circumferences of the waveguide members106a. Even with such an arrangement, the light shielding portions108can suppress the mixing of light into the adjoining waveguide members106a.

Next, a manufacturing method according to the present exemplary embodiment will be described with reference toFIGS. 3A,3B, and3C toFIGS. 5A and 5B. InFIGS. 3A,3B, and3C toFIGS. 5A and 5B, portions having similar functions to those ofFIGS. 1,2, and10are designated by the same reference numerals. A detailed description thereof will be omitted.

FIG. 3Aillustrates a step of preparing the semiconductor substrate101in which the plurality of light receiving portions103is arranged and on which the insulator104is arranged. More specifically, in the step illustrated inFIG. 3A, semiconductor regions are formed in the semiconductor substrate101. The gate electrodes111, the insulator104, the etch stop members113, the first wiring layer112a, and the second wiring layer112bare formed on the semiconductor substrate101.

In this step, the light receiving portions103are initially formed in the semiconductor substrate101. The gate electrodes111are formed on the semiconductor substrate101. The FDs110and the semiconductor regions119constituting a source and a drain are then formed.

Next, a protection layer301is formed on the main surface102side of the light receiving portions103. For example, the protection layer301is a silicon nitride film. The protection film301may include a plurality of layers including a silicon nitride film and a silicon oxide film. The protection layer301may have a function for reducing possible damage to the light receiving portions103in subsequent steps. The protection layer301may have an antireflection function.

The etch stop member113are formed on a side of the protection layer301opposite from the semiconductor substrate101. The etch stop members301can have a greater area than that of the bottoms of openings105to be formed later. The etch stop member301need not be formed in regions other than where the bottoms of the openings105are formed. The protection layer301and the etch stop members113need not necessarily be formed.

Next, the insulator104, the first wiring layer112a,and the second wiring layer112bare formed. In the present exemplary embodiment, the first wiring layer112aand the second wiring layer112bare formed by dual damascene method. The formation will be described by using a case where the insulator104includes a plurality of interlayer insulating films104ato104eas an example. For the sake of convenience, the plurality of interlayer insulating films104ato104ewill be referred to as first to fifth interlayer insulating films104ato104ein order from the one closet to the semiconductor substrate101.

The first interlayer insulating film104ais formed over the entire surface of the pixel area and the peripheral circuit area. A surface of the first interlayer insulating film104aon the side opposite from the semiconductor substrate101may be planarized if needed. Not-illustrated contact holes are formed in the first interlayer insulating film104a. Plugs for electrically connecting conductive members of the first wiring layer112aand semiconductor regions of the semiconductor substrate101are arranged in the contact holes.

Next, the second interlayer insulating film104bis formed on a side of the first interlayer insulating film104aopposite from the semiconductor substrate101. Portions of the second interlayer insulating film104bcorresponding to the regions where the conductive members of the first wiring layer112aare to be arranged are removed by etching. A metal film for forming the first wiring layer112ais formed on the pixel area and the peripheral circuit area. The metal film is then removed by chemical mechanical polishing (CMP) until the second interlayer insulating film104bis exposed. By such a procedure, a predetermined pattern of conductive members constituting the wiring of the first wiring layer112ais formed.

Next, the third interlayer insulating film104cand the fourth interlayer insulating film104dare formed on the pixel area and the peripheral circuit area. Portions of the fourth interlayer insulating film104dcorresponding to the regions where the conductive members of the second wiring layer112bare to be arranged are removed by etching. Next, portions of the third interlayer insulating film104ccorresponds to the regions where the plugs for electrically connecting the conductive members of the first wiring layer112aand the conductive members of the second wiring layer112bare to be arranged are removed by etching. A metal film for forming the second wiring layer112band the plugs is formed on the pixel area and the peripheral circuit area. The metal film is then removed by CMP until the fourth interlayer insulting film104dis exposed. By such a procedure, the wiring pattern of the second wiring layer112band a plug pattern are formed. Note that after the formation of the third interlayer insulating film104cand the fourth interlayer insulating film104d, portions corresponding to the regions where the plugs for electrically connecting the conductive members of the first wiring layer112aand the conductive members of the second wiring layer112bare to be arranged may be first removed by etching.

Next, the fifth interlayer insulating film104eis formed on the pixel area and the peripheral circuit area. A surface of the fifth interlayer insulating film104eon the side opposite from the semiconductor substrate101may be planarized by CMP if needed.

An etch stop film, a metal diffusion prevention film, or a film having both functions may be arranged between the interlayer insulating films104ato104e. Specifically, if the insulator104is a silicon oxide film, a silicon nitride film may be arranged as a metal diffusion prevention film.

The first wiring layer112aand the second wiring layer112bmay be formed by a technique other than the damascene method. An example of the technique other than the damascene method will be described. After the formation of the first interlayer insulating film104a, a metal film for forming the first wiring layer112ais formed on the pixel area and the peripheral circuit area. Portions of the metal film other than the regions where the conductive members of the first wiring layer112aare to be arranged are removed by etching. This forms the wiring pattern of the first wiring layer112a. Subsequently, the second interlayer insulating film104band the third interlayer insulating film104care formed, and the second wiring layer112bis formed in a similar manner. After the formation of the second wiring layer112b, the fourth interlayer insulating film104dand the fifth interlayer insulating film104eare formed. Surfaces of the third interlayer insulating film104cand the fifth interlayer insulating film104eon the side opposite from the semiconductor substrate101are planarized if needed.

FIG. 3Billustrates a step of forming a plurality of openings105in the insulator104. The plurality of openings105is formed in positions corresponding to the plurality of light receiving portions103. Initially, a not-illustrated etch mask pattern is formed on a side of the insulator104opposite from the semiconductor substrate101. The etch mask pattern is arranged in regions other than where the openings105are to be arranged. In other words, the etch mask pattern has openings in the regions where the openings105are to be arranged. An example of the etch mask pattern is a photoresist patterned by photolithography and development.

Subsequently, the insulator104is etched by using the etch mask pattern as a mask. This forms the openings105. After the etching of the insulator104, the etch mask pattern is removed.

If the etch stop members113are arranged, the etching is performed until the etch stop members113are exposed inFIG. 3B. Under an etching condition for etching the insulator104, the etch stop members113have an etching rate lower than that of the insulator104under the same condition. If the insulator104is a silicon oxide film, the etch stop members113may be a silicon nitride film or a silicon oxynitride film. The etch stop members113may be exposed by a plurality of times of etching with different conditions.

FIG. 3Cillustrates a step of forming the waveguide members106ain the respective plurality of openings105. In the present exemplary embodiment, the waveguide members106aand the connection member106bare formed in the step ofFIG. 3C. The material of the waveguide members106aand the connection member106bis deposited on the pixel area and the peripheral circuit area. This forms the waveguide members106ain the openings105, and the connection member106bon the waveguide members106aand the insulator104. An example of the material of the waveguide members106aand the connection member106bis a silicon nitride film. The material of the waveguide members106aand the connection member106bcan be deposited by film formation such as chemical vapor deposition (CVD) and sputtering, or by application of organic material such as a polyimide system polymer. After the deposition of the material of the waveguide members106aand the connection member106b, planarization may be performed by using etch back or CMP. In the present exemplary embodiment, CMP-based planarization is performed. If the insulator104is etched to expose the etch stop members113in the step ofFIG. 3B, the waveguide members106aare arranged in contact with the etch stop members113.

In the present exemplary embodiment, the material of the waveguide members106ais deposited on the insulator104arranged in the peripheral circuit area. The portion of the material arranged in the peripheral circuit area is removed after the planarization and before the formation of the second member107. Meanwhile, in the pixel area, the material of the waveguide members106ais left on the insulator104. In other words, the remaining material constitutes the connection member106b. The removal of the connection member106bfrom the peripheral circuit area facilitates the formation of openings402intended for the plugs403to be described below. Note that the material of the waveguide members106adeposited on the peripheral circuit area need not be removed. If the material is left unremoved, the connection member106bextends even to the peripheral circuit area.

Alternatively, the same material may be deposited a plurality of times to form the waveguide members106aand the connection member106b. Further, a plurality of different materials may be deposited in succession to form the waveguide members106aand the connection member106b. For example, the waveguide members106aand the connection member106bmay be formed by initially depositing a silicon nitride film and then depositing an organic material having high embedding performance.

FIG. 4Aillustrates a step of forming the second member107on the insulator104and the plurality of waveguide members106a. In the present exemplary embodiment, the second member107is formed on the connection member106b. For example, a silicon oxide film is formed by CVD. A side of the second member107opposite from the semiconductor substrate101may be planarized by CMP.

FIG. 4Billustrates a step of forming a plurality of openings401in the second member107. InFIG. 4B, the openings401are formed in regions where the light shielding portions108are to be formed. In the present exemplary embodiment, the openings402are formed in the regions where the plugs403are to be formed. The plugs403are intended to electrically connect conductive members included in the second wiring layer112band conductive members included in the third wiring layer112c. In the present exemplary embodiment, a formation method when the light shielding portions108contain tungsten will be described.

Initially, a not-illustrated etch mask pattern is formed on the second member107. The etch mask pattern is arranged in regions other than where the openings401and402are to be arranged. In other words, the etch mask pattern has openings in the regions where the openings401and402are to be arranged. An example of the etch mask pattern is a photoresist patterned by photolithography and development.

The second member107is then etched by using the etch mask pattern as a mask. This forms the openings401and402. After the etching of the second member107, the etch mask pattern is removed. In the present exemplary embodiment, the openings401and402are simultaneously formed by using the connection member106bas an etching stop during the formation of the openings401. However, the openings401and402need not necessarily be formed at the same time.

FIG. 4Cillustrates a step of forming the light shielding portions108in the respective plurality of openings401. More specifically, inFIG. 4C, the light shielding portions108, the plugs403, and the third wiring layer112care formed.

Initially, a metal film for forming the light shielding portions108and the plugs403is formed in the openings401and402and on the second member107. If the light shielding portions108include a first portion and a second portion made of a barrier metal, a barrier metal layer is formed in the openings401and402and on the second member107before the formation of the metal film. In the present exemplary embodiment, the light shielding portions108and the plugs403each include a first portion mainly containing tungsten and a second portion mainly containing titanium nitride which is a barrier metal. The metal film and the barrier metal layer are then removed except inside the openings401and402by using a method such as CMP and etch back so that the second member107, an underlayer, is exposed. In the present exemplary embodiment, the light shielding portions108and the plugs403are simultaneously formed for the sake of process simplification. However, the light shielding portions108and the plugs403need not necessarily be formed at the same time.

Next, for example, an aluminum film is formed on the pixel area and the peripheral circuit area. The aluminum film is etched to form the third wiring layer112c. Although omitted inFIG. 4C, the light shielding portion902to be arranged on the light receiving portions103of the OB pixel area may be formed in the step of forming the third wiring layer112c.

InFIG. 5A, the fourth member114and the first lenses115are formed. The fourth member114and the first lenses115are formed on a side of the second member107opposite from the semiconductor substrate101. The first lenses115are arranged corresponding to the light receiving portions103of the pixel area. The fourth member114and the first lenses115can be formed by a conventional method.

InFIG. 5B, the planarization film116, the color filter117, and the second lenses118are formed. Initially, the planarization film116is formed to cover the fourth member114and the first lenses115. The planarization film116is an insulator. For example, the planarization film116is made of a polyimide system organic material. The color filter117and the second lenses118are then formed in positions corresponding to the light receiving portions103.

As described above, in the present exemplary embodiment, the second member107having a refractive index lower than that of the waveguide members106ais arranged on the insulator104and the plurality of waveguide members106a.The light shielding portions108are arranged in the second member107. Such a configuration can reduce the propagation of oblique light through a member having a high refractive index and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the connection member106bis arranged on the insulator104and the plurality of waveguide members106a. The connection member106bis arranged to connect two adjoining waveguide members106aand has a refractive index higher than that of the insulator104. The light shielding portions108are arranged on the connection member106b. According to such a configuration, the incidence of light on the connection member106bconnecting the adjoining waveguide members106acan be reduced. This can reduce the propagation of oblique light through the connection member106and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the second member107is arranged on the insulator104and the plurality of waveguide members106a. The third member (connection member106b) having a refractive index higher than that of the second member107is arranged between the second member107and the plurality of waveguide members106a. The light shielding portions108are arranged in the second member107. According to such a configuration, the provision of the light shielding portions108in a low refractive index member arranged on a high refractive index member can reduce the incidence of light on the high refractive index member. This can reduce the propagation of oblique light through the high refractive index member and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the second member107is arranged on the insulator104and the plurality of waveguide members106a. The fourth member114having a refractive index different from that of the second member107is arranged on the second member107. The light shielding portions108are arranged in the second member117. The second member107and the light shielding portions108are both arranged in contact with the fourth member114.

According to such a configuration, the second member107is not arranged between the light shielding portions108and the fourth member114. If part of the second member107is arranged between the light shielding portions108and the fourth member114, an interface between the fourth member114and the second member107is formed above the light shielding portions108. Obliquely incident light may be refracted or reflected by such an interface and incident on the adjoining waveguide members106a. As compared to the case where part of the second member107is arranged between the light shielding portions108and the fourth member114, the mixing of light can thus be reduced. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the light shielding portions108extend from the top surface to the bottom surface of the second member107. This can further improve the effect of reducing the mixing of light.

A second exemplary embodiment will be described. The second exemplary embodiment deals with another exemplary embodiment of the present invention. The present exemplary embodiment differs from the first exemplary embodiment in the planar layout of the light shielding portions. In other respects, the present exemplary embodiment is similar to the first exemplary embodiment. The following description will deal only with differences from the first exemplary embodiment. A description of the other parts is omitted.

FIG. 6is a schematic diagram illustrating a planar layout according to an imaging device of the present exemplary embodiment.FIG. 6illustrates waveguide members106aand light shielding portions601. Portions having similar functions to those ofFIG. 2are designated by the same reference numerals. A detailed description thereof will be omitted.

In the present exemplary embodiment, each pixel201includes a light receiving portion103(not illustrated inFIG. 6) and a waveguide member106a. The light shielding portions601are each arranged between two adjoining waveguide members106a. In the present exemplary embodiment, the light shielding portions601are arranged in a lattice pattern. More specifically, the light shielding portions601are arranged so that the projections of the light shielding portions601on the semiconductor substrate101surround the projections of the waveguide members106aon the semiconductor substrate101. The light shielding portions601are arranged not only between waveguide members106aarranged to adjoin in a vertical direction or horizontal direction, but also between waveguide members106aarranged to adjoin in diagonal directions.

The OB pixel area according to the present exemplary embodiment has a cross-sectional structure similar to that of the first exemplary embodiment. In other words,FIG. 10is a schematic cross-sectional view of the OB pixel area according to the present exemplary embodiment. A manufacturing method of the present exemplary embodiment is similar to that of the first exemplary embodiment. More specifically, the imaging device of the present exemplary embodiment can be formed by the manufacturing method illustrated inFIGS. 3A,3B, and3C toFIGS. 5A and 5B.

As has been described above, in the present exemplary embodiment, the light shielding portions601are arranged in a lattice pattern. Such a configuration can further reduce the leaking of light into the adjoining light receiving portions103.

A third exemplary embodiment will be described. The third exemplary embodiment deals with another exemplary embodiment of the present invention. The present exemplary embodiment differs from the first exemplary embodiment in the manufacturing process for forming the light shielding portions and the second member. The following description will deal only with differences from the first exemplary embodiments. A description of the other parts is omitted.

A manufacturing method according to the present exemplary embodiment will be described with reference toFIGS. 7A,7B, and7C. InFIGS. 7A to 7C, portions having similar functions to those ofFIGS. 3A,3B, and3C toFIGS. 5A and 5Bare designated by the same reference numerals. A detailed description thereof will be omitted. The manufacturing method according to the present exemplary embodiment includes the steps illustrated inFIGS. 3A to 3Cof the first exemplary embodiment. The steps up toFIG. 3Care the same as in the first exemplary embodiment. A detailed description thereof will be omitted.

In the present exemplary embodiment, after the step illustrated inFIG. 3C, light shielding portions701are formed on the connection member106b. Initially, a film of the material of the light shielding portions701is formed on the pixel area and the peripheral circuit area. The film of the material of the light shielding portions701is partly etched to form the light shielding portions701arranged on the connection member106b.

Next, inFIG. 7B, a second member702is formed. The second member702is formed on a side of the light shielding portions701, the waveguide members106a, and the connection member106bopposite from the semiconductor substrate101. An example of the second member702is a silicon oxide film formed by CVD. A surface of the second member702on the side opposite from the semiconductor surface101may be planarized by CMP.

Subsequently, inFIG. 7C, the third wiring layer112c,the fourth member114, the first lenses115, the planarization film116, the color filter117, and the second lenses118are formed by the same processes as the steps of the first exemplary embodiment.

The imaging device of the present exemplary embodiment formed by the foregoing manufacturing method will be described. In the present exemplary embodiment, the light shielding portions701are arranged at least in part in the second member702. More specifically, when seen in a cross section, the light shielding portions701are each arranged sandwiched between two portions of the second member702. The light shielding portions701are made of a metal, alloy, or organic material that does not transmit light. The material of the light shielding portions701may have a high reflectance to light having a wavelength of 400 to 600 nm. In the present exemplary embodiment, the light shielding portions701contain tungsten. The light shielding portions701may be made of the same material as that of the plugs403which electrically connect conductive members included in the second wiring layer112band conductive members included in the third wiring layer112c. If the light shielding portions701and the plugs403are made of the same material, both can be formed by the same step to cause process to be simple. In the present exemplary embodiment, the light shielding portions701and the plugs403are made of the same material but formed in separate steps. The light shielding portions701are formed before the formation of the second member702. The plugs403are formed after the formation of the second member702.

In the present exemplary embodiment, the light shielding portions701each include a first portion made of a metal or alloy, and a second portion. The second portion is arranged to reduce diffusion of the metal included in the first portion. Specifically, the second portion has a diffusion coefficient lower than that of the insulator104with respect to the diffusion of the metal included in the first portion. The second portion may be made of a barrier metal, as it is called. The plugs403may also include a first portion and a second portion each. In the present exemplary embodiment, both the light shielding portions701and the plugs403include a first portion mainly containing tungsten and a second portion mainly containing titanium nitride which is a barrier metal.

As illustrated inFIG. 7C, in the present exemplary embodiment, part of the second member702is arranged between the light shielding portions701and the fourth member114.

As has been described above, in the present exemplary embodiment, the second member702having a refractive index lower than that of the waveguide members106ais arranged on the insulator104and the plurality of waveguide members106a.The light shielding portions701are arranged in the second member702. Such a configuration can reduce the propagation of oblique light through a member having a high refractive index and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the connection member106bis arranged on the insulator104and the plurality of waveguide members106a. The connection member106bis arranged to connect two adjoining waveguide members106aand has a refractive index higher than that of the insulator104. The light shielding portions701are arranged on the connection member106b. According to such a configuration, the incidence of light on the connection member106bconnecting the adjoining waveguide members106acan be reduced. This can reduce the propagation of oblique light through the connection member106band the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the second member702is arranged on the insulator104and the plurality of waveguide members106a. The third member (connection member106b) having a refractive index higher than that of the second member702is arranged between the second member702and the plurality of waveguide members106a. The light shielding portions701are arranged in the second member702. According to such a configuration, the provision of the light shielding portions701in the low refractive index member arranged on the high refractive index member can reduce the incidence of light on the high refractive index member. This can reduce the propagation of oblique light through the high refractive index member and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

A fourth exemplary embodiment will be described. The fourth exemplary embodiment deals with another exemplary embodiment of the present invention. The present exemplary embodiment differs from the first exemplary embodiment in that no connection member is arranged on the insulator104. In other respects, the present exemplary embodiment is similar to the first exemplary embodiment. The following description will deal only with differences from the first exemplary embodiment. A description of the parts similar to those of the first exemplary embodiment is omitted.

FIG. 8is a schematic diagram illustrating a cross-sectional structure of an imaging device according to the present exemplary embodiment. InFIG. 8, portions having similar functions to those ofFIG. 1are designated by the same reference numerals. A detailed description thereof will be omitted. As illustrated inFIG. 8, no member containing the same material as that of the waveguide members106ais arranged on the insulator104. The insulator104and the second member107are thus arranged in contact with each other.

In the present exemplary embodiment, the second member107is arranged on the insulator104and the plurality of waveguide members106a. The second member107has a refractive index lower than that of the waveguide members106a.The light shielding portions108are arranged at least in part in the second member107. In other words, when seen in a cross section, the light shielding portions108are each arranged between two portions of the second member107.

The fourth member114is arranged on the light shielding portions108and the second member107. The fourth member114has a refractive index different from that of the second member107. The light shielding portions108and the second member107are both arranged in contact with the fourth member114.

FIG. 11is a schematic diagram illustrating a cross-sectional structure of another part of the imaging device according to the present exemplary embodiment. Portions having similar functions to those ofFIG. 8are designated by the same reference numerals. The pixel area according to the present exemplary embodiment includes an effective pixel area and an OB pixel area.FIG. 11illustrates a cross section of a pixel included in the effective pixel area and a cross section of pixels included in the OB pixel area.

The OB pixel area includes optical black pixels. Specifically, a light shielding portion902is arranged over the light receiving portions103of the pixels included in the OB pixel area. The light shielding portion902shields the light receiving portions103of the pixels included in the OB pixel area from incident light. The light shielding portion902is made of the conductive material included in the third wiring layer112c. Note that the OB pixel area is provided according to need. The pixel area need not include the OB pixel area.

FIG. 11illustrates an example where there is arranged an etch stop film901. The etch stop film901is arranged on the insulator104between adjoining waveguide members106a.The etch stop film901and the light shielding portions108are arranged in contact with each other. The etch stop film901has both a function as a stopper when removing the material of the waveguide members106adeposited on the insulator104and a function as stopper when forming the openings401intended for the light shielding portions108in manufacturing processes to be described below. The etch stop film901is provided according to need. As illustrated inFIGS. 9A,9B, and9C, the etch stop film901may be omitted.

The light shielding portions108have a planar layout similar to that of the first or second exemplary embodiment. In other words,FIG. 2or6illustrates the planar layout of the light shielding portions108according to the present exemplary embodiment. A detailed description will be omitted.

Next, a manufacturing process according to the present exemplary embodiment will be described with reference toFIGS. 9A to 9C. InFIGS. 9A to 9C, portions having similar functions to those ofFIGS. 1 to 8orFIG. 11are designated by the same reference numerals. A detailed description thereof is omitted. A manufacturing method according to the present exemplary embodiment includes the steps illustrated inFIGS. 3A and 3Bof the first exemplary embodiment. The steps up toFIG. 3Bare similar to those of the first exemplary embodiment. A detailed description thereof will be omitted.

In the step illustrated inFIG. 9A, the waveguide members106aare formed in the respective plurality of openings105. The material of the waveguide members106ais initially deposited on the pixel area and the peripheral circuit area. As a result, the material of the waveguide members106ais deposited in the openings105and on the insulator104. An example of the material of the waveguide members106ais a silicon nitride film. The material of the waveguide members106acan be deposited by film formation such as CVD and sputtering, or by application of organic material such as a polyimide system polymer.

If the insulator104is etched to expose the etch stop members113in the step ofFIG. 3B, the waveguide members106aare arranged in contact with the etch stop member113. The same material may be deposited a plurality of times to form the waveguide members106a. A plurality of different materials may be formed in succession to form the waveguide members106a. For example, the waveguide members106amay be formed by initially depositing a silicon nitride film and then depositing an organic material having high embedding performance.

In the present exemplary embodiment, portions of the deposited film of the material of the waveguide members106aarranged on the insulator104are removed. In the first exemplary embodiment, in the step ofFIG. 3C, the material of the waveguide members106ais planarized by CMP so that the connection member106bremains. In contrast, according to the present exemplary embodiment, the material of the waveguide members106ais subjected to CMP until the underlayer is exposed. In the present exemplary embodiment, there is thus formed no connection member106b. The material of the waveguide members106amay be removed by polishing or etching.

If the material of the waveguide members106ais deposited in contact with the insulator104, the CMP is performed until the insulator104is exposed. The CMP condition for removing the material of the waveguide members106amay be such that the insulator104has a polishing rate lower than that of the material of the waveguide members106a. In other words, the insulator104may have a function as a CMP stopper.

Alternatively, if the etch stop film901is arranged as illustrated inFIG. 11, the CMP is performed until the etch stop film901is exposed. The CMP condition for removing the material of the waveguide members106amay be such that the etch stop film901has a polishing rate lower than that of the material of the waveguide members106a. In such a case, the etch stop film901functions as a CMP stopper.

In the step illustrated inFIG. 9B, the second member107, the light shielding portions108arranged in the second member107, the plugs403, and the third wiring layer112care formed on the waveguide members106a. A method for forming such components is similar to the steps ofFIGS. 4A to 4Caccording to the first exemplary embodiment or the steps ofFIGS. 7A to 7Caccording to the third exemplary embodiment. A detailed description will thus be omitted.

If the etch stop film901is arranged as illustrated inFIG. 11, the etch stomp film901may function as a stopper during the formation of the openings401. The etch stop film901thus has both functions as a CMP stopper and a stopper during the formation of the openings401.

In the step illustrated inFIG. 9C, the fourth member114, the first lenses115, the planarization film116, the color filter117, and the second lenses118are formed by a process similar to the steps of the first exemplary embodiment.

As has been described above, in the present exemplary embodiment, the second member107having a refractive index lower than that of the waveguide members106ais arranged on the insulator104and the plurality of waveguide members106a.The light shielding portions108are arranged in the second member107. Such a configuration can reduce the propagation of oblique light through a member having a high refractive index and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the connection member106bis arranged on the insulator104and the plurality of waveguide members106a. The connection member106bis arranged to connect two adjoining waveguide members106aand has a refractive index higher than that of the insulator104. The light shielding portions108are arranged on the connection member106b. According to such a configuration, the incidence of light on the connection member106bconnecting the adjoining waveguide members106acan be reduced. This can reduce the propagation of oblique light through the connection member106and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the second member107is arranged on the insulator104and the plurality of waveguide members106a. The third member (connection member106b) having a refractive index higher than that of the second member107is arranged between the second member107and the plurality of waveguide members106a. The light shielding portions108are arranged in the second member107. According to such a configuration, the provision of the light shielding portions108in a low refractive index member arranged on a high refractive index member can reduce the incidence of light on the high refractive index member. This can reduce the propagation of oblique light through the high refractive index member and the mixing of the light into the adjoining waveguide members106a. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

In the present exemplary embodiment, the second member107is arranged on the insulator104and the plurality of waveguide members106a. The fourth member114having a refractive index different from that of the second member107is arranged on the second member107. The light shielding portions108are arranged in the second member107. The second member107and the light shielding portions108are both arranged in contact with the fourth member114.

According to such a configuration, the second member107is not arranged between the light shielding portions108and the fourth member114. If part of the second member107is arranged between the light shielding portions108and the fourth member114, an interface between the fourth member114and the second member107is arranged above the light shielding portions108. Obliquely incident light may be refracted or reflected by the interface and incident on the adjoining waveguide members106a. As compared to when part of the second member107is arranged between the light shielding portions108and the fourth member114, the mixing of light can thus be reduced. As a result, the mixing of light into the adjoining light receiving portions103can be reduced.

A fifth exemplary embodiment will be described. The fifth exemplary embodiment deals with an exemplary embodiment of an imaging system according to the present invention. Examples of the imaging system include a digital still camera, a digital camcorder, a copying machine, a facsimile, a mobile phone, a car-mounted camera, and an observation satellite.FIG. 12illustrates a block diagram of a digital still camera as an example of the imaging system.

InFIG. 12, a barrier1001protects a lens1002. The lens1002forms an optical image of an object on an imaging device1004. A diaphragm1003varies the amount of light passed through the lens1002. The imaging device1004is an imaging device described in any one of the foregoing exemplary embodiments. The imaging device1004converts the optical image formed by the lens1002into image data. An analog-to-digital (AD) conversion unit is formed on the semiconductor substrate of the imaging device1004. A signal processing unit1007makes various corrections to captured data output by the imaging device1004, and performs data compression. InFIG. 12, a timing generation unit1008outputs various timing signals to the imaging device1004and the signal processing unit1007. A general control unit1009controls the entire digital still camera. A frame memory unit1010temporarily stores image data. An interface unit1011is intended to perform recording and/or reading on a recording medium1012. The recording medium1012is a detachably attached semiconductor memory for captured data to be recorded on and/or read from. An interface unit1013is intended to communicate with an external computer. The timing signals and the like may be input from outside the imaging system. The imaging system needs to include at least the imaging device1004and the signal processing unit1007which processes an imaging signal output from the imaging device1004.

In the present exemplary embodiment, the imaging device1004and the AD conversion unit are described to be formed on the same semiconductor substrate. However, the imaging device1004and the AD conversion unit may be formed on different semiconductor substrates. Further, the imaging device1004and the imaging processing unit1007may be formed on the same substrate.

In the present exemplary embodiment, the imaging device1004is any one of the imaging devices according to the first to fourth exemplary embodiments. Any one of the imaging devices according to the first to fourth exemplary embodiments can thus be applied to an imaging system. The application of the exemplary embodiments according to the present invention to the imaging system can improve image quality.

This application claims the benefit of Japanese Patent Application No. 2012-174843 filed Aug. 7, 2012, which is hereby incorporated by reference herein in its entirety.