Solid-state imaging device and camera system

A first substrate has a plurality of photoelectric conversion units. A second substrate has through vias connected to the first substrate, and a plurality of photoelectric conversion units. A third substrate has vias connected to the second substrate, and a circuit that processes a signal. Wiring lines of the first substrate select the angle of a light ray that is transmitted through the first substrate and enters the second substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device having a plurality of substrates and a camera system equipped therewith.

Priority is claimed on Japanese Patent Application No. 2012-053279, filed Mar. 9, 2012, the contents of which are incorporated herein by reference.

2. Description of Related Art

In recent years, generally, video cameras, electronic still cameras, or the like have become widely prevalent. CCD (Charge Coupled Device) type or amplified solid-state imaging devices are used for these cameras. The amplified solid-state imaging devices guide signal charges, which are generated and accumulated by photoelectric conversion units of pixels that light enters, to amplifying units provided in the pixels, and output signals, which are amplified by the amplifying units, from the pixels. In the amplified type solid-state imaging devices, a plurality of such pixels are arranged in a two-dimensional matrix. In the amplified solid-state imaging devices, for example, there is a CMOS type solid-state imaging device using CMOS (Complementary Metal Oxide Semiconductor) transistors.

For example, Japanese Unexamined Patent Application, First Publication No. 2010-160314 suggests a CMOS type solid-state imaging device that includes a plurality of pairs of photoelectric conversion units (photodiodes) that not only obtain imaging signals but also receive a light beam that enters an imaging optical system from a subject, passing through a pair of partial regions (for example, left and right pupil portions) in an exit pupil of an imaging optical system, and generate pixel signals corresponding to the respective partial regions, and that utilizes imaging elements capable of focus detection of a phase difference detection method.

SUMMARY OF THE INVENTION

A solid-state imaging device related to a first aspect of the invention is a solid-state imaging device including a first substrate having a plurality of first photoelectric conversion units; a second substrate having a plurality of second photoelectric conversion units and a first connection electrically connected to the first substrate; and a third substrate having a circuit that processes a signal and a second connection electrically connected to the second substrate. At least one of the first substrate and the second substrate has a selector that selects the angle of a light ray that is transmitted through the first substrate and enters the second substrate.

According to a second aspect of the invention, in the above first aspect, the selector may be formed from a material that shields light, and the selector may be a layer that has an opening portion that transmits only a portion of the light that has entered the first substrate and has been transmitted through the first photoelectric conversion units.

According to a third aspect of the invention, in the above second aspect, the layer may constitute a wiring line within the first substrate.

A solid-state imaging device of a fourth aspect of the invention is a solid-state imaging device including a first substrate having a plurality of first photoelectric conversion units; and a second substrate having a connection electrically connected to the first substrate, a plurality of second photoelectric conversion units, and a circuit that processes a signal. At least one of the first substrate and the second substrate has a selector that selects the angle of the light ray that is transmitted through the first substrate and enters the second substrate.

According to a fifth aspect of the invention, in the above fourth aspect, the selector may be formed from a material that shields light, and the selector may be a layer that has an opening portion that transmits only a portion of the light that has entered the first substrate and has been transmitted through the first photoelectric conversion units.

According to a sixth aspect of the invention, in the above fifth aspect, the layer constitutes a wiring line within the first substrate or the second substrate.

According to a seventh aspect of the invention, in the above first aspect, the number of the plurality of first photoelectric conversion units and the number of the plurality of second photoelectric conversion units may be the same, and a light transmitted through only one first photoelectric conversion unit among the plurality of first photoelectric conversion units may enter one second photoelectric conversion unit among the plurality of second photoelectric conversion units.

According to an eighth aspect of the invention, in the above fourth aspect, the number of the plurality of first photoelectric conversion units and the number of the plurality of second photoelectric conversion units may be the same, and the light transmitted through only one first photoelectric conversion unit among the plurality of first photoelectric conversion units may enter one second photoelectric conversion unit among the plurality of second photoelectric conversion units.

According to a ninth aspect of the invention, in the above first aspect, the number of the plurality of second photoelectric conversion units may be smaller than the number of the plurality of first photoelectric conversion units, and the light transmitted through the plurality of first photoelectric conversion units may enter one second photoelectric conversion unit among the plurality of second photoelectric conversion units.

According to a tenth aspect of the invention, in the above fourth aspect, the number of the plurality of second photoelectric conversion units may be smaller than the number of the plurality of first photoelectric conversion units, and the light transmitted through the plurality of first photoelectric conversion units may enter one second photoelectric conversion unit among the plurality of second photoelectric conversion units.

A camera system related to an eleventh aspect of the invention may include the above solid-state imaging device.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will be described below referring to the drawings.

First Embodiment

First, a first embodiment of the invention will be described.FIG. 1shows the configuration of a camera system according to the present embodiment. The camera system of the present embodiment may be, besides digital cameras, digital camcorders, endoscopes, camera modules for cellular phones, or the like, if the electronic equipment has an imaging function. The camera system shown inFIG. 1has an imaging lens101, a solid-state imaging device200, an image processing unit103, a control unit104, a liquid crystal monitor105, a storage medium106, and an operation input unit107.

The imaging lens101forms a subject image to be formed by the light from a subject, on a two-dimensional pixel array arranged in the solid-state imaging device200. The solid-state imaging device200outputs signals (imaging signals for image formation and signals for focus detection) based on the subject image formed on the two-dimensional pixel array in which a number of pixels are arrayed. The image processing unit103has the function of performing signal processing, such as chrominance signal processing, gain processing, and white balance processing, on the imaging signals output from the solid-state imaging device200, and converts the processed signals into signals in a format that can be displayed on the liquid crystal monitor105or stored in the storage medium106. Additionally, the image processing unit103performs focus detection using a phase difference detection method, on the basis of the signals for focus detection output from the solid-state imaging device200.

The control unit104is electrically connected to the respective units within the camera system, and controls the camera system. The operation of the control unit104is specified in a program stored in a built-in ROM of the camera system. The control unit104reads this program and performs various kinds of control, such as auto-focusing, according to the contents specified by the program. The liquid crystal monitor105displays an image on the basis of the imaging signals processed by the image processing unit103. The storage medium106stores image data based on the imaging signals processed by the image processing unit103. The operation input unit107has buttons, switches, or the like to be operated by a user. An operation result of a user is input to the control unit104as a signal via the operation input unit107. For example, setting of a shooting mode, shutter release of a still image, and instructions for the start and end of moving image shooting are performed via the operation input unit107.

In the camera system of the present embodiment, the imaging signals for image formation and the signals for focus detection can be obtained by the solid-state imaging device200, and it is not necessary to provide separate sensors in order to obtain the signals for focus detection. Therefore, the configuration of the equipment can be simplified.

FIG. 2shows the configuration of the solid-state imaging device200in cross-sectional view. The solid-state imaging device200is configured to have a first substrate210in which a plurality of photoelectric conversion units215(first photoelectric conversion units) are formed, a second substrate220in which a plurality of photoelectric conversion units225(second photoelectric conversion units) are formed, and a third substrate230in which a plurality of MOS transistors are formed. The first substrate210, the second substrate220, and the third substrate230have a laminated structure, and are overlapped and bonded together so that mutual principal surfaces face each other.

Light enters from the upper side in the drawing, and micro lenses240that focus the light from a subject and color filters250corresponding to predetermined colors are formed on the surface of the first substrate210.

As shown inFIG. 2, the first substrate210is constituted by a semiconductor substrate211in which the photoelectric conversion units215are formed, and a multilayer wiring layer in which an insulating film212, wiring lines213(selectors), and vias214are formed. The photoelectric conversion units215are, for example, embedded photodiodes constituted by an N-type well that is formed in a P-type well layer and a P+-type impurity region that have contact with the N-type well and is formed on the surface side of the P-type well layer.

The wiring lines213are laminated via the insulating film212, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias214. InFIG. 2, the wiring lines213have four wiring layers. One wiring layer213aamong the wiring lines213has opening portions216for allowing only a portion of the light that has entered the first substrate210and has been transmitted through the photoelectric conversion units215to be selectively transmitted therethrough, and the remaining wiring layers are arranged so as not to shield the light that enters the opening portions216. The wiring line213ais used for transmission of signals within the first substrate210or supply of a power-source voltage or a ground voltage, and is also used as a shielding layer for light. For this reason, the wiring line213ais made of materials (for example, metals, such as aluminum and copper) that have conductivity and have light shielding characteristics. In the present embodiment, the wiring layer213ais arranged on the second substrate220side of the first substrate210.

FIG. 3shows a state where only a portion equivalent to three pixels of the solid-state imaging device200shown inFIG. 2is seen in plan view.

The planar positional relationship of the wiring line213, the opening portions216, the photoelectric conversion units215, and the micro lenses240is as shown inFIG. 3. The photoelectric conversion units215are formed in a square shape, and the micro lenses240are formed in a circular shape so as to cover the photoelectric conversion units215. The opening portions216are formed in a slit shape that is vertically elongated.

As shown inFIG. 2, the second substrate220is constituted by a semiconductor substrate221in which the photoelectric conversion units225and through vias226(first connection) are formed, and a multilayer wiring layer in which an insulating film222, wiring lines223and vias224and227are formed. The photoelectric conversion units225are, for example, photodiodes similarly to the photoelectric conversion units215. Additionally, the photoelectric conversion units225are arranged to face the photoelectric conversion units215and the opening portions216so that the light that has entered the solid-state imaging device200enters the photoelectric conversion units225. The through vias226are electrically connected to the vias214of the first substrate210at an interface between the first substrate210and the second substrate220, and are electrically connected to the vias224of the second substrate220at an interface between the semiconductor substrate221and the insulating film222. The through vias226are insulated from the semiconductor substrate221. The vias227are connected to the semiconductor substrate221.

The wiring lines223are laminated via the insulating film222, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias224and227. InFIG. 2, the wiring lines223have three wiring layers. Since the wiring lines223are used for transmission of signals within the second substrate220or supply of a power-source voltage or a ground voltage, the wiring lines are made of materials (for example, metals, such as aluminum and copper) that have conductivity.

As shown inFIG. 2, the third substrate230is constituted by a semiconductor substrate231that has a plurality of MOS transistors including an impurity region235and a gate236, and a multilayer wiring layer in which an insulating film232, wiring lines233, and vias234and237(second connection) are formed. The wiring lines233are laminated via the insulating film232, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias234and237. InFIG. 2, the wiring lines233have three wiring layers.

Since the wiring lines233are used for transmission of signals within the third substrate230or supply of a power-source voltage or a ground voltage, the wiring lines are made of materials (for example, metals, such as aluminum and copper) that have conductivity. The vias234and the vias224are electrically connected at an interface between the second substrate220and the third substrate230. Additionally, the vias237and the vias227are electrically connected at the interface between the second substrate220and the third substrate230.

The light that has entered the solid-state imaging device200is condensed by the micro lenses240and enters the photoelectric conversion units215. This light is photoelectrically converted by the photoelectric conversion units215, and signals according to the quantity of light are generated. The signals generated by the photoelectric conversion units215are transmitted to the third substrate230via the vias214and multilayer wiring layer (213) of the first substrate210, and the through vias226, vias224, and multilayer wiring layer (223) of the second substrate220. The signals transmitted to the third substrate230are transmitted via the vias234and multilayer wiring layer (233) of the third substrate230, are processed by circuits, such as the MOS transistors of the third substrate230, and are output as imaging signals.

Additionally, the light transmitted through the semiconductor substrate211of the first substrate210in the light that has entered the solid-state imaging device200passes through the opening portions216, and enters the photoelectric conversion units225of the second substrate220. This light is photoelectrically converted by the photoelectric conversion units225, and signals according to the quantity of light are generated. Selecting entering light two-dimensionally by means of the opening portions216is equal to selecting the light ray angle of the light that enters the solid-state imaging device200. Hence, the signals obtained by the photoelectric conversion units225correspond to the light ray angle of the light that has entered the solid-state imaging device200. The signals generated by the photoelectric conversion units225are transmitted to the third substrate230via the vias227and multilayer wiring layer (223) of the second substrate220. The signals transmitted to the third substrate230are transmitted via the vias237and multilayer wiring layer of the third substrate230, and are processed by circuits, such as the MOS transistors of the third substrate230, and are output as signals for focus detection.

FIG. 4shows the configuration of only a portion equivalent to two pixels including the photoelectric conversion units225that become a pair for focus detection of the phase difference detection method in the solid-state imaging device200shown inFIG. 2, in cross-sectional view.FIG. 5shows a state where only a portion equivalent to two pixels including the photoelectric conversion units225that become the pair for focus detection of the phase difference detection method in the solid-state imaging device200shown inFIG. 2, is seen in plan view. An opening portion216-L is formed in the wiring line213aof a left pixel, and an opening portion216-R is formed in the wiring line213aof a right pixel. The opening portion216-R and the opening portion216-L are arranged so that the planar positions thereof within the respective pixels become bilaterally symmetrical. A plurality of pixels that become pairs arranged at positions where the opening portions216are bilaterally symmetrical or vertically symmetrical as in the opening portion216-R and the opening portion216-L are arranged within an imaging surface of the solid-state imaging device200. The signals generated by the photoelectric conversion units225of these pixels that become pairs can be used for focus detection.

In the above solid-state imaging device200, when the solid-state imaging device200is seen in plan view, the photoelectric conversion units225of the same number as the photoelectric conversion units215of the first substrate210are arranged in the second substrate220so as to be located at the same positions as the photoelectric conversion units215of the first substrate210, and both are correlated on a one-to-one basis. In a case where one photoelectric conversion unit215is arranged in each of the effective pixels of the imaging surface, it is possible to arrange the photoelectric conversion units225of the same number as the effective pixels of the imaging surface. For this reason, the focus detection can be performed even in a case where the light from a subject is focused on any location of the effective pixel region of the imaging surface.

Next, a modification example of the present embodiment will be described.FIG. 6shows the configuration of a solid-state imaging device201related to the present modification example in cross-sectional view. The configuration of the solid-state imaging device201shown inFIG. 6is a configuration in which the first substrate210of the above solid-state imaging device200is substituted with a first substrate260and the second substrate220is substituted with a second substrate270.

As shown inFIG. 6, the first substrate260is constituted by a semiconductor substrate261in which photoelectric conversion units265are formed, and a multilayer wiring layer in which an insulating film262, wiring lines263, and vias264are formed. One wiring layer263aamong the wiring lines263has opening portions266for allowing only a portion of the light that has entered the first substrate260and has been transmitted through the photoelectric conversion units265to be selectively transmitted therethrough, and the remaining wiring layers are arranged so as not to shield the light that enters the opening portions266. One opening portion266is formed in each pixel.

In the present embodiment, the wiring layer263ais arranged on the second substrate270side of the first substrate260.

As shown inFIG. 6, the second substrate270is constituted by a semiconductor substrate271in which photoelectric conversion units275and through vias276are formed, and a multilayer wiring layer formed by an insulating film272, wiring lines273, and vias274and277. In the above solid-state imaging device200, the photoelectric conversion units265are formed on a one-to-one basis with respect to the photoelectric conversion units215, whereas in the solid-state imaging device201of the present modification example, one photoelectric conversion unit275is formed with respect to two photoelectric conversion units265.

In other words, in the above solid-state imaging device200, the number of the photoelectric conversion units215and the number of the photoelectric conversion units225are the same, and the light transmitted through only one photoelectric conversion unit215enters one photoelectric conversion unit225.

In contrast, in the solid-state imaging device201of the present modification example, the number of the photoelectric conversion units265is twice the number of the photoelectric conversion units275, and the light transmitted through two photoelectric conversion units265enters one photoelectric conversion units275.

For this reason, the region of the photoelectric conversion units275in the solid-state imaging device201of the present modification example is larger than the region of the photoelectric conversion units225in the above solid-state imaging device200. By enlarging the region of the photoelectric conversion units in this way, the S/N ratio of signals to be obtained can be improved. Although a configuration in which the number of the photoelectric conversion units265and the number of the photoelectric conversion units275become 2:1 is adopted in the present embodiment, the light from substantially the same portion of a subject may be transmitted through a plurality of photoelectric conversion units265and enter the same photoelectric conversion unit275, and the ratio of the number of the photoelectric conversion units265and the number of the photoelectric conversion units275may be changed to ratios other than the above ratio.

In the present embodiment, the first substrate210or260is formed with the wiring lines213or263in which the opening portions216or266for selecting the light ray angle of the light that enters the photoelectric conversion units225or275of the second substrate220or270are formed. Instead of this, however, a layer that has the same function may be formed in the second substrate220or270.

As described above, according to the present embodiment, the photoelectric conversion units are arranged in both the first substrate210or260and the second substrate220or270. Thus, as compared to a case where photoelectric conversion units for obtaining imaging signals and photoelectric conversion units for obtaining signals for focus detection are arranged in the same plane, signals to be used for the focus detection of the phase difference detection method can be generated while reducing a decline in the resolution of the imaging signals. Additionally, by using the wiring lines213or263as a layer that selects the light ray angle, the opening portions216or266can be easily formed by a semiconductor process. Moreover, the light ray angle can be easily selected by forming the opening portions216or266in the wiring lines213or263.

Additionally, by arranging the photoelectric conversion units225of the same number as the photoelectric conversion units215of the first substrate210in the second substrate220and correlating both on a one-to-one basis, the focus detection can be performed even in a case where the light from a subject is focused on any location of the effective pixel region of the imaging surface. Additionally, by making the number of the photoelectric conversion units265of the first substrate260more than the number of the photoelectric conversion units275of the second substrate270, the S/N ratio of signals to be used for the focus detection of the phase difference detection method can be improved.

Second Embodiment

Next, a second embodiment of the invention will be described. The configuration of a camera system according to the present embodiment is a configuration in which the solid-state imaging device200inFIG. 1is substituted with a solid-state imaging device300shown inFIG. 7.

FIG. 7shows the configuration of the solid-state imaging device300in cross-sectional view. The solid-state imaging device300is configured to have a first substrate310in which a plurality of photoelectric conversion units315(first photoelectric conversion units) are formed, and a second substrate320in which a plurality of photoelectric conversion units325(second photoelectric conversion units) and a plurality of MOS transistors are formed. The first substrate310and the second substrate320have a laminated structure, and are overlapped and bonded together so that mutual principal surfaces face each other. Light enters from the upper side in the drawing, and micro lenses330that focus the light from a subject and color filters340corresponding to predetermined colors are formed on the surface of the first substrate310.

As shown inFIG. 7, the first substrate310is constituted by a semiconductor substrate311in which the photoelectric conversion units315are formed, and a multilayer wiring layer in which an insulating film312, wiring lines313(selectors), and vias314are formed. The photoelectric conversion units315are, for example, embedded photodiodes constituted by an N-type well that is formed in a P-type well layer and a P+-type impurity region that have contact with the N-type well and is formed on the surface side of the P-type well layer.

The wiring lines313are laminated via the insulating film312, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias314. InFIG. 7, the wiring lines313have four wiring layers. One wiring layer313aamong the wiring lines313has opening portions316for allowing only a portion of the light that has entered the first substrate310and has been transmitted through the photoelectric conversion units315to be selectively transmitted therethrough, and the remaining wiring layers are arranged so as not to shield the light that enters the opening portions316. The wiring line313ais used for transmission of signals within the first substrate310or supply of a power-source voltage or a ground voltage, and is also used as a shielding layer for light. For this reason, the wiring line313ais made of materials (for example, metals, such as aluminum and copper) that have conductivity and have light shielding characteristics.

As shown inFIG. 7, the second substrate320is constituted by the photoelectric conversion units325, a semiconductor substrate321that has a plurality of MOS transistors including an impurity region326and a gate327, and a multilayer wiring layer in which an insulating film322, wiring lines323, and vias324(connections) are formed. The photoelectric conversion units325are, for example, photodiodes similarly to the photoelectric conversion units315. Additionally, the photoelectric conversion units325are arranged at positions that face the photoelectric conversion units315so that the light that has entered the solid-state imaging device300enters the photoelectric conversion units325. The wiring lines323are laminated via the insulating film322, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias324. InFIG. 7, the wiring lines323have two wiring layers, and are arranged so as not to shield the light that has passed through the opening portions316.

In the present embodiment, the wiring layer313ais arranged on the second substrate320side of the first substrate310.

Since the wiring lines323are used for transmission of signals within the second substrate320or supply of a power-source voltage or a ground voltage, the wiring lines are made of materials (for example, metals, such as aluminum and copper) that have conductivity. The vias324and the vias314are electrically connected at an interface between the first substrate310and the second substrate320.

The light that has entered the solid-state imaging device300is condensed by the micro lenses330and enters the photoelectric conversion units315. This light is photoelectrically converted by the photoelectric conversion units315, and signals according to the quantity of light are generated. The signals generated by the photoelectric conversion units315are transmitted to the second substrate320via the vias314and multilayer wiring layer (313) of the first substrate310. The signals transmitted to the second substrate320are transmitted via the vias324and multilayer wiring layer (323) of the second substrate320, are processed by circuits, such as the MOS transistors of the second substrate320, and are output as imaging signals.

Additionally, the light transmitted through the semiconductor substrate311of the first substrate310in the light that has entered the solid-state imaging device300passes through the opening portions316, and enters the photoelectric conversion units325of the second substrate320. This light is photoelectrically converted by the photoelectric conversion units325, and signals according to the quantity of light are generated. Selecting entering light two-dimensionally by means of the opening portions316is equal to selecting the light ray angle of the light that enters the solid-state imaging device300. Hence, the signals obtained by the photoelectric conversion units325correspond to the light ray angle of the light that has entered the solid-state imaging device300. The signals generated by the photoelectric conversion units325are transmitted via the multilayer wiring layer of the second substrate320, are processed by circuits, such as the MOS transistors of the second substrate320, and are output as signals for the focus detection.

In the present embodiment, the first substrate310is formed with the wiring lines313in which the opening portions316for selecting the light ray angle of the light that enters the photoelectric conversion units325of the second substrate320are formed. Instead of this, however, a layer that has the same function may be formed in the second substrate320.

As described above, according to the present embodiment, the photoelectric conversion units are arranged in both the first substrate310and the second substrate320. Thus, as compared to a case where photoelectric conversion units for obtaining imaging signals and photoelectric conversion units for obtaining signals for focus detection are arranged in the same plane, signals to be used for the focus detection of the phase difference detection method can be generated while reducing a decline in the resolution of the imaging signals. Additionally, by using the wiring lines313as a layer that selects the light ray angle, the opening portions316can be easily formed by a semiconductor process. Moreover, the light ray angle can be easily selected by forming the opening portions316in the wiring lines313.

Additionally, by arranging the photoelectric conversion units325of the same number as the photoelectric conversion units315of the first substrate310in the second substrate320and correlating both on a one-to-one basis, the focus detection can be performed even in a case where the light from a subject is focused on any location of the effective pixel region of the imaging surface.

Third Embodiment

Next, a third embodiment of the invention will be described. The configuration of a camera system according to the present embodiment is a configuration in which the solid-state imaging device200inFIG. 1is substituted with a solid-state imaging device400shown inFIG. 8.

FIG. 8shows the configuration of the solid-state imaging device400in cross-sectional view. The solid-state imaging device400is configured to have a first substrate410in which a plurality of photoelectric conversion units415(first photoelectric conversion units) are formed, and a second substrate420in which a plurality of photoelectric conversion units425(second photoelectric conversion units) and a plurality of MOS transistors are formed. The first substrate410and the second substrate420have a laminated structure, and are overlapped and bonded together so that mutual principal surfaces face each other. Light enters from the upper side in the drawing, and micro lenses430that focus the light from a subject and color filters440corresponding to predetermined colors are formed on the surface of the first substrate410.

As shown inFIG. 8, the first substrate410is constituted by a semiconductor substrate411in which the photoelectric conversion units415are formed, and a multilayer wiring layer in which an insulating film412, wiring lines413, and vias414are formed. The photoelectric conversion units415are, for example, embedded photodiodes constituted by an N-type well that is formed in a P-type well layer and a P+-type impurity region that have contact with the N-type well and is formed on the surface side of the P-type well layer.

The wiring lines413are laminated via the insulating film412, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias414. InFIG. 8, the wiring lines413have four wiring layers. The wiring lines413are arranged so as not to shield the light that enters the first substrate410, is transmitted through the photoelectric conversion units415, and enters opening portions428. The wiring lines413are used for transmission of signals within the first substrate410or supply of a power-source voltage or a ground voltage, and are also used as a shielding layer for light. For this reason, the wiring lines413are made of materials (for example, metals, such as aluminum and copper) that have conductivity and have light shielding characteristics.

As shown inFIG. 8, the second substrate420is constituted by the photoelectric conversion units425, a semiconductor substrate421that has a plurality of MOS transistors including an impurity region426and a gate427, and a multilayer wiring layer in which an insulating film422, wiring lines423(selectors), and vias424(connections) are formed. The insulating film422is arranged on the first substrate410side. The photoelectric conversion units425are, for example, photodiodes similarly to the photoelectric conversion units415. Additionally, the photoelectric conversion units425are arranged at positions that face the photoelectric conversion units415so that the light that has entered the solid-state imaging device400enters the photoelectric conversion units425. The wiring lines423are laminated via the insulating film422, and form the multilayer wiring layer by connecting respective wiring layers by means of the vias424. InFIG. 8, the wiring lines423have two wiring layers.

One wiring layer423aamong the wiring lines423has opening portions428for allowing only a portion of the light that has entered the first substrate410and has been transmitted through the photoelectric conversion units415to be selectively transmitted therethrough, and the remaining wiring layers are arranged so as not to shield the light that enters the opening portions428. Since the wiring lines423are used for transmission of signals within the second substrate420or supply of a power-source voltage or a ground voltage and are also used as a shielding layer for light, the wiring lines are made of materials (for example, metals, such as aluminum and copper) that have conductivity and light shielding characteristics. The vias424and the vias414are electrically connected at an interface between the first substrate410and the second substrate420.

The light that has entered the solid-state imaging device400is condensed by the micro lenses430and enters the photoelectric conversion units415. This light is photoelectrically converted by the photoelectric conversion units415, and signals according to the quantity of light are generated. The signals generated by the photoelectric conversion units415are transmitted to the second substrate420via the vias414and multilayer wiring layer of the first substrate410. The signals transmitted to the second substrate420are transmitted via the vias424and multilayer wiring layer of the second substrate420, are processed by circuits, such as the MOS transistors of the second substrate420, and are output as imaging signals.

Additionally, the light transmitted through the semiconductor substrate411of the first substrate410in the light that has entered the solid-state imaging device400enters the second substrate420. The light that has entered the second substrate420passes through the opening portions428, and enters the photoelectric conversion units425. This light is photoelectrically converted by the photoelectric conversion units425, and signals according to the quantity of light are generated. Selecting entering light two-dimensionally by means of the opening portions428is equal to selecting the light ray angle of the light that enters the solid-state imaging device400. Hence, the signals obtained by the photoelectric conversion units425correspond to the light ray angle of the light that has entered the solid-state imaging device400. The signals generated by the photoelectric conversion units425are transmitted via the multilayer wiring layer of the second substrate420, are processed by circuits, such as the MOS transistors of the second substrate420, and are output as signals for the focus detection.

In the solid-state imaging device300of the second embodiment, the photoelectric conversion units315are formed on a one-to-one basis with respect to the photoelectric conversion units325, whereas in the solid-state imaging device400of the present embodiment, one photoelectric conversion unit425is formed with respect to two photoelectric conversion units415. In other words, in the solid-state imaging device300of the second embodiment, the number of the photoelectric conversion units315and the number of the photoelectric conversion units325are the same, and the light transmitted through only one photoelectric conversion unit315enters one photoelectric conversion unit325. In contrast, in the solid-state imaging device400of the present embodiment, the number of the photoelectric conversion units415is twice the number of the photoelectric conversion units425, and the light transmitted through two photoelectric conversion units415enters one photoelectric conversion units425.

For this reason, the region of the photoelectric conversion units425in the solid-state imaging device400of the present embodiment is larger than the region of the photoelectric conversion units325in the solid-state imaging device300of the second embodiment. By enlarging the region of the photoelectric conversion units425in this way, the S/N ratio of signals to be obtained can be improved. Although a configuration in which the number of the photoelectric conversion units415and the number of the photoelectric conversion units425become 2:1 is adopted in the present embodiment, the light from substantially the same portion of a subject may be transmitted through a plurality of photoelectric conversion units415and enter the same photoelectric conversion unit425, and the ratio of the number of the photoelectric conversion units415and the number of the photoelectric conversion units425may be changed to ratios other than the above ratio.

In the present embodiment, the second substrate420is formed with the wiring lines423in which the opening portions428for selecting the light ray angle of the light that enters the photoelectric conversion units425of the second substrate420are formed. Instead of this, however, a layer that has the same function may be formed in the first substrate410.

As described above, according to the present embodiment, the photoelectric conversion units are arranged in both the first substrate410and the second substrate420. Thus, as compared to a case where photoelectric conversion units for obtaining imaging signals and photoelectric conversion units for obtaining signals for focus detection are arranged in the same plane, signals to be used for the focus detection of the phase difference detection method can be generated while reducing a decline in the resolution of the imaging signals. Additionally, by using the wiring lines423as a layer that selects the light ray angle, the opening portions428can be easily formed by a semiconductor process. Moreover, the light ray angle can be easily selected by forming the opening portions428in the wiring lines423.

Additionally, by making the number of the photoelectric conversion units415of the first substrate410more than the number of the photoelectric conversion units425of the second substrate420, the S/N ratio of signals to be used for the focus detection of the phase difference detection method can be improved.

For example, in the above-embodiments, while the first substrate has the wiring layer (selector), at least one of the first substrate and the second substrate may have the wiring layer.