Patent Description:
There are technologies to extend the dynamic range of image pick-up apparatuses in various methods. For example, a time-division method in which images are taken with different sensitivities at different times so that the images taken at the different times are synthesized is known.

Additionally, for example, a space-division method in which light receiving elements with different sensitivities are provided in an image pick-up apparatus so that synthesizing a plurality of images taken with the light receiving elements, respectively, extends the dynamic range of the image pick-up apparatus is known (for example, see Patent Literature <NUM> and <NUM>).

Furthermore, for example, an in-pixel memory method in which a memory in which the charge overflowing from a photodiode is accumulated is provided on each pixel in an image pick-up apparatus so that the amount of charge accumulated in an exposure period is increased and the increase extends the dynamic range of the image pick-up apparatus (for example, see Patent Literature <NUM>).

Patent Literature <NUM> relates to a 3D color image sensor including a substrate having a plurality of first photodiodes and a plurality of second photodiodes. A light filter array is disposed on the first and second photodiodes. The sensitive area of the first photodiodes is larger than the sensitive area of the second photodiodes. First and second photodiodes are isolated by an insulator which may be formed as shallow trench isolations. Further examples of solid-state imaging devices are disclosed in Patent Literature <NUM> to <NUM>.

PTL <NUM> discloses an imaging device provided with a plurality of pixel units, each pixel unit comprising a low sensitivity pixel and a high sensitivity pixel. Polarization grids are provided on the low sensitivity pixels. The low sensitivity pixels are off-set within a pixel group comprising two pixel units. The polarization grids are arranged in a same direction.

Increasing the number of divided times in the time division method or increasing the number of divided spaces in the space division method can extend the dynamic range of an image pick-up apparatus. On the other hand, however, the increase in number of divided times or divided spaces degrades the quality of images, for example, due to the occurrence of an artifact or the decrease in resolution.

Additionally, the limit of the memory capacity limits the extension of the dynamic range in the in-pixel memory method.

In light of the foregoing, it is desirable to extend the dynamic range of an image pick-up apparatus without degrading the quality of images.

According to a first aspect the invention provides an imaging device in accordance with claim <NUM>. According to a second aspect the invention provides an electronic apparatus in accordance with claim <NUM>. Further aspects of the invention are set forth in the dependent claims, the drawings and the following description of embodiments. An image pick-up apparatus according to the invention is defined in claim <NUM>.

A lens used to collect light entering the second opto-electronic converter may not be formed on the second opto-electronic converter.

The image pick-up apparatus may be a backside-illumination image sensor.

The image pick-up apparatus may be a front-side-illumination image sensor.

The light-blocking film may be formed on a lower or upper side of a wiring layer formed on the second opto-electronic converter.

The light-blocking film may be an amorphous silicon film, a polysilicon film, a Ge film, a GaN film, a CdTe film, a GaAs film, an InP film, a CuInSe2 film, Cu2S, a CIGS film, a non-conductive carbon film, a black resist film, an organic opto-electronic conversion film, or a metal film.

According to an aspect of the present invention, the dynamic range of an image pick-up apparatus can be extended without the degradation of the quality of images.

The modes for carrying out the present technology (hereinafter, referred to as embodiments) will be described hereinafter.

Note that the expression "the present technology", unless stated differently, does relate to not claimed examples that are useful for understanding the invention.

An embodiment of the invention is depicted in <FIG>.

Note that the embodiments which are not claimed but are useful for understanding the invention as well as the embodiments according to the invention will be described in the following order.

<FIG> is a schematic system configuration diagram of a CMOS image sensor that is an image pick-up apparatus using the present technology, for example, a pick-up apparatus using an X-Y address system. In this example, the CMOS image sensor is an image sensor applying or partially using a CMOS process.

A CMOS image sensor <NUM> according to the present exemplary application includes a pixel array unit <NUM> formed on a semiconductor substrate (chip) (not illustrated), and a peripheral circuit unit integrated with the pixel array unit <NUM> on the same semiconductor substrate. The peripheral circuit unit includes, for example, a vertical drive unit <NUM>, a column processing unit <NUM>, a horizontal drive unit <NUM>, and a system control unit <NUM>.

The CMOS image sensor <NUM> further includes a signal processing unit <NUM>, and a data storage unit <NUM>. The signal processing unit <NUM> and the data storage unit <NUM> can be mounted on the same substrate on which the CMOS image sensor <NUM> is mounted, or can be placed on a different substrate from the substrate on which the CMOS image sensor <NUM> is mounted. Additionally, the process that each of the signal processing unit <NUM> and the data storage unit <NUM> performs can be processed by an external signal processing unit provided on a different substrate from the substrate on which the CMOS image sensor <NUM> is mounted, such as a Digital Signal Processor (DSP) circuit or by software.

In the pixel array unit <NUM>, unit pixels (hereinafter, sometimes referred to merely as "pixels") are arranged in a row direction and a column direction, in other words, two-dimensionally arranged in rows and columns. The unit pixel includes an opto-electronic converter that generates and accumulates the charge corresponding to the amount of light that the opto-electronic converter receives. In this example, the row direction is a direction in which pixels are arranged in a pixel row (namely, a horizontal direction), and the column direction is a direction in which pixels are arranged in a pixel column (namely, a vertical direction). The concrete configuration of the circuit of the unit pixel and the detailed configuration of the unit pixel will be described below.

In the pixel array unit <NUM>, pixel drive lines <NUM> are distributed to the pixel rows in the row direction, respectively, and vertical signal lines <NUM> are distributed to pixel columns in the column direction, respectively, in the pixel arrangement in rows and columns. The pixel drive line <NUM> transmits a drive signal used for the drive to read a signal from a pixel. <FIG> illustrates the pixel drive line <NUM> as a wire. However, the number of wires is not limited to one. First ends of the pixel drive lines <NUM> are connected to output terminals of the vertical drive unit <NUM> that corresponds to the rows, respectively.

The vertical drive unit <NUM> includes a shift register or an address decoder, and drives the pixels in the pixel array unit <NUM>, for example, simultaneously or row by row. In other words, the vertical drive unit <NUM> cooperates with a system control unit <NUM> that controls the vertical drive unit <NUM> so as to work as a drive unit that controls the operation of each pixel in the pixel array unit <NUM>. The illustration of the concrete configuration of the vertical drive unit <NUM> is omitted. However, the vertical drive unit <NUM> generally includes two scanning systems; a readout scanning system, and a discharge scanning system.

The readout scanning system sequentially selects and scans the unit pixels in the pixel array unit <NUM> row by row so as to read signals from the unit pixels. The signal read from a unit pixel is an analog signal. The discharge scanning system scans a row in discharge scanning the exposure period earlier than the time when the readout scanning system reads and scans the row in readout scanning.

The discharge scanning by the discharge scanning system discharges unnecessary charge from the opto-electronic converters of the unit pixels in the read row. This discharge resets the opto-electronic converters. Then, the discharge of the unnecessary charge (the resetting) by the discharge scanning system causes so-called electronic shutter operation. In this example, the electronic shutter operation is the operation in which the charge in the opto-electronic converter is discharged and exposure is newly started (the accumulation of charge is started).

The signal read in a readout operation by the readout scanning system corresponds to the amount of light received in and after the readout operation or electronic shutter operation immediately before the readout operation. Then, the period between the readout timing by the readout operation immediately before the current readout operation or the discharge timing by the electronic shutter operation immediately before the current readout operation and the readout timing by the current readout operation is the period of exposure of charge in the unit pixel.

A signal is output from each unit pixel in the pixel row selected and scanned by the vertical drive unit <NUM>. The signal is input via each vertical signal line <NUM> pixel column by pixel column to the column processing unit <NUM>. The column processing unit <NUM> processes the signals output via the vertical signal line <NUM> from the pixels in the selected row in the pixel array unit <NUM> pixel column by pixel column in a predetermined signal process, and temporarily stores the pixel signals after the signal process.

Specifically, the column processing unit <NUM> performs at least a noise removal process, for example, a Correlated Double Sampling (CDS) process, or a Double Data Sampling (DDS) process as the signal process. For example, the CDS process removes reset noise or fixed pattern noise specific to a pixel such as the variations in the threshold of the amplification transistor in the pixel. In addition to the noise removal process, the column processing unit <NUM> can have, for example, an analog-digital (AD) conversion function so that the column processing unit <NUM> can convert an analog pixel signal into a digital signal and output the digital signal.

The horizontal drive unit <NUM> includes, for example, a shift register and an address decoder so as to sequentially select a unit circuit corresponding to the pixel column of the column processing unit <NUM>. This selection and scanning by the horizontal drive unit <NUM> sequentially outputs the pixel signals processed unit circuit by unit circuit in the signal process by the column processing unit <NUM>.

The system control unit <NUM> includes, for example, a timing generator that generates various timing signals so as to control the drive, for example, of the vertical drive unit <NUM>, the column processing unit <NUM>, and the horizontal drive unit <NUM> on the basis of various times generated by the timing generator.

The signal processing unit <NUM> includes at least an arithmetic process function so as to process the pixel signal output from the column processing unit <NUM> in various signal processes including the arithmetic process. The data storage unit <NUM> temporarily stores the data necessary for a signal process so that the signal processing unit <NUM> performs the signal process.

<FIG> is a circuit diagram illustrating the configuration of the unit pixel <NUM> placed in the pixel array unit <NUM> in <FIG>.

The unit pixel <NUM> includes a first opto-electronic converter <NUM>, a first transfer gate unit <NUM>, a second opto-electronic converter <NUM>, a second transfer gate unit <NUM>, a third transfer gate unit <NUM>, a charge accumulation unit <NUM>, a reset gate unit <NUM>, a floating diffusion (FD) unit <NUM>, an amplification transistor <NUM>, and a selection transistor <NUM>.

Additionally, the unit pixel <NUM> is wired with a plurality of drive lines as the pixel drive lines <NUM> illustrated in <FIG>, for example pixel row by pixel row. Then, various drive signals TGL, TGS, FCG, RST, and SEL are supplied via the drive lines from the vertical drive unit <NUM> illustrated in <FIG>. These drive signals are a pulse signal that is in an active state at a high level (for example, the power-supply voltage VDD) and is in a non-active state at a low level (for example, negative potential) because each transistor of the unit pixel <NUM> is an NMOS transistor.

The first opto-electronic converter <NUM> includes, for example, a PN-junction photodiode. The first opto-electronic converter <NUM> generates and accumulates charge corresponding to the amount of light that the first opto-electronic converter <NUM> receives.

The first transfer gate unit <NUM> is connected between the first opto-electronic converter <NUM> and the FD unit <NUM>. The drive signal TGL is applied to the gate electrode of the first transfer gate unit <NUM>. When the drive signal TGL is turned into the active state, the first transfer gate unit <NUM> becomes conductive so that the charge accumulated in the first opto-electronic converter <NUM> is transferred to the FD unit <NUM> via the first transfer gate unit <NUM>.

The second opto-electronic converter <NUM> includes, for example, a PN-junction photodiode, similarly to the first opto-electronic converter <NUM>. The second opto-electronic converter <NUM> generates and accumulates the charge corresponding to the amount of light that the second opto-electronic converter <NUM> receives.

In comparison between the first opto-electronic converter <NUM> and the second opto-electronic converter <NUM>, the light-receiving surface of the first opto-electronic converter <NUM> has a larger area and a higher sensitivity than the area and sensitivity of the second opto-electronic converter <NUM>. As described above, the unit pixel <NUM> includes two opto-electronic converters having different sensitivities. In other words, the first opto-electronic converter <NUM> works as a high-sensitivity pixel while the second opto-electronic converter <NUM> works as a low-sensitivity pixel.

The second transfer gate unit <NUM> is connected between the charge accumulation unit <NUM> and the FD unit <NUM>. The drive signal FCG is applied to the gate electrode of the second transfer gate unit <NUM>. When the drive signal FCG is turned into the active state, the second transfer gate unit <NUM> becomes conductive so that the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound or electrically connected to one another.

The third transfer gate unit <NUM> is connected between the second opto-electronic converter <NUM> and the charge accumulation unit <NUM>. The drive signal TGS is applied to the gate electrode of the third transfer gate unit <NUM>. When the drive signal TGS is turned into the active state, the third transfer gate unit <NUM> becomes conductive so that the charge accumulated in the second opto-electronic converter <NUM> is transferred via the third transfer gate unit <NUM> to the charge accumulation unit <NUM> or a region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound or electrically connected to one another.

Additionally, the potential well is slightly deeper at the lower part of the gate electrode of the third transfer gate unit <NUM> so as to form an overflow path through which the charge exceeding the amount of charge with which the second opto-electronic converter <NUM> is saturated and overflowing from the second opto-electronic converter <NUM> is transferred to the charge accumulation unit <NUM>. Note that the overflow path formed on the lower part of the gate electrode of the third transfer gate unit <NUM> is referred to merely as the overflow path of the third transfer gate unit <NUM>.

The charge accumulation unit <NUM> includes, for example, a capacitor, and is connected between the second transfer gate unit <NUM> and the third transfer gate unit <NUM>. The counter electrode of the charge accumulation unit <NUM> is connected between the charge accumulation unit <NUM> and the power-supply source VDD that supplies a power-supply voltage VDD. The charge accumulation unit <NUM> accumulates the charge transferred from the second opto-electronic converter <NUM>.

The reset gate unit <NUM> is connected between the power-supply source VDD and the FD unit <NUM>. The drive signal RST is applied to the gate electrode of the reset gate unit <NUM>. When the drive signal RST is turned into the active state, the reset gate unit <NUM> becomes conductive so that the potential of the FD unit <NUM> is reset into the level of the power-supply voltage VDD.

The FD unit <NUM> converts the charge into a voltage signal in charge-voltage conversion and outputs the voltage signal.

The gate electrode of the amplification transistor <NUM> is connected to the FD unit <NUM> while the drain electrode of the amplification transistor <NUM> is connected to the power-supply source VDD. The gate electrode and the drain electrode work as an input unit of the readout circuit that reads the charge retained in the FD unit <NUM>, namely, a so-called source follower circuit. In other words, the source electrode of the amplification transistor <NUM> is connected via the selection transistor <NUM> to the vertical signal line <NUM>, and thus the amplification transistor <NUM> forms the source follower circuit together with the constant current source <NUM> connected to a first end of the vertical signal line <NUM>.

The selection transistor <NUM> is connected between the source electrode of the amplification transistor <NUM> and the vertical signal line <NUM>. The selection signal SEL is applied to the gate electrode of the selection transistor <NUM>. When the selection signal SEL is turned into the active state, the selection transistor <NUM> is conductive so that the unit pixel <NUM> is selected. Thus, the pixel signal is output from the amplification transistor <NUM> via the selection transistor <NUM> to the vertical signal line <NUM>.

Note that the fact that each drive signal is turned into the active state is referred to also as "each drive signal is turned on" and the fact that each drive signal is turned into the non-active state is referred to also as "each drive signal is turned off". Additionally, the fact that each gate unit or each transistor becomes conductive is referred to also as "each gate unit or each transistor is turned on" and the fact that each gate unit or each transistor becomes non-conductive is referred to also as "each gate unit or each transistor is turned off".

Next, the operation of the unit pixel <NUM> will be described with reference to the timing diagrams of <FIG> and <FIG>. First, the operation of the unit pixel <NUM> at the start of exposure will be described with reference to the timing diagram of <FIG>. This process is performed, for example, by pixel row or by a plurality of pixel rows in the pixel array unit <NUM> in predetermined scanning order. Note that <FIG> illustrates the timing diagram of the horizontal synchronization signal XHS and the drive signals SEL, RST, TGS, FCG, and TGL.

First, the horizontal synchronization signal XHS is input and the process for exposure of the unit pixel <NUM> is started at a time t1.

Next, the drive signal RST is turned on and the reset gate unit <NUM> is turned on at a time t2. This resets the potential of the FD unit <NUM> into the level of the power-supply voltage VDD.

Next, the drive signals TGL, FCG, and TGS are turned on and the first transfer gate unit <NUM>, the second transfer gate unit <NUM>, and the third transfer gate unit <NUM> are turned on at a time t3. This binds the potential well of the charge accumulation unit <NUM> with the potential well of the FD unit <NUM>. Additionally, the charge accumulated in the first opto-electronic converter <NUM> is transferred via the first transfer gate unit <NUM> to the bound region in which the potential wells are bound. The charge accumulated in the second opto-electronic converter <NUM> transferred via the third transfer gate unit <NUM> to the bound region. Then, the bound region is reset.

Next, the drive signals TGL and TGS are turned off and the first transfer gate unit <NUM> and the third transfer gate unit <NUM> are turned off at a time t4. This starts the accumulation of the charge into the first opto-electronic converter <NUM> and the second opto-electronic converter <NUM> and an exposure period starts.

Next, the drive signal RST is turned off and the reset gate unit <NUM> is turned off at a time t5.

Next, the drive signal FCG is turned off and the second transfer gate unit <NUM> is turned off at a time t6. This causes the charge accumulation unit <NUM> to start accumulation of the charge overflowing from the second opto-electronic converter <NUM> and transferred through the overflow path of the third transfer gate unit <NUM>.

Then, the horizontal synchronization signal XHS is input at a time t7.

Next, the operation of the unit pixel <NUM> for reading a pixel signal will be described with reference to the timing diagram of <FIG>. This process is performed, for example, by pixel row or by a plurality of pixel rows in the pixel array unit <NUM> in predetermined scanning order after a predetermined period of time has elapsed since the process illustrated <FIG> has been performed. Note that <FIG> illustrates the timing diagram of the horizontal synchronization signal XHS and the drive signals SEL, RST, TGS, FCG, and TGL.

First, the horizontal synchronization signal XHS is input and the period of readout of the unit pixel <NUM> starts at a time t21.

The selection signal SEL is turned on and the selection transistor <NUM> is turned on at a time t22. Thus, the unit pixel <NUM> is selected.

Next, the drive signal RST is turned on and the reset gate unit <NUM> is turned on at a time t23. Thus, the potential of the FD unit <NUM> is reset into the level of the power-supply voltage VDD.

Next, the drive signal RST is turned off and the reset gate unit <NUM> is turned off at a time t24.

Next, the drive signals FCG and TGS are turned on and the second transfer gate unit <NUM> and the third transfer gate unit <NUM> are turned on at a time t25. This binds the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> and transfers the charge accumulated in the second opto-electronic converter <NUM> to the bound region in which the potential wells are bound. Thus, the charge accumulated in the second opto-electronic converter <NUM> and the charge accumulation unit <NUM> during the exposure period are accumulated in the bound region.

At the time t25, the readout of the pixel signal is started and the exposure period is completed.

Next, the drive signal TGS is turned off and the third transfer gate unit <NUM> is turned off at a time t26. This stops the transfer of the charge from the second opto-electronic converter <NUM>.

Next, the signal SL based on the potential in the region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound is output via the amplification transistor <NUM> and the selection transistor <NUM> to the vertical signal line <NUM> at a time ta between the time t26 and the time t27. The signal SL is a signal based on the charge generated in the second opto-electronic converter <NUM> and accumulated in the second opto-electronic converter <NUM> and the charge accumulation unit <NUM> during the exposure period.

Additionally, the signal SL is a signal based on the potential in the bound region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound when the charge accumulated in the second opto-electronic converter <NUM> and the charge accumulation unit <NUM> during the exposure period is accumulated in the bound region. Thus, the amount of charge converted in charge-voltage conversion when the signal SL is read is the total amount of charge in the charge accumulation unit <NUM> and the charge of the FD unit <NUM>.

Note that the signal SL is referred to also as a low-sensitivity data signal SL hereinafter.

Next, the drive signal RST is turned on and the reset gate unit <NUM> is turned on at a time t27. This resets the region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound.

Next, the selection signal SEL is turned off and the selection transistor <NUM> is turned off at a time t28. Thus, the unit pixel <NUM> is not selected.

Next, the drive signal RST is turned off and the reset gate unit <NUM> is turned off at a time t29.

Next, the selection signal SEL is turned on and the selection transistor <NUM> is turned on at a time t30. Thus, the unit pixel <NUM> is selected.

Next, the signal NL based on the potential in the region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound is output via the amplification transistor <NUM> and the selection transistor <NUM> to the vertical signal line <NUM> at a time tb between the time t30 and the time t31. The signal NL is a signal based on the potential in the bound region in which the potential well of the charge accumulation unit <NUM> and the potential well of the FD unit <NUM> are bound when the bound region is reset.

Note that the signal NL is referred to also as a low-sensitivity reset signal NL hereinafter.

Next, the drive signal FCG is turned off and the second transfer gate unit <NUM> is turned off at a time t31.

Next, the signal NH based on the potential of the FD unit <NUM> is output via the amplification transistor <NUM> and the selection transistor <NUM> to the vertical signal line <NUM> at a time tc between the time t31 and the time t32. The signal NH is a signal based on the potential of the FD unit <NUM> when the FD unit <NUM> is reset.

Note that the signal NH is referred to also as a high-sensitivity reset signal NH hereinafter.

Next, the drive signal TGL is turned on and the first transfer gate unit <NUM> is turned on at a time t32. Thus, the charge generated and accumulated in the first opto-electronic converter <NUM> during the exposure period is transferred via the first transfer gate unit <NUM> to the FD unit <NUM>.

Next, the drive signal TGL is turned off and the first transfer gate unit <NUM> is turned off at a time t33. This stops the transfer of the charge from the first opto-electronic converter <NUM> to the FD unit <NUM>.

Next, the signal SH based on the potential of the FD unit <NUM> is output via the amplification transistor <NUM> and the selection transistor <NUM> to the vertical signal line <NUM> at a time td between the time t33 and the time t34. The signal SH is a signal based on the charge generated and accumulated in the first opto-electronic converter <NUM> during the exposure period.

Additionally, the signal SH is based on the potential in the FD unit <NUM> when the charge accumulated in the first opto-electronic converter <NUM> during the exposure period is accumulated in the FD unit <NUM>. Thus, the amount of the charge converted in charge-voltage conversion when the signal SH is read is the amount of charge in the FD unit <NUM>. The amount of charge is smaller than the amount of charge when the low-sensitivity data signal SL is read at the time ta.

Note that the signal SH is referred to also as a high-sensitivity data signal SH hereinafter.

Next, the selection signal SEL is turned off and the selection transistor <NUM> is turned off at a time t34. Thus, the unit pixel <NUM> is not selected.

Next, the horizontal synchronization signal XHS is input and the readout period in which the pixel signal of the unit pixel <NUM> is read is completed at a time t35.

The low-sensitivity data signal SL, the low-sensitivity reset signal NL, the high-sensitivity reset signal NH, and the high-sensitivity data signal SH are output from the unit pixel <NUM> to the vertical signal line <NUM> in this order. Then, in signal processing units placed downstream, for example, the column processing unit <NUM> and signal processing unit <NUM> illustrated in <FIG>, the low-sensitivity data signal SL, the low-sensitivity reset signal NL, the high-sensitivity reset signal NH, and the high-sensitivity data signal SH are processed in predetermined noise removal process and signal process. An exemplary noise removal process performed in the column processing unit <NUM> placed downstream and an exemplary arithmetic process performed in the signal processing unit <NUM> placed downstream will be described hereinafter.

First, a noise removal process that the column processing unit <NUM> performs will be described.

First, an exemplary noise removal process will be described.

The column processing unit <NUM> generates a low-sensitivity differential signal SNL by taking the difference between the low-sensitivity data signal SL and the low-sensitivity reset signal NL. Thus, the low-sensitivity differential signal SNL = the low-sensitivity data signal SL - the low-sensitivity reset signal NL holds.

Next, the column processing unit <NUM> generates a high-sensitivity differential signal SNH by taking the difference between the high-sensitivity data signal SH and the high-sensitivity reset signal NH. Thus, the high-sensitivity differential signal SNH = the high-sensitivity data signal SH - the high-sensitivity reset signal NH holds.

As described above, the low-sensitivity signals SL and NL are processed in a DDS process in which fixed pattern noise specific to a pixel, for example, the variations in the threshold of the amplification transistor in the pixel is removed but reset noise is not removed. The high-sensitivity signals SH and NH is processed in a CDS process in which reset noise and fixed pattern noise specific to a pixel, for example, the variations in the threshold of the amplification transistor in the pixel are removed.

An exemplary arithmetic process of a pixel signal will be described hereinafter.

When the low-sensitivity differential signal SNL is in a predetermined range, the signal processing unit <NUM> calculates the proportion of the low-sensitivity differential signal SNL to the high-sensitivity differential signal SNH as gain by pixel, by a plurality of pixels, by color, by specific pixel in a shared pixel unit, or evenly in all pixels, and generates a gain table. Then, the signal processing unit <NUM> calculates the product of the low-sensitivity differential signal SNL and the gain table as the correction value of the low-sensitivity differential signal SNL.

In this example, the gain is G and the value of the corrected low-sensitivity differential signal SNL (hereinafter, referred to as a corrected low-sensitivity differential signal) is SNL'. The gain G and the corrected low-sensitivity differential signal SNL' can be found with the following expressions (<NUM>) and (<NUM>). <MAT> <MAT>.

In this example, Cfd is the value of the capacity of the FD unit <NUM>, and Cfc is the value of the capacity of the charge accumulation unit <NUM>. Thus, the gain G is equivalent to the proportion of the capacity of the FD unit <NUM> to the capacity of the charge accumulation unit <NUM>.

<FIG> illustrates the relationship between the amount of incident light and each of the low-sensitivity differential signal SNL, the high-sensitivity differential signal SNH, and the corrected low-sensitivity differential signal SNL'.

Next, the signal processing unit <NUM> uses a predetermined threshold Vt illustrated in <FIG>. In terms of a photo-response characteristic, the threshold Vt is set in a region before the signal processing unit <NUM> is saturated with the high-sensitivity differential signal SNH and in which the photo-response characteristic is linear.

Then, when the high-sensitivity differential signal SNH does not exceed the predetermined threshold Vt, the signal processing unit <NUM> outputs the high-sensitivity differential signal SNH as the pixel signal SN of the pixel to be processed. In other words, when SNH < Vt holds, the pixel signal SN = the high-sensitivity differential signal SNH holds.

On the other hand, when the high-sensitivity differential signal SNH exceeds the predetermined threshold Vt, the signal processing unit <NUM> outputs the corrected low-sensitivity differential signal SNL' of the low-sensitivity differential signal SNL as the pixel signal SN of the pixel to be processed. In other words, when Vt ≦ SNH holds, the pixel signal SN = the corrected low-sensitivity differential signal SNL' holds.

By the arithmetic process described above, the signal at a low light condition can smoothly be switched to the signal at a high light condition.

Additionally, providing the charge accumulation unit <NUM> in the low-sensitivity second opto-electronic converter <NUM> in the CMOS image sensor <NUM> can raise the level at which the second opto-electronic converter <NUM> is saturated with the low-sensitivity data signal SL. Thus, while the minimum value of the dynamic range is maintained, the maximum value of the dynamic range can be increased. This can extend the dynamic range.

For example, LED flicker sometimes occurs in an in-vehicle image sensor. The LED flicker is a phenomenon in which an image of an object flickering such as an LED light source is not captured depending on the time when the object flickers. The LED flicker occurs, for example, because the dynamic range of an image sensor in the past is narrow and it is necessary to adjust the exposure period for each object.

In other words, to deal with objects in various light conditions, an image sensor in the past increases the exposure period for an object in a low light condition and decreases the exposure period for an object in a high light condition. This enables the image sensor in the past to deal with objects in various light conditions even when the dynamic range of the image sensor is narrow. On the other hand, the image sensor reads the signal at a constant rate regardless of the length of the exposure period. Thus, when the exposure period is set at a unit shorter than the period in which the signal is read, the light entering the opto-electronic converter outside the exposure period is converted into charge in opto-electronic conversion and is destroyed without readout.

On the other hand, the CMOS image sensor <NUM> can extend the dynamic range as described above, and can increase the exposure period. This prevents LED flicker from occurring. Additionally, using the CMOS image sensor <NUM> can prevent an artifact occurring when the number of divided times in a time division scheme or the number of divided spaces in a space division scheme increases, or can prevent the reduction in resolution.

Next, the configuration of the unit pixel <NUM> including the high-sensitivity first opto-electronic converter <NUM> and the low-sensitivity second opto-electronic converter <NUM> as described above will additionally be described. Hereinafter, with reference to cross-sectional views of the unit pixel <NUM>, the configuration of the unit pixel <NUM> will additionally be described.

<FIG> is a cross-sectional view of the unit pixel <NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor. The unit pixel <NUM> illustrated in <FIG> will be referred to as a unit pixel <NUM>-<NUM> hereinafter to indicate that the unit pixel <NUM> illustrated in <FIG> has a first configuration.

In the unit pixel <NUM>-<NUM>, an on-chip lens <NUM>, a colored filter <NUM>, a light-blocking film <NUM>, and a silicon substrate <NUM> are layered from the upper part of the drawing. The first opto-electronic converter <NUM> and the second opto-electronic converter <NUM> are formed in the silicon substrate <NUM>.

Note that, although not illustrated, for example, a glass cover is layered on the on-chip lens <NUM>, and a wiring layer or a supporting substrate is layered under the silicon substrate <NUM>. The parts necessary for the description will be properly illustrated and described while the illustration and description of the other parts will properly be omitted hereinafter.

<FIG> illustrates the first opto-electronic converter <NUM>-<NUM>, the first opto-electronic converter <NUM>-<NUM>, and the second opto-electronic converter <NUM>. Additionally, the on-chip lenses <NUM>-<NUM> to <NUM>-<NUM> are formed on the three opto-electronic converters, respectively.

The light-blocking film <NUM> is formed only on the second opto-electronic converter <NUM>. The light-blocking film <NUM> has a function to absorb or reflect light. The light-blocking film <NUM> can be made of a metal film so that the light-blocking film <NUM> works as a film that reflects light. The light-blocking film <NUM> can be a film that absorbs a part of light and allows a part of the light to pass through the film. Alternatively, the light-blocking film <NUM> can be an optical absorption film that absorbs light.

The light-blocking film <NUM> is, for example, an amorphous silicon film, a polysilicon film, a germanium (Ge) film, a gallium nitride (GaN) film, a cadmium telluride (CdTe) film, a gallium arsenide (GaAs) film, an indium phosphide (InP) film, a CuInSe2 film, a Cu2S film, a CIGS film, a non-conductive carbon film, a black resist film, or an organic opto-electronic conversion film.

Note that the light-blocking film is formed on the second opto-electronic converter <NUM> and the light-blocking film can be made of the materials described above also in second to sixteenth configurations described below. Note that the materials of which the light-blocking film is made are examples. The material of which the light-blocking film is made is not limited to the example materials.

Forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> as described above causes the light-blocking film <NUM> to absorb the light passing through the on-chip lens <NUM>-<NUM> and reduces the light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. This increases the performance of the second opto-electronic converter <NUM> as the low-sensitivity opto-electronic converter. Thus, the dynamic range can be extended.

Next, the second configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> formed on the second opto-electronic converter <NUM> in the unit pixel <NUM>-<NUM> is removed, differently from the unit pixel <NUM>-<NUM>, and the other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>. Hereinafter, the description of the parts similar to the parts of the unit pixel <NUM>-<NUM> will be put with similar reference signs and the descriptions will properly be omitted. Similarly, the descriptions of the other parts will properly be omitted when the other parts are similar to the parts of the unit pixel <NUM>-<NUM>.

The unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> is not formed on the second opto-electronic converter <NUM>. Thus, the light is not collected on the second opto-electronic converter <NUM> and enters the second opto-electronic converter <NUM> and the light entering the second opto-electronic converter <NUM> is reduced. This further reduces the sensitivity of the second opto-electronic converter <NUM> and can extend the dynamic range of the low-sensitivity opto-electronic converter.

Next, the third configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which a light-blocking wall <NUM> is added to the configuration of the unit pixel <NUM>-<NUM>, differently from the unit pixel <NUM>-<NUM>, and the other parts of the unit pixel <NUM>-<NUM> are the same as the parts of the unit pixel <NUM>-<NUM>.

The light-blocking wall <NUM> is provided between pixels. In the unit pixel <NUM>-<NUM> illustrated in <FIG>, the light-blocking walls <NUM> are provided between the first opto-electronic converter <NUM>-<NUM> and the second opto-electronic converter <NUM>, and between the first opto-electronic converter <NUM>-<NUM> and the second opto-electronic converter <NUM>. As describe above, the light-blocking wall <NUM> is provided in a pixel separation region in which the pixels are separate from each other. The light-blocking wall <NUM> can be formed in a trench or groove and can include one or more insulating films extending from the light receiving surface.

The light-blocking walls <NUM> can be formed in trenches from a combination of a negative fixed charge film and an oxide film. The combination can be a combination of a negative fixed charge film, an oxide film, and a metal. Examples of a negative fixed charge film include hafnium oxide and tantalum oxide.

The light-blocking wall <NUM> is used to prevent light leaking from an opto-electronic converter into the opto-electronic converters next to the opto-electronic converter. Providing the light-blocking wall <NUM> can reduce, for example, the occurrence of mixture of colors. In addition, the light-blocking wall <NUM> can prevent light from leaking into a low sensitivity pixel <NUM> from other pixels, and can therefore_help to maintain the accuracy of the unit pixel output.

Also in this configuration, forming a light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> causes the light-blocking film <NUM> to absorb the light passing through the on-chip lens <NUM>-<NUM> and reduces the light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. Thus, the dynamic range can be extended. Providing the light-blocking wall <NUM> can reduce, for example, the occurrence of mixture of colors.

Next, the fourth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which a light-blocking wall <NUM> is added to the configuration of the unit pixel <NUM>-<NUM>, differently from the unit pixel <NUM>-<NUM>, and the other parts, for example, the second opto-electronic converter <NUM> without the on-chip lens <NUM>-<NUM> in the unit pixel <NUM>-<NUM> are the same as the parts of the unit pixel <NUM>-<NUM>. Additionally, the configuration to which the light-blocking wall <NUM> is added is the same as the configuration of the unit pixel <NUM>-<NUM> illustrated in <FIG>.

Also in this configuration, forming a light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> causes the light-blocking film <NUM> to absorb the light entering the light-blocking film <NUM> and reduces the light entering the second opto-electronic converter <NUM>. Additionally, an on-chip lens is not formed. This further reduces the amount of light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. Thus, the dynamic range of the low-sensitivity opto-electronic converter can be extended. Providing the light-blocking wall <NUM> can reduce, for example, the occurrence of mixture of colors.

Next, the fifth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which a light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a different shape from the light-blocking film <NUM> of the unit pixel <NUM>-<NUM>, differently from the unit pixel <NUM>-<NUM>, and the other parts are the same as the parts of the unit pixel <NUM>-<NUM>. The light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit. The light-blocking film <NUM> is not necessarily formed on the slit of the light-blocking film <NUM>. Alternatively, the light-blocking film <NUM> at the slit can be thinner than light-blocking film <NUM> at parts other than the slit.

Forming a slit on the light-blocking film <NUM> can cause the second opto-electronic converter <NUM> to work as a polarization pixel.

For example, when the second opto-electronic converter <NUM> is installed on a vehicle and captures an image including the surface of a road, the light reflected on the surface of the road is a polarized light in parallel to the surface of the road. To capture an image from which such a polarized light is removed, a slit is formed on the light-blocking film <NUM> in a direction parallel to the surface of the road. This can selectively block the light reflected on the surface of the road and can receive the light from the other objects.

Forming a slit on the light-blocking film <NUM> as described above can reduce the light entering the second opto-electronic converter <NUM> and also can remove unnecessary light.

When the light-blocking film <NUM> is used also as a polarizer as described above, the light-blocking film <NUM> can be made of metal in addition to the materials described above. Note that using the light-blocking film as the polarizer can effectively reduce the direct or indirect light in comparison with using a polarizer made of metal.

Also in this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> reduces the amount of light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

Next, the sixth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a different shape from the light-blocking film <NUM> of the unit pixel <NUM>-<NUM>, differently from the unit pixel <NUM>-<NUM>, and the other parts, for example, the second opto-electronic converter <NUM> without the on-chip lens <NUM>-<NUM> in the unit pixel <NUM>-<NUM> are the same as the parts of the unit pixel <NUM>-<NUM>. The light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

Forming a slit on the light-blocking film <NUM> can reduce the light entering the second opto-electronic converter <NUM> and also can remove unnecessary light, similarly to the unit pixel <NUM>-<NUM> (<FIG>).

Also in this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> reduces the amount of light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range. Additionally, an on-chip lens is not formed on the second opto-electronic converter <NUM>. This further reduces the amount of light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

Next, the seventh configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the light-blocking film <NUM> has a slit, differently from the unit pixel <NUM>-<NUM>, and the other parts, for example, the light-blocking film <NUM> provided between pixels in the unit pixel <NUM>-<NUM> are the same as the parts of the unit pixel <NUM>-<NUM>.

Also in this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> reduces the light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light. Providing the light-blocking wall <NUM> can reduce, for example, the occurrence of mixture of colors.

Next, the eighth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a backside-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the light-blocking film <NUM> has a slit, differently from the unit pixel <NUM>-<NUM>, and the other parts, for example, the light-blocking film <NUM> provided between pixels in the unit pixel <NUM>-<NUM> and the second opto-electronic converter <NUM> without an on-chip lens are the same as the parts of the unit pixel <NUM>-<NUM>.

Also in this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> reduces the light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range. Additionally, an on-chip lens is not formed on the second opto-electronic converter <NUM>. This further reduces the light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range.

Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light. Providing the light-blocking wall <NUM> can reduce, for example, the occurrence of mixture of colors.

<FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor.

In the unit pixel <NUM>-<NUM> illustrated in <FIG>, an on-chip lens <NUM>, a colored filter <NUM>, a light-blocking film <NUM>, a wiring layer <NUM>, and a silicon substrate <NUM> are layered from the upper part of the drawing. A first opto-electronic converter <NUM> and a second opto-electronic converter <NUM> are formed in the silicon substrate <NUM>.

Note that, although not illustrated in the drawing, for example, a glass cover is layered on the on-chip lens <NUM>. The parts necessary for the description will properly be illustrated and additionally described while the illustration and description of the other parts will properly be omitted.

<FIG> illustrates the first opto-electronic converter <NUM>-<NUM>, the first opto-electronic converter <NUM>-<NUM>, and the second opto-electronic converter <NUM>. Additionally, on-chip lenses <NUM>-<NUM> to <NUM>-<NUM> are formed on the three opto-electronic converters, respectively.

The light-blocking film <NUM> is formed only on the second opto-electronic converter <NUM>. The light-blocking film <NUM> is, for example, an amorphous silicon film, a polysilicon film, a Ge film, a GaN film, a CdTe film, a GaAs film, an InP film, a CuInSe2 film, Cu2S, a CIGS film, a non-conductive carbon film, a black resist film, or an organic opto-electronic conversion film. Additionally, when the light-blocking film <NUM> has a slit as described below, the light-blocking film <NUM> can be made of metal. Note that the materials of which the light-blocking film is made are examples and the material of which the light-blocking film is made is not limited to the example materials.

Also in the front-side illumination image sensor as described above, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> causes the light-blocking film <NUM> to absorb the light passing through the on-chip lens <NUM>-<NUM> and reduces the light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. Thus, the dynamic range can be extended.

Next, the tenth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> formed on the second opto-electronic converter <NUM> in the unit pixel <NUM>-<NUM> is removed, differently from the unit pixel <NUM>-<NUM>, and the other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>.

The on-chip lens <NUM>-<NUM> is not formed on the second opto-electronic converter <NUM>. This causes the light to enter the second opto-electronic converter <NUM> without being collected. This reduces the light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity of the second opto-electronic converter <NUM> can extend the dynamic range.

Next, the eleventh configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the light-blocking film <NUM> is formed on the upper side of the wiring layer <NUM> (the side facing the on-chip <NUM>) in the drawing in the unit pixel <NUM>-<NUM> while the light-blocking film is formed on the lower side of the wiring layer <NUM> (the side facing the silicon substrate <NUM>) in the drawing in the unit pixel <NUM>-<NUM>. The other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>.

With reference to <FIG> again, the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> is formed on the upper side of the wiring layer <NUM> and in the colored filter <NUM>. On the other hand, the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> illustrated in <FIG> is formed on the lower side of the wiring layer <NUM> and in the wiring layer <NUM> on the silicon substrate <NUM>. As described above, the light-blocking film can be formed on the upper or lower side of the wiring layer <NUM>.

As described above, also in a front-side illumination image sensor, the light-blocking film <NUM> is formed on the low-sensitivity second opto-electronic converter <NUM>. This causes the light-blocking film <NUM> to absorb the light passing through the on-chip lens <NUM>-<NUM> and reduces the light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. Thus, the dynamic range can be extended.

Next, the twelfth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> formed on the second opto-electronic converter <NUM> in the unit pixel <NUM>-<NUM> is removed, differently from the unit pixel <NUM>-<NUM> and the other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>.

The on-chip lens <NUM>-<NUM> is not formed on the second opto-electronic converter <NUM>. Thus, light is not collected on the second opto-electronic converter <NUM> and enters the second opto-electronic converter <NUM>. This reduces the light entering the second opto-electronic converter <NUM>. Thus lowering the sensitivity of the second opto-electronic converter <NUM> and extending the dynamic range.

Next, the thirteenth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a different shape from the light-blocking film <NUM> of the unit pixel <NUM>-<NUM>, differently from the unit pixel <NUM>-<NUM>, and the other parts of the unit pixel <NUM>-<NUM> are the same as the parts of the unit pixel <NUM>-<NUM>. The light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit shape and formed in the layer of the colored filter <NUM>.

Forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer and the second opto-electronic converter <NUM> to a polarization pixel.

Also in this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> reduces the light entering the second opto-electronic converter <NUM>. Thus lowering the sensitivity, which can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

Next, the fourteenth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> formed on the second opto-electronic converter <NUM> in the unit pixel <NUM>-<NUM> is removed, differently from the unit pixel <NUM>-<NUM> and the other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>. The light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit, and formed in the layer of the colored filter <NUM>.

The on-chip lens <NUM>-<NUM> is not formed on the second opto-electronic converter <NUM>. Thus, light is not collected on the second opto-electronic converter <NUM> and enters the second opto-electronic converter <NUM>. This reduces the light entering the second opto-electronic converter <NUM>. This further reduces the sensitivity of the second opto-electronic converter <NUM>. Thus, the dynamic range can be extended. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

Next, the fifteenth configuration of the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the light-blocking film <NUM> is formed on the upper side of the wiring layer <NUM> in the drawing in the unit pixel <NUM>-<NUM> while the light-blocking film <NUM> is formed on the lower side of the wiring layer <NUM> in the drawing in the unit pixel <NUM>-<NUM>. The other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>. In other words, the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit, and is formed on the lower side of the wiring layer <NUM> in the drawing in the unit pixel <NUM>-<NUM>.

Also in the front-side illumination image sensor having this configuration, forming the light-blocking film <NUM> on the low-sensitivity second opto-electronic converter <NUM> causes the light-blocking film <NUM> to absorb the light passing through the on-chip lens <NUM>-<NUM> and reduces the light entering the second opto-electronic converter <NUM>. Thus lowering the sensitivity of the second opto-electronic converter <NUM>, which can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

Next, the sixteenth configuration in the unit pixel <NUM> will be described. <FIG> is a cross-sectional view of a unit pixel <NUM>-<NUM> when the CMOS image sensor <NUM> is a front-side-illumination image sensor, similarly to the unit pixel <NUM>-<NUM> illustrated in <FIG>.

In comparison between the unit pixel <NUM>-<NUM> illustrated in <FIG> and the unit pixel <NUM>-<NUM> illustrated in <FIG>, the unit pixel <NUM>-<NUM> has a configuration in which the on-chip lens <NUM>-<NUM> formed on the second opto-electronic converter <NUM> in the unit pixel <NUM>-<NUM> is removed, differently from the unit pixel <NUM>-<NUM> and the other parts in the unit pixel <NUM>-<NUM> are the same as the parts in the unit pixel <NUM>-<NUM>. In other words, the light-blocking film <NUM> of the unit pixel <NUM>-<NUM> has a slit and is formed on the lower side of the wiring layer <NUM>.

The on-chip lens <NUM>-<NUM> is not formed on the second opto-electronic converter <NUM>. Thus, light is not collected on the second opto-electronic converter <NUM> and enters the second opto-electronic converter <NUM>. This reduces the light entering the second opto-electronic converter <NUM>. Thus lowering the sensitivity of the second opto-electronic converter <NUM>, which can extend the dynamic range. Additionally, forming a slit on the light-blocking film <NUM> can cause the light-blocking film <NUM> to work as a polarizer so as to remove the effect of unnecessary light such as the reflected light.

As described in the first to sixteenth configurations, a film having a function to absorb light is formed on the low-sensitivity second opto-electronic converter <NUM>. This reduces the amount of light entering the second opto-electronic converter <NUM>. Thus, lowering the sensitivity can extend the dynamic range.

Additionally, forming a slit on the light-blocking film can cause the light-blocking film to work as a polarizer. Providing the polarizer removes the effect of the reflected light (the effect of unnecessary light) and simultaneously, lowering the sensitivity, which can extend the dynamic range.

Using the light-blocking film as the polarizer can effectively reduce the direct or indirect light in comparison with using a polarizer made of metal.

The unit pixels <NUM>, each of which includes a first opto-electronic converter <NUM> and a second opto-electronic converter <NUM>, are arranged, for example, as illustrated in <FIG>. In <FIG>, the unit pixels are referred to as unit pixels <NUM>. A unit pixel <NUM> will be described as one of the unit pixels <NUM>-<NUM> to <NUM>-<NUM>.

<FIG> illustrates an example in which (four by four) <NUM> unit pixels <NUM>-<NUM> to <NUM>-<NUM> are arranged. Each unit pixel <NUM> includes a first opto-electronic converter <NUM> and a second opto-electronic converter <NUM>. For example, the unit pixel <NUM>-<NUM> includes a first opto-electronic converter <NUM>-<NUM> and a second opto-electronic converter <NUM>-<NUM>.

The first opto-electronic converter <NUM> and the second opto-electronic converter <NUM> have different sensitivities depending on the size of the light-receiving surface. In other words, as illustrated in <FIG>, the light-receiving surface of the first opto-electronic converter <NUM> is larger than the light-receiving surface of the second opto-electronic converter <NUM>.

In the example of <FIG>, for example, the second opto-electronic converter <NUM>-<NUM> of a unit pixel is placed on the right and obliquely lower side of the first opto-electronic converter <NUM>-<NUM> of that unit pixel. Although not illustrated, the second opto-electronic converter <NUM>-<NUM> can be placed on the right side of the first opto-electronic converter <NUM>-<NUM>. Alternatively, the positional relationship between the second opto-electronic converter <NUM>-<NUM> and the first opto-electronic converter <NUM>-<NUM> can be different from the above. For example, at least a portion of a side of the second opto-electronic converter <NUM>-<NUM> can coincide with or can be adjacent to a portion of a side of the first opto-electronic converter <NUM>-<NUM>.

In the unit pixel <NUM>, for example, a signal process circuit can be placed at a part at which the first opto-electronic converter <NUM> and the second opto-electronic converter <NUM> are not arranged. In other words, arranging the first opto-electronic converter <NUM> and second opto-electronic converter <NUM> with different light-receiving areas causes an excessive region in the unit pixel <NUM>. However, placing, for example, a signal process circuit in the excessive region can effectively use the excessive region.

The colors of the colored filters <NUM> (<NUM>) placed on the unit pixels <NUM> can be arranged, for example, in Bayer arrangement. As illustrated in <FIG>, the unit pixel <NUM>-<NUM> can be red (R), the unit pixel <NUM>-<NUM> can be green (G), the unit pixel <NUM>-<NUM> can be green (G), and the unit pixel <NUM>-<NUM> can be blue (B).

In the color arrangement described above, with reference to <FIG> and <FIG> again, for example, the first opto-electronic converter <NUM>-<NUM> and the second opto-electronic converter <NUM>-<NUM> are arranged and the color of the colored filter <NUM> (or <NUM>, hereinafter, the colored filter <NUM> is cited as an example for the description) is red (R) in the unit pixel <NUM>-<NUM>. As described above, the first opto-electronic converter <NUM> and second opto-electronic converter <NUM> arranged in the same unit pixel <NUM> have the color of the same colored filter <NUM>.

As illustrated in <FIG>, the colors can be arranged in Bayer arrangement in which four pixels have the same color. In <FIG>, the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, and the unit pixel <NUM>-<NUM> are red (R); the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, and the unit pixel <NUM>-<NUM> are green (G); the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, and the unit pixel <NUM>-<NUM> are green (G); and the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, the unit pixel <NUM>-<NUM>, and the unit pixel <NUM>-<NUM> are green (G).

In this example, Bayer arrangement is cited as an example of the color arrangement. However, the present technology can be used for another color arrangement.

A light-blocking film is formed on the second opto-electronic converter <NUM> as described above. The light-blocking film is the light-blocking film <NUM> without a slit illustrated, for example, in <FIG> (hereinafter, referred to as a solid light-blocking film <NUM>), or the light-blocking film <NUM> with a slit illustrated, for example, in <FIG>.

Note that, although the light-blocking film <NUM> (<FIG>) will be cited as an example of the solid light-blocking film for the description hereinafter, the description can be applied to the light-blocking film <NUM> (<FIG>) and the light-blocking film <NUM> (<FIG>). Additionally, the light-blocking film <NUM> (<FIG>) will be cited as an example of the slit light-blocking film for the description hereinafter. However, the description can be applied to the light-blocking film <NUM> (<FIG>) and the light-blocking film <NUM> (<FIG>).

When the solid light-blocking films <NUM> are formed on the unit pixel, the light-blocking film <NUM> are formed, for example, as illustrated in <FIG> only illustrates left and upper four pixels among the (four by four) <NUM> unit pixels <NUM>-<NUM> to <NUM>-<NUM> illustrated in <FIG>. However, the light-blocking films <NUM> are similarly formed on the other pixels.

As illustrated in <FIG>, the solid light-blocking films <NUM> are formed on the second opto-electronic converters <NUM> in the unit pixels <NUM>. For example, the second opto-electronic converter <NUM> is formed on the right and lower side of the unit pixel <NUM>-<NUM> illustrated in <FIG>, and a light-blocking film <NUM>-<NUM> is formed in the region in which the second opto-electronic converter <NUM>-<NUM> is formed.

Note that, as illustrated in <FIG>, the light-blocking film <NUM> can be formed so that the light-blocking film <NUM> is connected to a well (WELL) in an outer peripheral region of the pixel.

When the slit light-blocking films <NUM> are formed on the unit pixels, the light-blocking film <NUM> are formed, for example, as illustrated in <FIG>. As illustrated in <FIG>, the slit light-blocking films <NUM> are formed on the second opto-electronic converters <NUM> in the unit pixels <NUM>, respectively.

The slits illustrated in <FIG> extend in the lateral direction of the drawing and all the four pixels have slits extending in the same direction. As described above, the slits on the light-blocking films <NUM> provided on the second opto-electronic converters <NUM> can be formed in the same direction.

According to the invention, the direction in which the slits are arranged on the light-blocking films <NUM> can be varied depending on the pixel. <FIG> illustrates that the light-blocking films <NUM> are formed on the second opto-electronic converters <NUM> in the unit pixels <NUM>, respectively, and the slits of the light-blocking films <NUM> with slits are formed in different directions depending on the pixel.

The slits on the light-blocking film <NUM>-<NUM> formed on the second opto-electronic converter <NUM>-<NUM> in the unit pixel <NUM>-<NUM> illustrated in <FIG> are formed in the lateral direction of the drawing. The slits on the light-blocking film <NUM>-<NUM> formed on the second opto-electronic converter <NUM>-<NUM> in the unit pixel <NUM>-<NUM> are formed in a direction toward the left and obliquely toward the lower side of the drawing.

The slits on the light-blocking film <NUM>-<NUM> formed on the second opto-electronic converter <NUM>-<NUM> in the unit pixel <NUM>-<NUM> are formed in a direction toward the right and obliquely toward the lower side of the drawing. The slits on the light-blocking film <NUM>-<NUM> formed on the second opto-electronic converter <NUM>-<NUM> in the unit pixel <NUM>-<NUM> are formed in the longitudinal direction of the drawing.

In the example illustrated in <FIG>, the slits are formed in the four directions. Similarly, in the other pixels (not illustrated), the slits are formed on the light-blocking films <NUM> so that the slits are formed in four different directions in (two by two) four pixels depending on the pixel. Note that, although the four directions are cited as an example in this example, another direction can be added or, for example, the slits can be formed in two or three directions. The number of directions in which the slits are formed on the light-blocking films <NUM> are not limited to four.

Forming the slits in different directions pixel by pixel as described above, in other words, varying the directions in which the slits are formed on the light-blocking films <NUM> formed on the adjacent second opto-electronic converters <NUM> pixel by pixel can block the polarized light from different directions.

Additionally, when the direction in which the slits are formed varies depending on the pixel as described above, for example, when the slits are formed in different directions in the four pixels illustrated in <FIG>, respectively, the four unit pixels can have the same color. In other words, the colors can be arranged in Bayer arrangement in which the four pixels have the same color as illustrated in <FIG>, and the slits can be formed in different directions in the four pixels having the same color, respectively.

An example in which two opto-electronic converters with different sensitivities are arranged in a pixel has been described above. However, three or more opto-electronic converters with different sensitivities can be arranged in a pixel. The difference of the sensitivities can be adjusted by changing the material or thickness of the light-blocking film.

Additionally, an example in which the present technology is applied to a CMOS image sensor having unit pixels arranged in rows and columns has been described in the embodiments. However, the application of the present technology is not limited to the application to a CMOS image sensor. In other words, the present technology can be applied to all of image pick-up apparatuses in which unit pixels are two-dimensionally in rows and columns in an X-Y address scheme.

Furthermore, the present technology can be applied not only to an image pick-up apparatus that detects the distribution of visible incident lights and captures the lights as an image but also to all the image pick-up apparatuses that capture the distribution of incoming infrared rays, X-rays, or particles as an image.

Note that the image pick-up apparatus can be formed as a chip, or can be formed as a module having an image pick-up function in which an image pick-up unit and a signal processing unit or an optical system are packaged.

<FIG> is a diagram of exemplary uses of the image pick-up apparatus.

The image pick-up apparatus can be used for various purposes in which lights including visible lights, infrared rays, ultraviolet lights, or X rays are sensed as described below.

<FIG> is a block diagram of an exemplary configuration of an image pick-up apparatus (camera device) <NUM> that is an exemplary electronic device using the present technology.

As illustrated in <FIG>, the image pick-up apparatus <NUM> includes, for example, an optical system including a lens group <NUM>, an image pick-up element <NUM>, a DSP <NUM> that is a camera signal processing unit, a frame memory <NUM>, a display device <NUM>, a recording device <NUM>, an operation system <NUM>, and a power-supply system <NUM>. The DSP <NUM>, the frame memory <NUM>, the display device <NUM>, the recording device <NUM>, the operation system <NUM>, and the power-supply system <NUM> are connected to each other via a bus line <NUM>.

The lens group <NUM> captures the incident light (image light) from an object and forms an image on the image pick-up surface of the image pick-up element <NUM>. The image pick-up element <NUM> converts the amount of incident light with which the lens group <NUM> forms an image on the image pick-up surface into electric signals pixel by pixel so as to output the electric signals as pixel signals.

The display device <NUM> includes a panel display device such as a liquid crystal display device or an organic electro luminescence (EL) display device so as to display the video or still image captured by the image pick-up element <NUM>. The recording device <NUM> records the video or still image captured by the image pick-up element <NUM> onto a recording medium such as a memory card, a videotape, or a Digital Versatile Disk (DVD).

The operation system <NUM> issues instructions for the operation of various functions of the image pick-up apparatus <NUM> under the control by the user. The power-supply system <NUM> properly supplies various power sources as the power sources of the operation of the DSP <NUM>, the frame memory <NUM>, the display device <NUM>, the recording device <NUM>, and the operation system <NUM>.

The image pick-up apparatus <NUM> described above is applied to a video camera, or a digital still camera, additionally, to a camera module for a mobile device such as a smartphone, or a mobile phone. The image pick-up apparatus <NUM> can use the image pick-up apparatus described in each of the embodiments described above as the image pick-up element <NUM>. This can improve the image quality of images captured by the image pick-up apparatus <NUM>.

Claim 1:
An imaging device (<NUM>), comprising:
a substrate (<NUM>), on which a pixel array including a plurality of unit pixels is arranged, each of the unit pixels includes:
a first opto-electronic converter (<NUM>) having a first area formed in the substrate (<NUM>);
a second opto-electronic converter (<NUM>) having a sensitivity lower than a sensitivity of the first opto-electronic converter (<NUM>) and having a second area formed in the substrate (<NUM>), wherein the first area is larger than the second area;
a trench extending from a first surface of the substrate (<NUM>), wherein at least a portion of the trench is between the first opto-electronic converter (<NUM>) and the second opto-electronic converter (<NUM>), and
wherein a light blocking wall (<NUM>) is formed in the trench and includes an insulating film extending from the first surface of the substrate (<NUM>); or includes at least one of a negative fixed charge film, an oxide film, and a metal; and
a light-blocking film (<NUM>; <NUM>), wherein the light-blocking film (<NUM>; <NUM>) is formed over at least a portion of the second area of the second opto-electronic converter (<NUM>),
wherein the light-blocking film (<NUM>; <NUM>) absorbs a portion of light incident on the imaging device (<NUM>), and
wherein the light-blocking film (<NUM>) includes a slit, wherein the directions in which the slits in the plurality of the unit pixels are formed on the light-blocking films (<NUM>) formed on the adjacent second opto-electronic converters (<NUM>) of adjacent pixels are different.