JP2023174479A - Photoelectric conversion device - Google Patents

Abstract

To provide a photoelectric conversion device that has an expanded dynamic range.SOLUTION: A photoelectric conversion device has: a first photoelectric conversion unit; a second photoelectric conversion unit that has a lower sensitivity than that of the first photoelectric conversion unit; a floating diffusion unit to which electric charges generated in the first photoelectric conversion unit and the second photoelectric conversion unit are transferred; a first transfer electrode that transfers the electric charges from the first photoelectric conversion unit to the floating diffusion unit; a second transfer electrode that transfers the electric charges from the second photoelectric conversion unit to the floating diffusion unit; and a first control electrode that controls the potential between the first photoelectric conversion unit and the second photoelectric conversion unit so as to allow the electric charges to move between the first photoelectric conversion unit and the second photoelectric conversion unit.SELECTED DRAWING: Figure 4

Description

The present invention relates to a photoelectric conversion device.

In recent years, there has been a demand for expanding the dynamic range of photoelectric conversion devices. For example, in applications such as in-vehicle cameras and security cameras, a photoelectric conversion device with an expanded dynamic range can suitably capture images even in environments where there is a large difference in brightness and darkness due to backlighting or the like.

One method for expanding the dynamic range is a technique of combining multiple photodiodes with different characteristics. Patent Documents 1 to 4 disclose examples of photoelectric conversion devices including a plurality of photodiodes having mutually different characteristics.

Japanese Patent Application Publication No. 2003-218343 JP2007-329721A US Patent Application Publication No. 2018/0269245 US Patent Application Publication No. 2019/0131333

In a photoelectric conversion device including a plurality of photodiodes having mutually different characteristics as described in Patent Documents 1 to 4, further expansion of the dynamic range may be required depending on the application.

An object of the present invention is to provide a photoelectric conversion device that can further expand the dynamic range.

According to one disclosure of the present specification, a first photoelectric conversion section, a second photoelectric conversion section having lower sensitivity than the first photoelectric conversion section, and the first photoelectric conversion section and the second photoelectric conversion section a floating diffusion section to which generated charges are transferred; a first transfer electrode that transfers charges from the first photoelectric conversion section to the floating diffusion section; and a floating diffusion section that transfers charges from the second photoelectric conversion section to the floating diffusion section. A potential between the first photoelectric conversion section and the second photoelectric conversion section is set so that charges can be transferred between the second transfer electrode and the first photoelectric conversion section and the second photoelectric conversion section. A photoelectric conversion device characterized by having a first control electrode for controlling the photoelectric conversion device is provided.

According to the present invention, a photoelectric conversion device that can further expand the dynamic range is provided.

FIG. 1 is a block diagram showing a schematic configuration of a photoelectric conversion device according to a first embodiment. FIG. 3 is an equivalent circuit diagram of a pixel according to the first embodiment. FIG. 2 is a schematic plan view of a pixel according to the first embodiment. FIG. 2 is a schematic cross-sectional view of a pixel according to the first embodiment. FIG. 3 is a diagram schematically showing the potential within a pixel according to the first embodiment. 3 is a graph schematically showing the relationship between illuminance and SNR according to the first embodiment. FIG. 7 is a schematic plan view of a pixel according to a second embodiment. FIG. 7 is a schematic cross-sectional view of a pixel according to a third embodiment. FIG. 7 is a schematic plan view of a pixel according to a fourth embodiment. FIG. 7 is a schematic cross-sectional view of a pixel according to a fourth embodiment. FIG. 3 is a block diagram of a device according to a fifth embodiment. FIG. 3 is a block diagram of a device according to a sixth embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Identical or corresponding elements are denoted by common reference numerals throughout multiple drawings, and their description may be omitted or simplified.

In the first to third embodiments described below, an imaging device will be mainly described as an example of a photoelectric conversion device. However, the photoelectric conversion device in each embodiment is not limited to an imaging device, and can be applied to other devices as well. Examples of other devices include distance measuring devices and photometric devices. The distance measuring device may be, for example, a focus detection device, a distance measuring device using TOF (Time-Of-Flight), or the like. The photometric device may be a device that measures the amount of light incident on the device. Further, although it is assumed that a PN junction type photodiode is used in the photoelectric conversion section in each embodiment, a SPAD (Single Photon Avalanche Diode) may be used.

[First embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a photoelectric conversion device according to this embodiment. The photoelectric conversion device of this embodiment includes a pixel array 1, a vertical scanning circuit 2, a column readout circuit 3, a horizontal scanning circuit 4, an output circuit 5, and a control circuit 6. A circuit that constitutes a photoelectric conversion device may be formed on one or more semiconductor substrates.

The pixel array 1 has a plurality of pixels 10 arranged in a plurality of rows and a plurality of columns. Each of the plurality of pixels 10 photoelectrically converts incident light to generate charges, and outputs a signal corresponding to the incident light.

In each row of the pixel array 1, a plurality of control lines 11 are arranged extending in a first direction (horizontal direction in FIG. 1). Each of the plurality of control lines 11 is connected to the pixels 10 arranged in the first direction, and serves as a common signal line for these pixels 10. The first direction in which the control lines 11 extend is sometimes referred to as the row direction or horizontal direction. The control line 11 is connected to the vertical scanning circuit 2.

In each column of the pixel array 1, an output line 12 is arranged extending in a second direction (vertical direction in FIG. 1) intersecting the first direction. Each of the output lines 12 is connected to the pixels 10 arranged in the second direction, and serves as a common signal line for these pixels 10. The second direction in which the output lines 12 extend is sometimes referred to as the column direction or the vertical direction. Each of the output lines 12 is connected to a current source 13 and a column readout circuit 3, which will be described later in FIG.

The control circuit 6 outputs control signals such as a vertical synchronization signal, a horizontal synchronization signal, and a clock signal to the vertical scanning circuit 2, column readout circuit 3, and horizontal scanning circuit 4. Thereby, the control circuit 6 controls the operation of these circuits.

The vertical scanning circuit 2 is a scanning circuit including logic circuits such as a shift register, a gate circuit, and a buffer circuit. The vertical scanning circuit 2 outputs a control signal to the pixel 10 via the control line 11 based on a vertical synchronization signal, a horizontal synchronization signal, a clock signal, etc., and performs scanning in which the pixel 10 sequentially outputs a signal row by row. . Further, the vertical scanning circuit 2 controls the charge accumulation period in the pixel 10.

The signal generated by the pixel 10 is output to the column readout circuit 3 via the output line 12 of the corresponding column. The column readout circuit 3 has column circuits corresponding to each column. The column circuit performs processing such as amplification and analog-to-digital conversion on the signal input via the output line 12, and holds the processed signal for each column.

The horizontal scanning circuit 4 is a scanning circuit including logic circuits such as a shift register, a gate circuit, and a buffer circuit. The horizontal scanning circuit 4 sequentially selects a plurality of column circuits of the column readout circuit 3. As a result, each of the plurality of column circuits sequentially outputs the held signals to the output circuit 5. The output circuit 5 outputs a signal to the outside of the photoelectric conversion device in a predetermined format.

FIG. 2 is an equivalent circuit diagram of the pixel 10 according to this embodiment. In the following description, it is assumed that the charges accumulated by the photoelectric conversion section within the pixel 10 are electrons. Further, it is assumed that all transistors included in the pixel 10 are N-type MOS transistors. However, the charges accumulated by the photoelectric conversion section may be holes, and in this case, the transistor of the pixel 10 may be a P-type MOS transistor. In other words, the conductivity type of a transistor or the like can be changed as appropriate depending on the polarity of the charge treated as a signal.

The pixel 10 includes photoelectric conversion units PDA, PDB, and PDC, transfer transistors M1A, M1B, and M1C, a reset transistor M2, an amplification transistor M3, a selection transistor M4, and element connection transistors M5 and M6. The photoelectric conversion units PDA, PDB, and PDC (first photoelectric conversion unit, second photoelectric conversion unit, and third photoelectric conversion unit) are, for example, photodiodes. The anodes of the photoelectric conversion units PDA, PDB, and PDC are connected to a ground node. The cathode of the photoelectric conversion unit PDA is connected to the source of the element connection transistor M5, the source of the element connection transistor M6, and the source of the transfer transistor M1A. The cathode of the photoelectric conversion unit PDB is connected to the drain of the element connection transistor M5 and the source of the transfer transistor M1B. The cathode of the photoelectric conversion unit PDC is connected to the drain of the element connection transistor M6 and the source of the transfer transistor M1C.

The drains of the transfer transistors M1A, M1B, and M1C are connected to the source of the reset transistor M2 and the gate of the amplification transistor M3. A node to which the drains of the transfer transistors M1A, M1B, and M1C, the source of the reset transistor M2, and the gate of the amplification transistor M3 are connected is the floating diffusion portion FD. The floating diffusion portion FD includes a capacitive component (floating diffusion capacitance) and functions as a charge holding portion. The floating diffusion capacitance includes the parasitic capacitance of the electrical path from the transfer transistors M1A, M1B, and M1C to the amplification transistor M3 via the floating diffusion portion FD.

The drain of the reset transistor M2 and the drain of the amplification transistor M3 are connected to a power supply voltage node to which voltage VDD is supplied. The source of the amplification transistor M3 is connected to the drain of the selection transistor M4. The source of the selection transistor M4 is connected to the output line 12.

A current source 13 is connected to the output line 12 . The current source 13 may be a current source whose current value can be switched, or may be a constant current source whose current value is constant.

In the case of the pixel configuration of FIG. 2, the control line 11 in each row includes signal lines connected to the gates of transfer transistors M1A, M1B, M1C, reset transistor M2, selection transistor M4, and element connection transistors M5 and M6, respectively. Control signals pTXA, pTXB, and pTXC are supplied from the vertical scanning circuit 2 to the gates of the transfer transistors M1A, M1B, and M1C, respectively. A control signal pRES is supplied from the vertical scanning circuit 2 to the gate of the reset transistor M2. A control signal pSEL is supplied from the vertical scanning circuit 2 to the gate of the selection transistor M4. Control signals pPG1 and pPG2 are supplied from the vertical scanning circuit 2 to the gates of the element connection transistors M5 and M6, respectively. The plurality of pixels 10 in the same row are connected to a common signal line and are controlled simultaneously by a common control signal.

In this embodiment, each transistor constituting the pixel 10 is an N-type MOS transistor. Therefore, when a high level control signal is supplied from the vertical scanning circuit 2, the corresponding transistor is turned on. Further, when a low level control signal is supplied from the vertical scanning circuit 2, the corresponding transistor is turned off. Further, the names of the source and drain of a MOS transistor may differ depending on the conductivity type of the transistor or the function of interest. Some or all of the names of the source and drain used in this embodiment may be called by reverse names.

Each of the photoelectric conversion units PDA, PDB, and PDC converts incident light into an amount of charge corresponding to the amount of light (photoelectric conversion). When the transfer transistor M1A turns on, it transfers the charge held by the photoelectric conversion unit PDA to the floating diffusion unit FD. When the transfer transistor M1B is turned on, the transfer transistor M1B transfers the charge held by the photoelectric conversion unit PDB to the floating diffusion unit FD. The transfer transistor M1C, when turned on, transfers the charge held by the photoelectric conversion section PDC to the floating diffusion section FD. Charges transferred from the photoelectric conversion units PDA, PDB, and PDC are held in the capacitance (floating diffusion capacitance) of the floating diffusion unit FD. As a result, the floating diffusion portion FD has a potential corresponding to the amount of charge transferred from the photoelectric conversion portions PDA, PDB, and PDC through charge-voltage conversion by the floating diffusion capacitance.

When turned on, the element connection transistor M5 controls the potential of the semiconductor region between the photoelectric conversion unit PDA and the photoelectric conversion unit PDB to a state where the charges accumulated therein can be moved. By turning on, the element connection transistor M6 controls the potential of the semiconductor region between the photoelectric conversion unit PDA and the photoelectric conversion unit PDC to a state where the charges accumulated therein can be moved. In this way, the element connection transistors M5 and M6 have a function of adding charges accumulated in a plurality of photoelectric conversion sections. Therefore, when the element connection transistor M5 or the element connection transistor M6 is on, each transfer transistor can also transfer charges transferred from a photoelectric conversion unit other than the corresponding photoelectric conversion unit.

The selection transistor M4 connects the amplification transistor M3 to the output line 12 by turning on. The amplification transistor M3 has a drain supplied with the voltage VDD and a source supplied with a bias current from the current source 13 via the selection transistor M4, and is an amplification section (source follower circuit) whose gate is an input node. Configure. As a result, the amplification transistor M3 outputs a signal based on the potential of the floating diffusion portion FD to the output line 12 via the selection transistor M4. In this sense, the amplification transistor M3 and the selection transistor M4 are output sections that output pixel signals according to the amount of charge held in the floating diffusion portion FD.

The reset transistor M2 has a function of resetting the floating diffusion portion FD by controlling the supply of voltage (voltage VDD) to the floating diffusion portion FD. The reset transistor M2 is turned on to reset the floating diffusion portion FD to a voltage corresponding to the voltage VDD.

Note that although FIG. 2 shows a configuration in which a signal is output to the corresponding output line 12 via one selection transistor M4, the configuration of the selection transistor M4 and the output line 12 is not limited to this. For example, in a configuration in which a plurality of selection transistors M4 and a plurality of output lines 12 are arranged for one pixel 10, it is possible to select the output line 12 that outputs a signal by individually controlling the plurality of selection transistors M4. A configuration may also be adopted.

FIG. 3 is a schematic plan view of the pixel 10 according to this embodiment. FIG. 3 schematically shows the arrangement of photoelectric conversion sections PDA, PDB, PDC, floating diffusion section FD, semiconductor regions and gate electrodes constituting a transistor, and the arrangement of on-chip lens 112 in a plan view of the substrate. ing. FIG. 4 is a schematic cross-sectional view of the pixel 10 according to this embodiment. FIG. 4 schematically shows a cross section taken along line AA in FIG. 3. The structure of the pixel of this embodiment will be described with mutual reference to FIGS. 3 and 4.

FIG. 3 shows semiconductor regions 101, 102, 103, 109, 110, and 111, potential control electrodes 104, 105, and transfer electrodes 106, 107, and 108 that constitute the pixel 10. Semiconductor regions 101, 102, and 103 are impurity diffusion regions that constitute photoelectric conversion units PDA, PDB, and PDC, respectively. The semiconductor regions 109, 110, and 111 are impurity diffusion regions that constitute the floating diffusion portion FD. The semiconductor region 101 has a rectangular shape, and the semiconductor regions 102 and 103 are arranged along two opposing sides of the four sides of the semiconductor region 101.

The potential control electrode 104 (first control electrode) is an electrode that controls the potential between the photoelectric conversion unit PDA and the photoelectric conversion unit PDB. Potential control electrode 104 is arranged between semiconductor region 101 and semiconductor region 102 . The potential control electrode 105 (second control electrode) is an electrode that controls the potential between the photoelectric conversion unit PDA and the photoelectric conversion unit PDC. Potential control electrode 105 is arranged between semiconductor region 101 and semiconductor region 103. That is, potential control electrodes 104 and 105 function as gates of element connection transistors M5 and M6, respectively.

The transfer electrodes 106, 107, and 108 (first transfer electrode, second transfer electrode, and third transfer electrode) are electrodes for transferring charges from the photoelectric conversion units PDA, PDB, and PDC to the floating diffusion unit FD, respectively. . Transfer electrodes 106, 107, and 108 are arranged between semiconductor regions 101, 102, and 103 and semiconductor regions 110, 109, and 111, respectively. That is, transfer electrodes 106, 107, and 108 function as gates of transfer transistors M1A, M1B, and M1C, respectively.

As shown in FIG. 4, an oxide film 121 and a wiring layer 122 are arranged in this order on one surface (first surface) of the semiconductor substrate 120 on which the photoelectric conversion units PDA, PDB, and PDC are arranged. There is. Further, on the surface (second surface) opposite to the first surface of the semiconductor substrate 120, a planarization layer 123, a color filter layer 124, and an on-chip lens 112 (first lens) are arranged in this order. In this way, the photoelectric conversion device of this embodiment has a structure in which incident light is irradiated from the second surface side opposite to the first surface side where the wiring layer 122 is arranged, so-called backside illumination. It is a type CMOS image sensor. The on-chip lens 112 is arranged to cover at least the photoelectric conversion unit PDA, and guides incident light to at least the photoelectric conversion unit PDA.

The wiring layer 122 includes a plurality of wirings 113 embedded in the interlayer insulating film 114. The plurality of wirings 113 are arranged over a plurality of layers. The plurality of wiring lines 113 are used for reading signals from the photoelectric conversion units PDA, PDB, and PDC, transmitting control signals, and the like.

The surface of the wiring layer 122 opposite to the oxide film 121 may be supported by a substrate support material (not shown). For example, a signal processing circuit such as an AD conversion circuit may be disposed on the substrate supporting material side, and processing speed can be increased. Such a photoelectric conversion device is sometimes called a stacked CMOS image sensor.

In the wiring layer 122, transfer electrodes 106, 107, and 108 are arranged at positions corresponding to the semiconductor regions 101, 102, and 103, respectively, with an oxide film 121 interposed therebetween. The oxide film 121 is an oxide having insulating properties. The oxide film 121 functions as a gate insulating film of the MOS transistor by insulating the first surface side of the semiconductor substrate 120. By applying control signals pTXA, pTXB, and pTXC of predetermined voltages to the transfer electrodes 106, 107, and 108, the charges accumulated in the photoelectric conversion units PDA, PDB, and PDC are transferred to the floating diffusion unit FD, respectively. .

Semiconductor regions 115, 116, 117, and 118 are further arranged on the semiconductor substrate 120. The semiconductor region 115 separates the photoelectric conversion unit PDA and the photoelectric conversion unit PDB. The semiconductor region 116 separates the photoelectric conversion unit PDA and the photoelectric conversion unit PDC. Semiconductor regions 117, 118 provide separation between pixel 10 shown in FIG. 4 and other elements (eg, pixels adjacent to pixel 10 shown in FIG. 4).

Potential control electrodes 104 and 105 are disposed in wiring layer 122 at positions corresponding to semiconductor regions 115 and 116, respectively, with oxide film 121 interposed therebetween. By applying a control signal pPG1 of a predetermined voltage to the potential control electrode 104, the potential of the semiconductor region between the photoelectric conversion unit PDA and the photoelectric conversion unit PDB is reduced. Thereby, the electric charges accumulated in the photoelectric conversion units PDA and PDB are controlled to be able to mutually move. Further, by applying a control signal pPG2 of a predetermined voltage to the potential control electrode 105, the potential of the semiconductor region between the photoelectric conversion unit PDA and the photoelectric conversion unit PDC is reduced. Thereby, the electric charges accumulated in the photoelectric conversion units PDA and PDC are controlled to be able to mutually move.

FIG. 5 is a diagram schematically showing the potential within a pixel according to this embodiment. FIG. 5 schematically shows the potential along the line BB in FIG. The horizontal axis in FIG. 5 indicates the position on the line BB in FIG. 3, and the vertical axis in FIG. 5 indicates the potential. The solid line in FIG. 5 shows the potential in a state where control signals pPG1 and pPG2 of a predetermined voltage are not applied to the potential control electrodes 104 and 105 (that is, when the element connection transistors M5 and M6 are off). The broken line in FIG. 5 indicates the potential in a state where control signals pPG1 and pPG2 of predetermined voltages are applied to potential control electrodes 104 and 105 (that is, when element connection transistors M5 and M6 are on). As understood from the broken lines in FIG. 5, by applying control signals pPG1 and pPG2 of predetermined voltages to potential control electrodes 104 and 105, the potentials of semiconductor regions 115 and 116 are reduced. This allows charges to move between the photoelectric conversion units PDA, PDB, and PDC.

In this embodiment, the sensitivity of the photoelectric conversion unit PDB formed by the semiconductor region 102 is lower than the sensitivity of the photoelectric conversion unit PDA formed by the semiconductor region 101. Furthermore, the sensitivity of the photoelectric conversion unit PDC formed by the semiconductor region 103 is lower than the sensitivity of the photoelectric conversion unit PDA formed by the semiconductor region 101. In this way, by providing two or more photoelectric conversion sections with different sensitivities and varying the signal output method depending on the illuminance, it is possible to expand the dynamic range. For example, at low illuminance, sensitivity can be improved by reading out a signal based on the charges accumulated in the photoelectric conversion unit PDA. Furthermore, by reading out a signal based on the charge accumulated in the photoelectric conversion unit PDB or photoelectric conversion unit PDC, which has relatively low sensitivity at high illuminance, the signal becomes less likely to be saturated. This achieves both improved sensitivity during low illuminance and suppression of signal saturation during high illuminance, expanding the dynamic range.

Furthermore, in this embodiment, control signals pPG1 and pPG2 of predetermined voltages are applied to the potential control electrodes 104 and 105 at low illuminance to create a state in which charges can move between the photoelectric conversion units PDA, PDB, and PDC. control is performed. As a result, the charges generated by the photoelectric conversion units PDA, PDB, and PDC are added at low illuminance. In this case, the light receiving area is substantially expanded from the area of the photoelectric conversion unit PDA to the combined area of the photoelectric conversion units PDA, PDB, and PDC. This increases the SNR (Signal-to-Noise Ratio) at low illuminance.

FIG. 6 is a graph schematically showing the relationship between illuminance and SNR according to this embodiment. The horizontal axis in FIG. 6 represents the illuminance of light incident on the pixel 10, and the vertical axis in FIG. 6 represents the SNR. Note that the illuminance E3 in FIG. 6 indicates a threshold value at which the operation at low illuminance and the operation at high illuminance are switched. That is, when the illuminance of the incident light to the photoelectric conversion device is lower than E3, the above-mentioned readout operation at low illuminance is performed, and when the illuminance of the incident light to the photoelectric conversion device is E3 or higher, the above-mentioned read operation is performed. A read operation is performed during high illuminance. As a result, at illuminance E3, a difference in SNR value occurs due to switching of operations.

The solid line in FIG. 6 indicates the SNR in a state where control signals pPG1 and pPG2 of predetermined voltages are not applied to the potential control electrodes 104 and 105 (that is, a state in which the element connection transistors M5 and M6 are off). In other words, the solid line in FIG. 6 can also be understood as a comparative example without the potential control electrodes 104 and 105. Illuminance E2 in FIG. 6 indicates the lowest illuminance at which signal acquisition is possible in this state.

The broken line in FIG. 6 indicates the SNR in a state where control signals pPG1 and pPG2 of predetermined voltages are applied to potential control electrodes 104 and 105 (that is, when element connection transistors M5 and M6 are on). Illuminance E1 in FIG. 6 indicates the lowest illuminance at which signal acquisition is possible in this state.

As can be understood by comparing the solid line and the broken line in the vicinity of illuminance E1 and illuminance E2 in FIG. Since the charges added are added, the minimum illuminance becomes lower. Therefore, signal acquisition is possible even at lower illuminance, and the dynamic range is further expanded.

As described above, according to this embodiment, the dynamic range can be further expanded by arranging the potential control electrodes 104 and 105 and creating a state in which charges can move between the photoelectric conversion units PDA, PDB, and PDC. A photoelectric conversion device is provided.

In addition, by creating a state in which charges can move between the photoelectric conversion units PDA, PDB, and PDC, even if light that saturates the highly sensitive photoelectric conversion unit PDA is incident, the charges will be transferred to other photoelectric conversion units. You can move to the department. That is, the saturated charge amount substantially increases from the value of the photoelectric conversion unit PDA to the value of the photoelectric conversion units PDA, PDB, and PDC combined. As a result, the influence of saturation can be reduced and the range of illuminance in which high-sensitivity readout is possible can be expanded.

In addition, in the above explanation, an example is shown in which one high-sensitivity photoelectric conversion unit PDA and two low-sensitivity photoelectric conversion units PDB and PDC are arranged, but the number of these photoelectric conversion units is It is not particularly limited. That is, any pixel configuration that includes one or more high-sensitivity photoelectric conversion units and one or more low-sensitivity photoelectric conversion units may be used.

The structure that provides a sensitivity difference that makes the sensitivity of the photoelectric conversion units PDB and PDC lower than that of the photoelectric conversion unit PDA is not particularly limited. As an example of a structure that provides a sensitivity difference, as shown in FIGS. 2 and 3, in plan view, the area of the light receiving surface of the photoelectric conversion unit PDA is equal to the area of the light receiving surface of the photoelectric conversion unit PDB or the photoelectric conversion unit PDC. One example is to make it larger than the area. As a result, more light is incident on the photoelectric conversion unit PDA than on the photoelectric conversion unit PDB or the photoelectric conversion unit PDC, so the sensitivity of the photoelectric conversion unit PDA is higher than the sensitivity of the photoelectric conversion unit PDB or photoelectric conversion unit PDC. It can be expensive.

In addition, as another structure, as shown in FIGS. 2 and 3, the photoelectric conversion unit PDA is arranged near the center of the on-chip lens 112, particularly on the optical axis of the on-chip lens 112, and the photoelectric conversion unit PDA is arranged outside the on-chip lens 112. An example of such a structure is that a photoelectric conversion unit PDB or a photoelectric conversion unit PDC is disposed in the photoelectric conversion unit PDB or PDC. Since the on-chip lens 112 concentrates more light on the photoelectric conversion unit PDA, the sensitivity of the photoelectric conversion unit PDA can be higher than the sensitivity of the photoelectric conversion unit PDB or the photoelectric conversion unit PDC.

Furthermore, in charge transfer during low illuminance, it is more desirable to use only the transfer transistor M1A (transfer electrode 106) than to use the transfer transistors M1A, M1B, and M1C (transfer electrodes 106, 107, and 108). This reduces noise caused by transfer.

Further, the impurity concentration of the semiconductor region 101 is preferably higher than the impurity concentration of the semiconductor region 102 or the semiconductor region 103. This realizes a potential structure in which charges generated in the photoelectric conversion unit PDB or the photoelectric conversion unit PDC can easily move to the photoelectric conversion unit PDA. Therefore, charges generated in the photoelectric conversion unit PDB or the photoelectric conversion unit PDC are less likely to remain in the photoelectric conversion unit PDB or the photoelectric conversion unit PDC during transfer, and accuracy is further improved.

[Second embodiment]
In this embodiment, a modification of the planar structure of the pixel 10 of the first embodiment will be described. Description of parts common to the first embodiment will be omitted.

FIG. 7 is a schematic plan view of the pixel 10 according to this embodiment. As shown in FIG. 7, a semiconductor region 101 constituting the photoelectric conversion unit PDA is arranged on the optical axis of the on-chip lens 112. The semiconductor region 101 has a rectangular shape. Further, outside the semiconductor region 101, that is, outside the optical axis of the on-chip lens 112, a semiconductor region 102 forming the photoelectric conversion unit PDB and a semiconductor region 103 forming the photoelectric conversion unit PDC are arranged. The semiconductor region 102 is arranged along two adjacent sides of the four sides of the outer periphery of the semiconductor region 101, and the semiconductor region 103 is arranged along the other two sides of the semiconductor region 101. That is, the semiconductor region 102 and the semiconductor region 103 are arranged so as to surround the semiconductor region 101. By arranging the semiconductor regions 101, 102, and 103 in this manner, the light focusing range of the on-chip lens 112 can be efficiently utilized.

Also in this embodiment, similarly to the first embodiment, a photoelectric conversion device capable of expanding the dynamic range is provided. Further, by arranging the on-chip lens 112 and the semiconductor regions 101, 102, and 103 as described above, more of the light collected by the on-chip lens 112 is concentrated on the photoelectric conversion unit PDA. Thereby, the difference between the sensitivity of the photoelectric conversion unit PDA and the sensitivity of the photoelectric conversion unit PDB or the photoelectric conversion unit PDC can be made larger.

Note that the planar shape of the semiconductor region 101 is not limited to a square. It is desirable that the planar shape of the semiconductor region 101 is such that the surrounding semiconductor regions 102 and 103 can be efficiently arranged. For example, the planar shape of the semiconductor region 101 is preferably a polygon having four or more sides, and the planar shape of the semiconductor regions 102 and 103 is preferably a shape along two or more sides of the semiconductor region 101.

[Third embodiment]
In this embodiment, a modification of the cross-sectional structure of the pixel 10 of the first embodiment will be described. Description of parts common to the first embodiment will be omitted.

FIG. 8 is a schematic cross-sectional view of the pixel 10 according to this embodiment. As shown in FIG. 8, in the incident direction of light, the semiconductor region 101 constituting the photoelectric conversion unit PDA is closer to the semiconductor region 102 constituting the photoelectric conversion unit PDB or the semiconductor region 103 constituting the photoelectric conversion unit PDC. It's also long. In other words, the depth of the semiconductor region 101 when viewed from the first surface is deeper than the depth of the semiconductor region 102 or 103 when viewed from the first surface. Therefore, the efficiency of photoelectric conversion in the photoelectric conversion unit PDA is higher than the efficiency of photoelectric conversion in the photoelectric conversion unit PDB or the photoelectric conversion unit PDC. Thereby, the difference between the sensitivity of the photoelectric conversion unit PDA and the sensitivity of the photoelectric conversion unit PDB or the photoelectric conversion unit PDC can be made larger.

Also in this embodiment, similarly to the first embodiment, a photoelectric conversion device capable of expanding the dynamic range is provided. Furthermore, by making the photoelectric conversion section PDA thicker than the photoelectric conversion section PDB or the photoelectric conversion section PDC as described above, the difference between the sensitivity of the photoelectric conversion section PDA and the sensitivity of the photoelectric conversion section PDB or photoelectric conversion section PDC can be reduced. Can be made larger.

Furthermore, as shown in FIG. 8, the semiconductor regions 117 and 118 (first isolation regions) are longer than the semiconductor regions 115 and 116 (second isolation regions) in the direction of light incidence. In other words, the depth of the semiconductor regions 117 and 118 when viewed from the first surface is deeper than the depth of the semiconductor regions 115 and 116 when viewed from the first surface. In other words, the element isolation part between the pixel 10 and another element (for example, the pixel adjacent to the pixel 10 shown in FIG. 8) is arranged to a deeper position than the element isolation part between the photoelectric conversion parts. There is. This reduces charge leakage from the pixel 10 to other elements. According to this configuration, the sensitivity when adding the charges of the photoelectric conversion units PDA, PDB, and PDC can be improved.

[Fourth embodiment]
In this embodiment, a modification of the structure of the on-chip lens of the pixel 10 of the first embodiment will be described. Description of parts common to the first embodiment will be omitted.

FIG. 9 is a schematic plan view of the pixel 10 according to this embodiment. FIG. 10 is a schematic cross-sectional view of the pixel 10 according to this embodiment. FIG. 10 schematically shows a cross section taken along line CC in FIG. The structure of the pixel 10 of this embodiment will be described with mutual reference to FIGS. 9 and 10.

As shown in FIGS. 9 and 10, in the pixel 10 of this embodiment, on-chip lenses 125, 126, and 127 are arranged in place of the on-chip lens 112 of FIGS. 3 and 4. On-chip lenses 125, 126, and 127 are arranged corresponding to photoelectric conversion units PDA, PDB, and PDC, respectively. In the light incident direction, the on-chip lens 125 (first lens) is arranged to cover the photoelectric conversion unit PDA. In the light incident direction, the on-chip lens 126 (second lens) is arranged to cover at least a portion of the photoelectric conversion unit PDB. In the light incident direction, the on-chip lens 127 is arranged to cover at least a portion of the photoelectric conversion unit PDC. The on-chip lens 125 mainly guides incident light to the photoelectric conversion unit PDA. The on-chip lens 126 mainly guides incident light to the photoelectric conversion unit PDB. The on-chip lens 127 mainly guides incident light to the photoelectric conversion unit PDC.

In this embodiment, a plurality of on-chip lenses 125, 126, and 127 are arranged corresponding to the plurality of photoelectric conversion units PDA, PDB, and PDC, respectively. Thereby, the on-chip lens 125 can efficiently concentrate incident light on the photoelectric conversion unit PDA. Further, the area of each of the on-chip lenses 126 and 127 in a plan view is smaller than the area of the on-chip lens 125 in a plan view. As a result, the amount of light that enters the photoelectric conversion units PDB and PDC via the on-chip lenses 126 and 127 is smaller than the amount of light that enters the photoelectric conversion unit PDA. Such a relationship in the amount of incident light can be realized by appropriately adjusting the area and position of each on-chip lens. Furthermore, the height of the on-chip lens 125 and the heights of the on-chip lenses 126 and 127 may be different from each other. Note that in FIG. 9, each of the on-chip lenses 125, 126, and 127 is depicted as an elliptical on-chip lens, but the shape of the lens is not limited to this. The on-chip lenses 125, 126, and 127 may have, for example, a perfect circular shape, or each on-chip lens may have a different shape, depending on the shape of the photoelectric conversion units PDA, PDB, and PDC.

Also in this embodiment, similarly to the first embodiment, a photoelectric conversion device capable of expanding the dynamic range is provided. Furthermore, since the plurality of on-chip lenses 125, 126, 127 are arranged corresponding to the plurality of photoelectric conversion units PDA, PDB, PDC, the area and height of the plurality of on-chip lenses 125, 126, 127 can be reduced. The design, position, etc. can be adjusted individually. Therefore, the amount of light incident on each of the photoelectric conversion units PDA, PDB, and PDC can be effectively adjusted, and design adjustment for expanding the dynamic range can be performed more suitably.

[Fifth embodiment]
The photoelectric conversion device in the embodiment described above is applicable to various devices. Examples of devices include digital still cameras, digital camcorders, camera heads, copying machines, fax machines, mobile phones, vehicle-mounted cameras, observation satellites, surveillance cameras, and the like. FIG. 11 shows a block diagram of a digital still camera as an example of the device.

The device 70 shown in FIG. 11 includes a barrier 706, a lens 702, an aperture 704, and an imaging device 700 (an example of a photoelectric conversion device). In addition, the device 70 further includes a signal processing section (processing device) 708, a timing generation section 720, an overall control/calculation section 718 (control device), a memory section 710 (storage device), a recording medium control I/F section 716, It includes a recording medium 714 and an external I/F section 712. At least one of the barrier 706, the lens 702, and the aperture 704 is an optical device corresponding to the device. Barrier 706 protects lens 702 , and lens 702 forms an optical image of a subject onto imaging device 700 . An aperture 704 makes the amount of light passing through the lens 702 variable. The imaging device 700 is configured as in the embodiment described above, and converts the optical image formed by the lens 702 into image data (image signal). The signal processing unit 708 performs various corrections, data compression, etc. on the imaging data output from the imaging device 700. The timing generating section 720 outputs various timing signals to the imaging device 700 and the signal processing section 708. An overall control/calculation section 718 controls the entire digital still camera, and a memory section 710 temporarily stores image data. The recording medium control I/F unit 716 is an interface for recording or reading image data on the recording medium 714, and the recording medium 714 is a removable recording medium such as a semiconductor memory for recording or reading image data. It is. External I/F section 712 is an interface for communicating with an external computer or the like. Timing signals and the like may be input from outside the device. Further, the device 70 may further include a display device (monitor, electronic viewfinder, etc.) that displays information obtained by the photoelectric conversion device. The device includes at least a photoelectric conversion device. Furthermore, the device 70 includes at least one of an optical device, a control device, a processing device, a display device, a storage device, and a mechanical device that operates based on information obtained by the photoelectric conversion device. The mechanical device is a movable part (for example, a robot arm) that operates in response to a signal from a photoelectric conversion device.

Each pixel may include a plurality of photoelectric conversion units (a first photoelectric conversion unit and a second photoelectric conversion unit). The signal processing unit 708 processes a pixel signal based on the charge generated in the first photoelectric conversion unit and a pixel signal based on the charge generated in the second photoelectric conversion unit, and obtains distance information from the imaging device 700 to the subject. may be configured to obtain.

[Sixth embodiment]
FIGS. 12(a) and 12(b) are block diagrams of equipment related to the in-vehicle camera in this embodiment. The device 80 includes the imaging device 800 (an example of a photoelectric conversion device) of the embodiment described above, and a signal processing device (processing device) that processes a signal from the imaging device 800. The device 80 includes an image processing unit 801 that performs image processing on a plurality of image data acquired by the imaging device 800, and a device 80 that calculates parallax (phase difference of parallax images) from the plurality of image data acquired by the device 80. It has a parallax calculation unit 802 that performs the calculation. The device 80 also includes a distance measurement unit 803 that calculates the distance to the object based on the calculated parallax, and a collision determination unit 804 that determines whether there is a possibility of a collision based on the calculated distance. has. Here, the parallax calculation unit 802 and the distance measurement unit 803 are an example of distance information acquisition means that acquires distance information to the target object. That is, distance information is information regarding parallax, defocus amount, distance to a target object, and the like. The collision determination unit 804 may determine the possibility of collision using any of these distance information. The distance information acquisition means may be realized by specially designed hardware or may be realized by a software module. Further, it may be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination thereof.

The device 80 is connected to a vehicle information acquisition device 810, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. Further, a control ECU 820 is connected to the device 80, which is a control device that outputs a control signal for generating a braking force on the vehicle based on the determination result of the collision determination unit 804. The device 80 is also connected to a warning device 830 that issues a warning to the driver based on the determination result of the collision determination unit 804. For example, if the collision determination unit 804 determines that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid the collision and reduce damage by applying the brakes, releasing the accelerator, or suppressing engine output. The alarm device 830 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or applying vibration to the seat belt or steering wheel. The device 80 functions as a control means for controlling the operation of controlling the vehicle as described above.

In this embodiment, the device 80 images the surroundings of the vehicle, for example, the front or rear. FIG. 12(b) shows equipment for imaging the front of the vehicle (imaging range 850). A vehicle information acquisition device 810 serving as an imaging control means sends an instruction to the device 80 or the imaging device 800 to perform an imaging operation. With such a configuration, the accuracy of distance measurement can be further improved.

In the above, an example of control to avoid collision with other vehicles has been described, but it can also be applied to control to automatically drive while following other vehicles, control to automatically drive to avoid running out of the lane, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving objects (mobile devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied not only to mobile objects but also to a wide range of devices that utilize object recognition or biometric recognition, such as intelligent transportation systems (ITS) and monitoring systems.

[Modified embodiment]
The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, an example in which a part of the configuration of one embodiment is added to another embodiment, or an example in which a part of the configuration in another embodiment is replaced is also an embodiment of the present invention.

The disclosure herein includes the complement of the concepts described herein. In other words, if the specification includes, for example, the statement "A is B" (A=B), even if the statement "A is not B" (A≠B) is omitted, the specification does not apply. shall be deemed to disclose or suggest that "A is not B." This is because when it is stated that "A is B", it is assumed that the case "A is not B" is being considered.

The disclosure content of this specification includes the following configurations.
(Configuration 1)
a first photoelectric conversion section;
a second photoelectric conversion section having lower sensitivity than the first photoelectric conversion section;
a floating diffusion section to which charges generated in the first photoelectric conversion section and the second photoelectric conversion section are transferred;
a first transfer electrode that transfers charge from the first photoelectric conversion section to the floating diffusion section;
a second transfer electrode that transfers charge from the second photoelectric conversion section to the floating diffusion section;
a first control electrode that controls the potential between the first photoelectric conversion section and the second photoelectric conversion section so that charges can move between the first photoelectric conversion section and the second photoelectric conversion section; ,
A photoelectric conversion device characterized by having the following.
(Configuration 2)
The photoelectric conversion device according to configuration 1, further comprising a first lens arranged to cover the first photoelectric conversion section and guiding incident light to the first photoelectric conversion section.
(Configuration 3)
The photoelectric conversion according to configuration 2, wherein the first lens is arranged so as to further cover the second photoelectric conversion section, and guides incident light to the first photoelectric conversion section and the second photoelectric conversion section. Device.
(Configuration 4)
The photoelectric conversion device according to configuration 3, wherein the amount of light guided to the first photoelectric conversion section is greater than the amount of light guided to the second photoelectric conversion section.
(Configuration 5)
The first photoelectric conversion section is arranged on the optical axis of the first lens,
The photoelectric conversion device according to configuration 3 or 4, wherein the second photoelectric conversion section is not arranged on the optical axis of the first lens.
(Configuration 6)
a first lens arranged to cover the first photoelectric conversion section and guide incident light to the first photoelectric conversion section;
a second lens arranged to cover at least a portion of the second photoelectric conversion section and guiding incident light to the second photoelectric conversion section;
The photoelectric conversion device according to Configuration 1, further comprising:
(Configuration 7)
The photoelectric conversion device according to configuration 6, wherein the amount of light guided to the first photoelectric conversion section is greater than the amount of light guided to the second photoelectric conversion section.
(Configuration 8)
8. The photoelectric conversion device according to any one of configurations 1 to 7, wherein the area of the light receiving surface of the first photoelectric conversion section is larger than the area of the light receiving surface of the second photoelectric conversion section.
(Configuration 9)
According to any one of configurations 1 to 8, the impurity concentration of the semiconductor region constituting the first photoelectric conversion section is higher than the impurity concentration of the semiconductor region constituting the second photoelectric conversion section. Photoelectric conversion device.
(Configuration 10)
According to any one of configurations 1 to 9, the semiconductor region constituting the first photoelectric conversion section is longer than the semiconductor region constituting the second photoelectric conversion section in the direction of incidence of light. Photoelectric conversion device.
(Configuration 11)
a first element isolation region that isolates a region including the first photoelectric conversion unit and the second photoelectric conversion unit from other elements;
a second element isolation region that isolates between the first photoelectric conversion section and the second photoelectric conversion section;
It further has
The photoelectric conversion device according to any one of Structures 1 to 10, wherein the first element isolation region is longer than the second element isolation region in the direction of incidence of light.
(Configuration 12)
In plan view, the outer periphery of the first photoelectric conversion section has four or more sides, and the second photoelectric conversion section is arranged along two or more sides of the outer periphery of the first photoelectric conversion section. The photoelectric conversion device according to any one of Features 1 to 11.
(Configuration 13)
In a state where charges can move between the first photoelectric conversion section and the second photoelectric conversion section, the transfer of charges from the first photoelectric conversion section and the second photoelectric conversion section to the floating diffusion section includes: The photoelectric conversion device according to any one of Configurations 1 to 12, characterized in that the photoelectric conversion device is performed using only the first transfer electrode.
(Configuration 14)
a third photoelectric conversion section having lower sensitivity than the first photoelectric conversion section;
a third transfer electrode that transfers charge from the third photoelectric conversion section to the floating diffusion section;
a second control electrode that controls the potential between the first photoelectric conversion section and the third photoelectric conversion section so that charges can move between the first photoelectric conversion section and the third photoelectric conversion section; ,
The photoelectric conversion device according to any one of Structures 1 to 13, further comprising:
(Configuration 15)
15. The photoelectric conversion device according to configuration 14, wherein the second photoelectric conversion section and the third photoelectric conversion section are arranged so as to surround the first photoelectric conversion section in a plan view.
(Configuration 16)
Configurations 1 to 15 characterized in that the potential is controlled so that charges can move between the first photoelectric conversion unit and the second photoelectric conversion unit when illuminance is lower than a predetermined threshold. The photoelectric conversion device according to any one of the above.
(Configuration 17)
The photoelectric conversion device according to any one of Configurations 1 to 16,
an optical device compatible with the photoelectric conversion device;
a control device that controls the photoelectric conversion device;
a processing device that processes the signal output from the photoelectric conversion device;
a display device that displays information obtained by the photoelectric conversion device;
at least one of a storage device that stores information obtained by the photoelectric conversion device; and a mechanical device that operates based on the information obtained by the photoelectric conversion device;
A device characterized by comprising:
(Configuration 18)
18. The device according to configuration 17, wherein the processing device processes image signals generated by a plurality of photoelectric conversion units, respectively, and acquires distance information from the photoelectric conversion device to the subject.

The present invention provides a system or device with a program that implements one or more functions of the embodiments described above via a network or a storage medium, and one or more processors in a computer of the system or device reads and executes the program. This can also be achieved by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Note that the above-described embodiments are merely examples of implementation of the present invention, and the technical scope of the present invention should not be interpreted to be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from its technical idea or main features.

101, 102, 103 Semiconductor regions 104, 105 Potential control electrodes 106, 107, 108 Transfer electrode FD Floating diffusion section PDA, PDB, PDC Photoelectric conversion section

Claims (18)

a first photoelectric conversion section;
a second photoelectric conversion section having lower sensitivity than the first photoelectric conversion section;
a floating diffusion section to which charges generated in the first photoelectric conversion section and the second photoelectric conversion section are transferred;
a first transfer electrode that transfers charge from the first photoelectric conversion section to the floating diffusion section;
a second transfer electrode that transfers charge from the second photoelectric conversion section to the floating diffusion section;
a first control electrode that controls the potential between the first photoelectric conversion section and the second photoelectric conversion section so that charges can move between the first photoelectric conversion section and the second photoelectric conversion section; ,
A photoelectric conversion device characterized by having the following. The photoelectric conversion device according to claim 1, further comprising a first lens arranged to cover the first photoelectric conversion section and guiding incident light to the first photoelectric conversion section. The photoelectric converter according to claim 2, wherein the first lens is arranged to further cover the second photoelectric converter and guides incident light to the first photoelectric converter and the second photoelectric converter. conversion device. The photoelectric conversion device according to claim 3, wherein the amount of light guided to the first photoelectric conversion section is greater than the amount of light guided to the second photoelectric conversion section. The first photoelectric conversion section is arranged on the optical axis of the first lens,
The photoelectric conversion device according to claim 3, wherein the second photoelectric conversion section is not arranged on the optical axis of the first lens. a first lens arranged to cover the first photoelectric conversion section and guide incident light to the first photoelectric conversion section;
a second lens arranged to cover at least a portion of the second photoelectric conversion section and guiding incident light to the second photoelectric conversion section;
The photoelectric conversion device according to claim 1, further comprising: The photoelectric conversion device according to claim 6, wherein the amount of light guided to the first photoelectric conversion section is greater than the amount of light guided to the second photoelectric conversion section. The photoelectric conversion device according to claim 1, wherein the area of the light receiving surface of the first photoelectric conversion section is larger than the area of the light receiving surface of the second photoelectric conversion section. The photoelectric conversion device according to claim 1, wherein an impurity concentration of a semiconductor region that constitutes the first photoelectric conversion section is higher than an impurity concentration of a semiconductor region that constitutes the second photoelectric conversion section. 2. The photoelectric conversion device according to claim 1, wherein a semiconductor region forming the first photoelectric conversion section is longer than a semiconductor region forming the second photoelectric conversion section in a light incident direction. a first element isolation region that isolates a region including the first photoelectric conversion unit and the second photoelectric conversion unit from other elements;
a second element isolation region that isolates between the first photoelectric conversion section and the second photoelectric conversion section;
It further has
The photoelectric conversion device according to claim 1, wherein the first element isolation region is longer than the second element isolation region in the direction of incidence of light. In plan view, the outer periphery of the first photoelectric conversion section has four or more sides, and the second photoelectric conversion section is arranged along two or more sides of the outer periphery of the first photoelectric conversion section. The photoelectric conversion device according to claim 1. In a state where charges can move between the first photoelectric conversion section and the second photoelectric conversion section, the transfer of charges from the first photoelectric conversion section and the second photoelectric conversion section to the floating diffusion section includes: The photoelectric conversion device according to claim 1, characterized in that the photoelectric conversion is performed only by the first transfer electrode. a third photoelectric conversion section having lower sensitivity than the first photoelectric conversion section;
a third transfer electrode that transfers charge from the third photoelectric conversion section to the floating diffusion section;
a second control electrode that controls the potential between the first photoelectric conversion section and the third photoelectric conversion section so that charges can move between the first photoelectric conversion section and the third photoelectric conversion section; ,
The photoelectric conversion device according to claim 1, further comprising: The photoelectric conversion device according to claim 14, wherein the second photoelectric conversion section and the third photoelectric conversion section are arranged so as to surround the first photoelectric conversion section in a plan view. 2. The potential is controlled such that when illuminance is lower than a predetermined threshold, charges can move between the first photoelectric conversion section and the second photoelectric conversion section. The photoelectric conversion device described. A photoelectric conversion device according to any one of claims 1 to 16,
an optical device compatible with the photoelectric conversion device;
a control device that controls the photoelectric conversion device;
a processing device that processes the signal output from the photoelectric conversion device;
a display device that displays information obtained by the photoelectric conversion device;
at least one of a storage device that stores information obtained by the photoelectric conversion device; and a mechanical device that operates based on the information obtained by the photoelectric conversion device;
A device characterized by comprising: The device according to claim 17, wherein the processing device processes image signals generated by a plurality of photoelectric conversion units, respectively, and acquires distance information from the photoelectric conversion device to the subject.

Images