Image Sensor

Abstract

An image sensor is disclosed, comprising: a first photodiode group; a second photodiode group; a first transfer transistor group; a second transfer transistor group; a floating diffusion region of a substrate in which charges generated in the first photodiode group are stored; and a power supply node for applying a power supply voltage to the second photodiode group. A barrier voltage is applied to at least one transfer transistor of the second transfer transistor group. The power supply voltage causes the charges generated in the second photodiode group to migrate to the power supply node, and the barrier voltage forms a barrier between the second photodiode group and the floating diffusion region.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2019-0160516 filed on December 5, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Technical Field

[0003] The present disclosure relates to an image sensor. Background Art

[0004] An image sensor is a semiconductor-based sensor for receiving light and generating an electrical signal. For example, an image sensor converts light into an electrical signal that conveys information for forming an image. An image sensor may include: a pixel array including a plurality of pixels; a logic circuit for driving the pixel array and generating an image, etc. The plurality of pixels may include: a photodiode for generating an electric charge by reacting to external light; a pixel circuit for converting the charge generated from the photodiode into an electrical signal, etc. Traditionally, image sensors have been used in cameras to capture still images and video images, but are now widely used in smartphones, tablet personal computers (PCs), laptop computers, televisions, vehicles, etc. Recently, various methods for improving the noise characteristics, dynamic range, etc. of image sensors have been developed. Summary of the invention

[0005] Example embodiments provide an image sensor capable of limiting and / or preventing crosstalk from occurring while providing an auto focus function.

[0006] According to example embodiments, an image sensor includes: a first photodiode group including photodiodes and a second photodiode group including photodiodes; a first transfer transistor group including at least one transfer transistor connected to the first photodiode group; a second transfer transistor group including at least one transfer transistor connected to the second photodiode group; a floating diffusion region of a substrate, the floating diffusion region being configured to store charges generated in the first photodiode group when at least one transfer transistor of the first transfer transistor group is turned on; and a power supply node connected to the second photodiode group, the power supply node being configured to have a power supply voltage applied thereto so as to apply the power supply voltage to the second photodiode group. The power supply voltage causes the charges generated in the second photodiode group to migrate to the power supply node. At least one transfer transistor of the second transfer transistor group is configured to have a barrier voltage applied thereto. The barrier voltage forms a barrier between the second photodiode group and the floating diffusion region.

[0007] According to an example embodiment, an image sensor includes: a first pixel region and a second pixel region sharing a single microlens; a device isolation layer electrically isolating the first pixel region and the second pixel region from each other; at least one transfer transistor connected to the first pixel region; and at least one drain terminal connected to the second pixel region. The at least one drain terminal is configured to have a power supply voltage applied thereto.

[0008] According to an example embodiment, an image sensor includes a normal pixel group configured to generate an image and an autofocus pixel group configured to provide an autofocus function. The autofocus pixel group and the normal pixel group have substantially the same sensitivity as each other. The autofocus pixel group includes: unit pixels that share a single microlens and each include a single photodiode; a device isolation layer that electrically isolates the unit pixels from each other; and a drain terminal configured to have a constant voltage input therein. The photodiodes in the autofocus pixel group include a first photodiode group and a second photodiode group. The drain terminal is connected to the second photodiode group. The first photodiode group is configured to generate charges that migrate from the first photodiode group to a floating diffusion region of a substrate. The second photodiode is configured to generate charges that are discharged to the drain terminal.

[0009] According to an example embodiment, an image sensor includes: a pixel array including a normal pixel group and an autofocus pixel group; and a controller configured to generate an image based on a signal generated from the normal pixel group and to provide an autofocus function based on a signal generated from the autofocus pixel group. The autofocus pixel group includes: unit pixels that share a single microlens and each include any one of an autofocus photodiode and a drain photodiode; a device isolation layer that electrically isolates the unit pixels from each other; and a drain terminal connected to the drain photodiode. The autofocus photodiode is configured to generate charges that migrate to a floating diffusion region of a substrate, and the charges generated from the drain photodiode are discharged to the drain terminal. The pixel array has any one of a red-green-green-blue (RGGB) mode and a red-green-blue-white (RGBW) mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other aspects, features and effects of the present disclosure will be more clearly understood from the following detailed description in conjunction with the accompanying drawings.

[0011] Figure 1 is a block diagram of an image sensor according to example embodiments.

[0012] Figure 2 and Figure 3 are schematic diagrams of image sensors according to example embodiments.

[0013] Figure 4 The operation of an image sensor according to example embodiments is illustrated.

[0014] Figure 5 is a schematic circuit diagram illustrating a pixel included in an image sensor according to example embodiments.

[0015] Figure 6 The operation of an image sensor according to example embodiments is illustrated.

[0016] Fig. 7A and Figure 7B A pixel array according to an example embodiment is shown.

[0017] Figure 8 is a schematic circuit diagram illustrating a pixel group according to example embodiments.

[0018] Fig. 9A is a plan view of a general pixel group according to example embodiments.

[0019] Fig. 9B and Fig. 9C are plan views of auto-focus pixel groups according to example embodiments, respectively.

[0020] FIG. 10A to FIG. 10F The operation of an auto-focus pixel group according to an example embodiment is shown.

[0021] Fig.11A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 11B is along Fig.11A The cross-sectional view taken along the line II-II' in FIG. Fig. 11C is along Fig.11A A cross-sectional view taken along line III-III'.

[0022] Fig. 12A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 12B is along Fig. 12A A cross-sectional view taken along line IV-IV'.

[0023] Fig.13A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 13B is along Fig.13A Cross-sectional view taken along line V-V'.

[0024] Fig.14A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 14B is along Fig.14A A cross-sectional view taken along line VI-VI'.

[0025] Fig.15 is a plan view of an auto-focus pixel group according to example embodiments.

[0026] Fig.16A pixel array according to an example embodiment is shown.

[0027] Fig.17 is a plan view of an auto-focus pixel group according to example embodiments.

[0028] Fig.18 is a partial cross-sectional view of a pixel according to example embodiments.

[0029] Fig.19A and Fig.19B The sensitivity of an image sensor according to example embodiments is shown.

[0030] Fig. 20 is a schematic block diagram of an electronic device including an image sensor according to example embodiments. DETAILED DESCRIPTION

[0031] When the term "about" or "substantially" is used in conjunction with a numerical value in this specification, it is intended that the associated numerical value includes a tolerance of ±10% around the numerical value. When a range is specified, the range includes all values ​​therebetween, for example, increments of 0.1%.

[0032] Hereinafter, example embodiments will be described with reference to the accompanying drawings.

[0033] Figure 1 is a block diagram of an image sensor according to example embodiments.

[0034] Reference Figure 1 , an image sensor 100 according to example embodiments may include a pixel array 110 , a row driver 120 , a readout circuit 130 , a timing controller 140 , and a signal processing circuit 150 .

[0035] The image sensor 100 may convert light received from an external device into an electrical signal and may generate image data. The pixel array 110 included in the image sensor 100 may include a plurality of pixels PX, and the plurality of pixels PX may include a photoelectric device configured to receive light and generate a charge. The photoelectric device may be, for example, a photodiode PD. The plurality of pixels PX may be connected to a plurality of row lines extending in a first direction and a plurality of column lines extending in a second direction. In an example embodiment, each pixel PX of the plurality of pixels PX may include two or more photoelectric devices to generate pixel signals corresponding to light of various colors or to provide an autofocus function.

[0036] Each pixel PX of the plurality of pixels PX may include a pixel circuit configured to generate a pixel signal from a charge generated from a photodiode. As an example, the pixel circuit may include a transfer transistor, a drive transistor, a select transistor, a reset transistor, a floating diffusion region, etc. The pixel circuit may output a reset voltage and a pixel voltage. The pixel voltage may correspond to a charge generated from a photodiode included in each of the plurality of pixels and stored in a floating diffusion region. In an example embodiment, two or more adjacent pixels PX may constitute a single pixel group, and the two or more pixels PX included in the pixel group may share at least a portion of a transfer transistor, a drive transistor, a select transistor, and a reset transistor.

[0037] The row driver 120 may input a driving signal to a plurality of row lines to drive the pixel array 110. For example, the driving signal may include a transfer control signal TS configured to control a transfer transistor of a pixel circuit, a reset control signal RS configured to control a reset transistor of the pixel circuit, and a selection control signal SEL configured to control a selection transistor of the pixel circuit, etc. As an example, the row driver 120 may sequentially drive a plurality of row drivers.

[0038] The readout circuit 130 may include a ramp signal generator 131, a sampling circuit 132, an analog-to-digital converter (ADC) 133, and a buffer 134. The sampling circuit may include a plurality of samplers connected to the pixel PX through a plurality of column lines. In an example embodiment, the sampler may be a correlated double sampler (CDS). The sampler may detect a reset voltage and a pixel voltage from a pixel PX connected to a selected row line driven by the row driver 120 from among a plurality of row lines. The sampler may output the difference between the reset voltage and the pixel voltage as an analog signal.

[0039] The analog-to-digital converter 133 can receive the ramp voltage V from the ramp signal generator 131. RMP The analog signal can be received from the sampling circuit 132. The analog-to-digital converter 133 can convert the analog signal into a ramp voltage V RMP The comparison is performed, and the comparison result can be converted into a digital signal and the digital signal can be output as the image data LSB. The image data LSB can have a value that increases as the difference between the reset voltage and the pixel voltage increases. Therefore, the image data LSB can have a value that increases as the intensity of light received by the photodiode increases.

[0040] The buffer 134 may temporarily store the LSB of the image data received from the analog-to-digital converter 133 .

[0041] The row driver 120 and the readout circuit 130 may be controlled by a timing controller 140. The timing controller 140 may control operation timings of the row driver 120 and the readout circuit 130. Under the control of the timing controller 140, the row driver 120 may control the operation of the pixel array 110 in units of rows.

[0042] The signal processing circuit 150 may generate an image using the image data LSB transmitted from the buffer 134. The signal processing circuit 150 may process the image data LSB and may output the processed image data as an image.

[0043] In some embodiments, the row driver 120, the timing controller 140, the analog-to-digital converter (ADC) 133, the ramp signal generator 131 and / or other features of the image sensor 100 may be implemented using a processing circuit (e.g., hardware including a logic circuit), a hardware / software combination (e.g., a processor executing software), or a combination thereof. For example, the processing circuit may more specifically include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a system on a chip (SoC), a programmable logic unit, a microprocessor, an application specific integrated circuit (ASIC), an analog element (e.g., a circuit), an application processor, etc. The buffer 134 may include a volatile memory chip (e.g., a dynamic random access memory (RAM) (DRAM) or a static RAM (SRAM)) or may include a non-volatile memory chip (e.g., a phase change RAM (PRAM), a magnetoresistive RAM (MRAM), a ferroelectric RAM (FeRAM), a resistive RAM (RRAM), a high bandwidth memory (HBM), or a combination thereof).

[0044] An auto focus function can be provided by shielding a portion of a photodiode with metal or the like and detecting only light incident on an unshielded portion of the photodiode in a plurality of pixels PX. However, in a method of detecting a phase difference using metal or the like, light may be reflected by the metal or the like, thereby causing crosstalk between adjacent pixels.

[0045] An image sensor according to an example embodiment may adjust the doping concentration between the substrate and at least one of the photodiodes constituting the pixel group to form a drain terminal connected to the at least one photodiode. Charge generated from the at least one photodiode may not migrate to the floating diffusion region and may be discharged to the drain terminal. Therefore, when the pixel group provides an autofocus function, crosstalk may be limited and / or prevented from occurring.

[0046] Figure 2 and Figure 3 are schematic diagrams of image sensors according to example embodiments.

[0047] Reference Figure 2 , an image forming apparatus 10 according to example embodiments may include a first layer 11 and a second layer 12 disposed below the first layer 11. The first layer 11 and the second layer 12 may be stacked in a direction perpendicular to each other.

[0048] The first layer 11 may have a sensing area SA, a peripheral circuit PC, and a first pad area PA1. In the sensing area SA, a plurality of pixels PX may be disposed. The peripheral circuit PC may be provided with elements for driving the plurality of pixels PX. The first pad area PA1 may be disposed around the sensing area SA and the peripheral circuit PC.

[0049] The first pad area PA1 includes a plurality of upper pads PAD, and the plurality of upper pads PAD may be connected to pads and the logic circuit LC disposed in the second pad area PA2 of the second layer 12 through vias or the like.

[0050] Each of the plurality of pixels PX may include a photodiode receiving light to generate charges, a pixel circuit processing the charges generated from the photodiode, etc. The pixel circuit may include a plurality of transistors for outputting voltages corresponding to the charges generated from the photodiode.

[0051] The first layer 11 may include a plurality of elements for providing a peripheral circuit PC. The plurality of elements included in the peripheral circuit PC may provide a circuit for driving a pixel circuit provided in the first layer 11, for example, a row driver, a column driver, a CDS, an ADC, a timing controller, etc. The plurality of elements included in the peripheral circuit PC may be connected to the pixel circuit through the first pad area PA1 and the second pad area PA2. The peripheral circuit PC may obtain a reset voltage and a pixel voltage from a plurality of pixels PX to generate a pixel signal.

[0052] The second layer 12 may include a logic circuit LC and a second pad area PA2. The logic circuit LC may include a power circuit, an input / output interface, an image signal processor (ISP), etc. The second pad area PA2 may be disposed around the logic circuit LC.

[0053] Reference Figure 3 , an imaging device 20 according to an example embodiment may include a first layer 21 and a second layer 22. The first layer 21 may include a sensing area SA in which a plurality of pixels PX are disposed and a first pad area PA1 disposed around the sensing area SA. The first pad area PA1 may include a plurality of upper pads PAD. The plurality of upper pads PAD may be connected to pads disposed in the second pad area PA2 of the second layer 22, a peripheral circuit PC, and a logic circuit LC through vias or the like.

[0054] Figure 4 The operation of an image sensor according to example embodiments is illustrated.

[0055] Reference Figure 4 , the pixel array PA of the image sensor according to the example embodiment may include a plurality of pixels PX. The plurality of pixels PX may be connected to a plurality of row lines ROW1 to ROWm (ROW) and a plurality of column lines COL1 to COLn (COL). The image sensor may drive the plurality of pixels PX in units of a plurality of row lines ROW. As an example, the time required to drive a selected drive line in the row lines ROW and read a reset voltage and a pixel voltage from the pixel PX connected to the selected drive line may be defined as one horizontal period. The image sensor may operate in a rolling shutter manner in which a plurality of row lines ROW are sequentially driven.

[0056] The frame period FT of the image sensor may be defined as the time required to read the reset voltage and the pixel voltage from all pixels included in the pixel array PA. As an example, the frame period FT may be greater than or equal to the product of the number of row lines ROW and the horizontal period. The shorter the frame period FT of the image sensor, the greater the number of image frames that the image sensor can generate during the same time.

[0057] Figure 5 is a schematic circuit diagram illustrating a pixel included in an image sensor according to example embodiments.

[0058] Reference Figure 5 , a pixel included in the image sensor may include a photodiode PD configured to generate charges in response to light and a pixel circuit configured to process the charges generated from the photodiode PD to output an electrical signal, etc. As an example, the pixel circuit may include a reset transistor RX, a drive transistor DX, a selection transistor SX, a transfer transistor TX, etc.

[0059] The reset transistor RX can be turned on and off by the reset control signal RS. When the reset transistor RX is turned on, the voltage of the floating diffusion area FD can be reset to the power supply voltage VPIX. When the voltage of the floating diffusion area FD is reset, the selection transistor SX can be turned on by the selection control signal SEL to output the reset voltage to the column line COL.

[0060] In an example embodiment, the photodiode PD may generate electrons or holes as main charge carriers by reacting to light. The transfer transistor TX may be turned on and off by a transfer control signal TS. When the transfer transistor TX is turned on after a reset voltage is output to the column line COL, the charge generated by exposing the photodiode PD to light may migrate to the floating diffusion area FD. The drive transistor DX may operate as a source follower amplifier for amplifying the voltage of the floating diffusion area FD. When the selection transistor SX is turned on by a selection control signal SEL, a pixel voltage corresponding to the charge generated from the photodiode PD may be output to the column line COL.

[0061] Each of the reset voltage and the pixel voltage can be detected by a sampling circuit connected to the column line COL. The sampling circuit may include a plurality of samplers having a first input terminal for receiving the reset voltage and a second input terminal for receiving the pixel voltage. The sampler may compare the reset voltage input to the first input terminal with the pixel voltage input to the second input terminal. An analog-to-digital converter ADC may be connected to an output terminal of the sampler, and the analog-to-digital converter may output image data corresponding to a comparison result between the reset voltage and the pixel voltage. The signal processing circuit may use the image data to generate an image.

[0062] Figure 6 The operation of an image sensor according to example embodiments is illustrated.

[0063] Reference Figure 6 , the image sensor 200 according to example embodiments may include a pixel array 210, a row driver 220, and a readout circuit 230. The pixel array 210 may include a plurality of row lines ROW1 to ROWm (ROW) extending in one direction and a plurality of column lines COL1 to COLn (COL) intersecting the plurality of row lines ROW. The row lines ROW and the column lines COL may be connected to pixels PX11 to PXmn, and each of the pixels PX11 to PXmn may include a photodiode and a pixel circuit.

[0064] The row driver 220 may input a transfer control signal, a reset control signal, a selection control signal, etc. to each pixel circuit through the row lines ROW1 to ROWm (ROW). The readout circuit 230 may detect a pixel voltage and a reset voltage from a pixel PX connected to the row line ROW selected by the row driver 220 through the column line COL. The readout circuit 230 may include a sampling circuit 231 configured to output a difference between a pixel voltage and a reset voltage, an analog-to-digital converter 232 configured to convert an output of the sampling circuit 231 into digital data DOUT, and the like.

[0065] The pixel array 210 according to an example embodiment may include a plurality of unit pixels PX11 to PXmn. Each unit pixel of the plurality of unit pixels PX11 to PXmn may include at least one photodiode. A device isolation layer may be formed between the photodiodes. For example, the device isolation layer may have a backside deep trench isolation (BDTI) structure. The device isolation layer may electrically isolate adjacent unit pixels from each other.

[0066] Among the plurality of unit pixels PX11 to PXmn, two or more adjacent unit pixels (e.g., PX11, PX12, PX21, and PX22) may constitute a single pixel group. The unit pixels included in the single pixel group may each include a color filter having the same color. The unit pixels included in the single pixel group may share at least one floating diffusion region.

[0067] The pixel array 210 may include a normal pixel group and an autofocus pixel group. A controller included in the image sensor may generate an image based on a signal generated from the normal pixel group and may provide an autofocus function based on a signal generated from the autofocus pixel group. The number of normal pixel groups may be greater than the number of autofocus pixel groups. The autofocus pixel group may include a pixel group that generates a first image data (e.g., left image data) and a pixel group that generates a second image data (e.g., right image data).

[0068] In an image sensor according to example embodiments, a doping concentration between at least one photodiode included in each auto-focus pixel group and a substrate may be adjusted to form a drain terminal. Charge generated in the at least one photodiode may be discharged to the drain terminal to be limited and / or prevented from migrating to a floating diffusion region. Thus, when the auto-focus pixel group provides an auto-focus function, crosstalk may be limited and / or prevented from occurring.

[0069] Fig. 7A and Figure 7B A pixel array according to an example embodiment is shown.

[0070] Reference Fig. 7A , the pixel array 300 may have a red-green-green-blue (RGGB) pattern. R1 to R4 may each refer to a red pixel, G1 to G4 may each refer to a green pixel, and B1 to B4 may each refer to a blue pixel.

[0071] The first to fourth unit pixels G1 to G4 adjacent to each other may constitute a first pixel group 310. When the first pixel group 310 is a normal pixel group, the first to fourth unit pixels G1 to G4 may each include a green color filter and a microlens ML1. The first to fourth unit pixels G1 to G4 may each include at least one photodiode. The first to fourth unit pixels G1 to G4 may share at least one floating diffusion region.

[0072] The first to fourth unit pixels B1 to B4 adjacent to each other may constitute a second pixel group 320. When the second pixel group 320 is a normal pixel group, the first to fourth unit pixels B1 to B4 may each include a blue color filter and a microlens ML1. The first to fourth unit pixels B1 to B4 may each include at least one photodiode. The first to fourth unit pixels B1 to B4 may share at least one floating diffusion region.

[0073] The first unit pixel G1 to the fourth unit pixel G4 adjacent to each other may constitute the third pixel group 330. When the third pixel group 330 is an auto focus pixel group, the first unit pixel G1 to the fourth unit pixel G4 may each include a green color filter. The first unit pixel G1 to the fourth unit pixel G4 may each include at least one photodiode. The first unit pixel G1 to the fourth unit pixel G4 may share at least one floating diffusion region. The first unit pixel to the fourth unit pixel of the normal pixel group each include a micro lens ML1, while the first unit pixel G1 to the fourth unit pixel G4 of the auto focus pixel group 330 may share a single micro lens ML2.

[0074] exist Fig. 7A , the first unit pixel G1 to the fourth unit pixel G4 included in the third pixel group 330 are shown as each including a green color filter. However, the first unit pixel G1 to the fourth unit pixel G4 included in the third pixel group 330 may each include one of a red color filter and a blue color filter. In addition, a portion of the first unit pixel G1 to the fourth unit pixel G4 included in the third pixel group 330 may include color filters different from each other. For example, a portion of the first unit pixel G1 to the fourth unit pixel G4 included in the third pixel group 330 may each include a green color filter, and the other unit pixels may each include a red color filter.

[0075] The third pixel group 330 may generate one of the first image data (eg, left image data) or the second image data (eg, right image data).

[0076] The microlens ML1 of the normal pixel group and the microlens ML2 of the autofocus pixel group may have different characteristics. For example, the protruding height of the microlens ML1 and the protruding height of the microlens ML2 are the same, but the curvature radius of the microlens ML1 and the curvature radius of the microlens ML2 may be different from each other. According to example embodiments, the protruding height of the microlens ML1 and the protruding height of the microlens ML2 may be different from each other, and the curvature radius of the microlens ML1 and the curvature radius of the microlens ML2 may also be different from each other.

[0077] In an image sensor according to an example embodiment, when four adjacent pixels constitute an autofocus pixel group, the autofocus pixel group may include two autofocus photodiodes and two drain photodiodes. The image sensor may generate the first image data or the second image data using charges generated from the two autofocus photodiodes. The charges generated from the two drain photodiodes may be discharged to a drain terminal connected to the drain photodiode.

[0078] and Fig. 7A The pixel array 300 is different, Figure 7B The pixel array 400 may have a red, green, blue, and white (RGBW) pattern. R1 to R4 may each refer to a red pixel, G1 to G4 may each refer to a green pixel, B1 to B4 may each refer to a blue pixel, and W1 to W4 may each refer to a white pixel.

[0079] The first to fourth unit pixels W1 to W4 included in the third pixel group 330 (auto focus pixel group) may each include a white color filter. However, example embodiments are not limited thereto, and the first to fourth unit pixels W1 to W4 included in the third pixel group 330 may each include one of a green color filter, a red color filter, and a blue color filter.

[0080] In addition, a portion of the first to fourth unit pixels W1 to W4 included in the third pixel group 330 may include color filters different from each other. For example, a portion of the first to fourth unit pixels W1 to W4 included in the third pixel group 330 may each include a green color filter, and the other unit pixels may each include a white color filter.

[0081] Figure 8 is a schematic circuit diagram illustrating a pixel group according to example embodiments.

[0082] Reference Figure 8, a pixel group according to an example embodiment may include first to fourth photodiodes PD1 to PD4, first to fourth transfer transistors TX1 to TX4, a reset transistor RX, a drive transistor DX, and a selection transistor SX. The first transfer transistor TX1 may be connected to the first photodiode PD1, and the second transfer transistor TX2 may be connected to the second photodiode PD2. The third transfer transistor TX3 may be connected to the third photodiode PD3, and the fourth transfer transistor TX4 may be connected to the fourth photodiode PD4. A first unit pixel including the first photodiode PD1, a second unit pixel including the second photodiode PD2, a third unit pixel including the third photodiode PD3, and a fourth unit pixel including the fourth photodiode PD4 may be shared by a single floating diffusion region FD.

[0083] The first transfer control signal TS1 may be a first turn-on signal for turning on the first transfer transistor TX1, and the first transfer transistor TX1 may be turned on in response to the first transfer control signal TS1. The second transfer control signal TS2 may be a second turn-on signal for turning on the second transfer transistor TX2, and the second transfer transistor TX2 may be turned on in response to the second transfer control signal TS2. Conversely, the third transfer control signal TS3 may be a first turn-off signal for turning off the third transfer transistor TX3, and the third transfer transistor TX3 may be turned off in response to the third transfer control signal TS3. The fourth transfer control signal TS4 may be a second turn-off signal for turning off the fourth transfer transistor TX4, and the fourth transfer transistor TX4 may be turned off in response to the fourth transfer control signal TS4. For example, the first turn-off signal and the second turn-off signal may each be a ground voltage.

[0084] exist Figure 8 In the embodiment, four photodiodes and four transfer gate electrodes are shown and described as being separated from each other. However, at least two photodiodes may be connected to each other to constitute a single photodiode, and at least two transfer gate electrodes may be connected to each other to constitute a single transfer gate electrode.

[0085] when Figure 8 When the pixel group shown is an autofocus pixel group, the pixel group may include two autofocus photodiodes PD1 and PD2 and two drain photodiodes PD3 and PD4. The image sensor may generate the first image data or the second image data using the charges generated from the two autofocus photodiodes PD1 and PD2. The image sensor may discharge the charges generated from the drain photodiodes PD3 and PD4 to the drain terminal connected to the drain photodiode.

[0086] Specifically, the image sensor may turn on the first transfer transistor TX1 and the second transfer transistor TX2 at the same time. When the first transfer transistor TX1 and the second transfer transistor TX2 are turned on at the same time, charges output from the first photodiode PD1 and the second photodiode PD2 may be added in the floating diffusion area FD.

[0087] When the selection transistor SX is subsequently turned on in response to the selection control signal SEL, the readout circuit can detect a pixel voltage corresponding to the amount of charge added in the floating diffusion area FD through the column line COL.

[0088] The image sensor may turn off the third transfer transistor TX3 and the fourth transfer transistor TX4. The image sensor may connect the power supply voltage V PIX The image sensor can also apply the power supply voltage V between the fourth photodiode PD4 and the fourth transfer transistor TX4. PIX is applied to the fourth photodiode PD4. In the present application, although the power supply voltage V PIX is applied to the third photodiode PD3 and the fourth photodiode PD4, but a constant voltage or a positive (+) voltage may be applied to the third photodiode PD3 and the fourth photodiode PD4. PIX When applied to the third photodiode PD3 and the fourth photodiode PD4 , it is possible to restrict and / or prevent charges outputted from each of the third photodiode PD3 and the fourth photodiode PD4 from migrating to the floating diffusion area FD.

[0089] Fig. 9A is a plan view of a general pixel group according to example embodiments. Fig. 9A The pixel group can be Fig. 7A One of the pixel groups 310 to 350.

[0090] Reference Fig. 9A The pixel group PG may include first to fourth photodiodes PD1 to PD4, first to fourth transfer gate electrodes TG1 to TG4, a selection transistor SX, a drive transistor DX, a reset transistor RX, and a dummy transistor DMX. The first to fourth photodiodes PD1 to PD4 may share a floating diffusion region FD.

[0091] The first transfer gate electrode TG1 may be a gate electrode of a first transfer transistor connected to the first photodiode PD1, the second transfer gate electrode TG2 may be a gate electrode of a second transfer transistor connected to the second photodiode PD2, the third transfer gate electrode TG3 may be a gate electrode of a third transfer transistor connected to the third photodiode PD3, and the fourth transfer gate electrode TG4 may be a gate electrode of a fourth transfer transistor to which the fourth photodiode PD4 is connected.

[0092] The pixel group PG may share a selection transistor SX, a drive transistor DX, a reset transistor RX, and a dummy transistor DMX.

[0093] The dummy transistor DMX may be used to separate the node of the floating diffusion area FD from the charge output node of the adjacent pixel group. According to example embodiments, a device isolation layer such as shallow trench isolation (STI) may be used instead of the dummy transistor DMX. According to example embodiments, a PN junction may be used instead of a dummy transistor DMX to isolate the node of the floating diffusion area FD from the charge output node of the adjacent pixel group. For example, the node of the floating diffusion area FD may be doped with an n-type, and the active area of ​​the charge output node of the adjacent pixel group may also be doped with an n-type. Therefore, a p-type impurity may be introduced between the node of the floating diffusion area FD and the charge output node of the adjacent pixel group to isolate the node of the floating diffusion area FD from the charge output node of the adjacent pixel group.

[0094] exist Fig. 9A In the embodiment, four photodiodes and four transfer gate electrodes separated from each other are shown and described. However, at least two photodiodes may be connected to each other to form a single photodiode, and at least two transfer gate electrodes may be connected to each other to form a single transfer gate electrode. When at least two transfer gate electrodes are connected to each other to form a single transfer gate electrode, the number of contacts connected to the transfer gate electrode may be reduced.

[0095] According to the first embodiment, the pixel group PG may have a first structure in which the first transfer gate electrode TG1 and the second transfer gate electrode TG2 are connected to each other to constitute a single transfer gate electrode, and the third transfer gate electrode and the fourth transfer gate electrode TG4 are connected to each other to constitute a single transfer gate electrode. Alternatively, the pixel group PG may have a second structure in which the first photodiode PD1 and the second photodiode PD2 are connected to each other to constitute a single photodiode, and the third photodiode PD3 and the fourth photodiode PD4 are connected to each other to constitute a single photodiode. Alternatively, the pixel group PG may have both the first structure and the second structure.

[0096] According to the second embodiment, the pixel group PG may have a third structure in which the first transfer gate electrode TG1 and the third transfer gate electrode TG3 are connected to each other to constitute a single transfer gate electrode, and the second transfer gate electrode TG2 and the fourth transfer gate electrode TG4 are connected to each other to constitute a single transfer gate electrode. Alternatively, the pixel group PG connects the first photodiode PD1 with the third photodiode PD3 to constitute a single photodiode, and connects the second photodiode PD2 with the fourth photodiode PD4. The fourth structure may be connected so as to constitute a single photodiode. Alternatively, the pixel group PG may have both the third structure and the fourth structure.

[0097] According to the first embodiment, when the pixel group PG is an auto focus pixel group, the pixel group PG may acquire auto focus information from left and right photodiodes. According to the second exemplary embodiment, when the pixel group PG is an auto focus pixel group, the pixel group PG may acquire auto focus information from upper and lower photodiodes.

[0098] According to the third embodiment, when the pixel group PG is a normal pixel group, the pixel group PG may have a fifth structure in which the first transfer gate electrode TG1, the second transfer gate electrode TG2, the third transfer gate electrode TG3, and the fourth transfer gate electrode TG4 are connected to each other to constitute a single transfer gate electrode, and the first photodiode PD1, the second photodiode PD2, the third photodiode PD3, and the fourth photodiode PD4 are connected to each other to constitute a single photodiode.

[0099] According to the third embodiment, the image sensor may detect only the pixel voltage corresponding to the amount of added charges output from the first to fourth photodiodes PD1 to PD4 .

[0100] Fig. 9B and Fig. 9C are plan views of an auto-focus pixel group according to an example embodiment. Fig. 9A Simultaneous description of the differences of common pixel groups Fig. 9B and the auto-focus pixel group of FIG. 9C. The auto-focus pixel group according to example embodiments may include a first pixel region and a second pixel region. The first photodiode PD1 included in the first unit pixel and the second photodiode PD2 included in the second unit pixel may constitute a first photodiode group PG1 in the first pixel region. The third photodiode PD3 included in the third unit pixel and the fourth photodiode PD4 included in the fourth unit pixel may constitute a second photodiode group PG2 in the second pixel region.

[0101] Specifically, refer to Fig. 9B, the auto focus pixel group 330a may generate the first image data (e.g., left image data). In this case, the auto focus pixel group 330a may acquire the first image data using the charges output from the first photodiode PD1 and the second photodiode PD2 included in the first photodiode group PG1. The first photodiode PD1 and the second photodiode PD2 may be an auto focus photodiode group.

[0102] Charges output from the third photodiode PD3 and the fourth photodiode PD4 included in the second photodiode group PG2 may be discharged to at least one drain terminal. The at least one drain terminal may be connected to the third photodiode PD3 and the fourth photodiode PD4. The third photodiode PD3 and the fourth photodiode PD4 may be a drain photodiode group.

[0103] Reference Fig. 9C , the auto focus pixel group 330b may generate the second image data (e.g., right image data). In this case, the auto focus pixel group 330b may acquire the second image data using the charges output from the third photodiode PD3 and the fourth photodiode PD4 included in the second photodiode group PG2. The third photodiode PD3 and the fourth photodiode PD4 may be an auto focus photodiode group.

[0104] Charges output from the first photodiode PD1 and the second photodiode PD2 included in the first photodiode group PG1 may be discharged to at least one drain terminal. The at least one drain terminal may be connected to the first photodiode PD1 and the second photodiode PD2. The first photodiode PD1 and the second photodiode PD2 may be a drain photodiode group.

[0105] The image sensor may perform an auto focus function using the first image data and the second image data generated from the auto focus pixel groups 330 a and 330 b .

[0106] Since the structure and operation of the auto focus pixel group for generating the first image data are similar to the structure and operation of the auto focus pixel group for generating the second image data, an example of the auto focus pixel for generating the second image data will now be described.

[0107] FIG. 10A to FIG. 10F The operation of an auto-focus pixel group according to an example embodiment is shown.

[0108] Fig. 10A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 10B is along Fig. 10A The cross-sectional view taken along the line I-I' in FIG. Fig. 10Cshows potential levels of an image sensor in a photon integration mode according to example embodiments, FIG. 10D to FIG. 10F is a cross-sectional view illustrating a portion of an auto-focus pixel group according to example embodiments.

[0109] Reference Fig. 10A , the auto focus pixel group 330-1 may include a first photodiode PD1 and a second photodiode PD2 formed in a first pixel region, a third photodiode PD3 and a fourth photodiode PD4 formed in a second pixel region, a first drain terminal DN1 connected to the third photodiode PD3, and a second drain terminal DN2 connected to the fourth photodiode PD4. The first to fourth photodiodes PD1 to PD4 may be doped with n-type, and the first drain terminal DN1 and the second drain terminal DN2 may be doped with n-type.

[0110] Reference Fig. 10B The auto focus pixel group 330-1 may include a second photodiode PD2, a second color filter CF2 disposed on the second photodiode PD2, a fourth photodiode PD4, a fourth color filter CF4 disposed on the fourth photodiode PD4, a device isolation layer 331, a pixel circuit 333, a floating diffusion region FD, and a second drain terminal DN2.

[0111] The device isolation layer 331 can electrically isolate the first pixel region from the second pixel region. For example, the device isolation layer 331 can electrically isolate the second photodiode PD2 and the fourth photodiode PD4 disposed adjacent to each other. The floating diffusion region FD can store charges generated from each of the second photodiode PD2 and the fourth photodiode PD4. The pixel circuit 333 can include a second transfer gate electrode TG2, a fourth transfer gate electrode TG4, and a metal interconnect.

[0112] The transfer control signal VTG may be input to the second transfer gate electrode TG2 of the second transfer transistor connected to the second photodiode PD2 in the first pixel region. Thus, the second transfer transistor may be turned on. When the second transfer transistor is turned on, charges generated in the second photodiode PD2 may be discharged to the floating diffusion region FD.

[0113] The barrier voltage V PB The barrier voltage may refer to a voltage for forming a sufficient barrier between the fourth photodiode PD4 and the floating diffusion area FD. The power supply voltage V may be applied to the fourth transfer gate electrode TG4 of the fourth transfer transistor connected to the fourth photodiode PD4 in the second pixel area. PIX is input to the second drain terminal DN2 of the second pixel region. PIXWhen the power supply voltage V PIX The charges generated in the fourth photodiode PD4 may not migrate to the floating diffusion area FD due to a potential barrier but may migrate to a power supply node.

[0114] Reference Fig. 10C , the potential level is a negative potential in the upward direction and a positive potential in the downward direction. The potential level may decrease in the upward direction and may increase in the downward direction.

[0115] Reference Fig. 10B and Fig. 10C , when a barrier voltage is applied to the fourth transfer gate electrode TG4 to form a sufficient potential barrier between the fourth photodiode PD4 and the floating diffusion area FD, the channel region under the fourth transfer gate electrode TG4 may have a first potential level V1. The second photodiode PD2 and the fourth photodiode PD4 may each have a second potential level V2. When the second transfer transistor is turned on, the channel region under the second transfer gate electrode TG2 may have a third potential level V3. The floating diffusion area FD and the second drain terminal DN2 may each have a fourth potential level V4. The potential level of the floating diffusion area FD and the potential level of the second drain terminal DN2 may be different from each other.

[0116] The first potential level V1 may be lower than the second potential level V2, the second potential level V2 may be lower than the third potential level V3, and the third potential level V3 may be lower than the fourth potential level V4.

[0117] Charges (−) generated in the second photodiode PD2 due to a difference between the potential level of the second photodiode PD2 and the potential level of the channel region under the second transfer gate electrode TG2 may migrate to the floating diffusion area FD through the first path P1 .

[0118] However, due to the difference between the potential level of the fourth photodiode PD4 and the potential level of the channel region under the fourth transfer gate electrode TG4, a potential barrier PB may be set between the fourth photodiode PD4 and the floating diffusion area FD. Therefore, the charge (-) generated in the fourth photodiode PD4 may not migrate to the floating diffusion area FD, but may be discharged to the second drain terminal DN2 through the second path P2.

[0119] According to an example embodiment, Fig. 10AThe auto focus pixel group 330 may not include the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4. When the potential barrier between the third photodiode PD3 and the floating diffusion area FD and the potential barrier between the fourth photodiode PD4 and the floating diffusion area FD are formed to be sufficiently high, even in the case where the third transfer gate electrode and the fourth transfer gate electrode are not provided, the charges generated in the third photodiode PD3 and the fourth photodiode PD4 may not migrate to the floating diffusion area FD but may be discharged to the drain terminals DN1 and DN2.

[0120] Reference Fig. 10D ,and FIG. 10A to FIG. 10C The auto-focus pixel group 330-1 is different from Fig. 10D The auto-focus pixel group 330c has a second pixel region, in which at least one of the third unit pixel and the fourth unit pixel may not have a drain terminal. For example, the fourth unit pixel may not have a drain terminal. Alternatively, a metal may be further provided between the fourth color filter CF4 of the fourth unit pixel and the microlens ML2. Light incident on the fourth photodiode PD4 may be blocked by the metal. Therefore, even when the fourth unit pixel does not have a drain terminal, the auto-focus pixel group may generate image data for performing an auto-focus function.

[0121] and Fig. 10D Different from the autofocus pixel group 330c, Fig.10E The auto-focus pixel group has a second pixel region, and the second pixel region may include at least one of a third photodiode and a fourth photodiode. For example, the second pixel region may not include the fourth photodiode PD4.

[0122] and Fig.10E The autofocus pixel group of 330d is different, Fig.10F The auto focus pixel group 330e is an auto focus pixel group in which metal or the like may not be provided between the micro lens ML2 and the fourth color filter CF4 of the fourth unit pixel. Instead, the fourth unit pixel of the second pixel region may further have a drain terminal DN2. A power supply voltage may be applied to the drain terminal DN2. The device isolation layer 331 may physically completely isolate the second unit pixel and the fourth unit pixel from each other.

[0123] The device isolation layer 331 may refer to a DTI region extending (or formed) from the first surface (or lower portion) of the semiconductor substrate SL in a vertical direction. In addition, the device isolation layer 331 may refer to a DTI formed in the process of manufacturing a back-illuminated (BSI) image sensor. The device isolation layer 331 may prevent crosstalk between one pixel and another pixel.

[0124] When the semiconductor substrate SL of the fourth unit pixel is formed of silicon, charges may be generated in the semiconductor substrate SL of the fourth unit pixel by light. Since the device isolation layer 331 may physically completely isolate one pixel from another pixel, the charges generated in the semiconductor substrate SL of the fourth unit pixel by light may not migrate to the adjacent second unit pixel, but may be discharged to the second drain terminal DN2.

[0125] As reference FIG. 10A to FIG. 10D As described above, the number of photodiodes included in the second pixel region may be the same as the number of photodiodes included in the first pixel region. Fig.10E and Fig.10F As described, the number of photodiodes included in the second pixel region may be smaller than the number of photodiodes included in the first pixel region. According to example embodiments, the second pixel region may not include a photodiode.

[0126] exist FIG. 10A to FIG. 10D In the present invention, a single pixel group including two auto-focus photodiodes and two drain photodiodes has been shown and described. However, a single pixel group may include at least one auto-focus photodiode and at least one drain photodiode.

[0127] Fig.11A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 11B is along Fig.11A The cross-sectional view taken along the line II-II' in FIG. Fig. 11C is along Fig.11A A cross-sectional view taken along line III-III'.

[0128] and Fig. 10A The auto-focus pixel group 330-1 is different from Fig.11A The auto focus pixel group 330-2 is an auto focus pixel group in which the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4 can be connected to each other to form a single transfer gate electrode TG3'. In addition, the third photodiode PD3 and the fourth photodiode PD4 can be connected to each other to form a single photodiode PD3'. A single drain terminal DN can be connected to the photodiode PD3'.

[0129] The photodiode PD3' may have a shape different from that of each of the first photodiode PD1 and the second photodiode PD2. In addition, the photodiode PD3' may have an area different from that of each of the first photodiode PD1 and the second photodiode PD2. For example, the area of ​​the photodiode PD3' may be larger than that of each of the first photodiode PD1 and the second photodiode PD2. In this case, the light receiving area of ​​the photogate electrode TG3' may be larger than that of each of the first photodiode PD1 and the second photodiode PD2.

[0130] Reference Fig. 11B , the third photodiode PD3 and the fourth photodiode PD4 may be connected to each other to form a single photodiode PD3', and a single drain terminal DN may be connected to the photodiode PD3'. PIX input to the drain terminal DN. When the power supply voltage V PIX When input to the drain terminal DN, the charges generated from the photodiode PD3 ′ may be discharged to the drain terminal DN.

[0131] Reference Fig. 11C The transfer gate electrode TG3' may be disposed between the floating diffusion region FD and the drain terminal DN. The floating diffusion region FD may be doped with an n-type, and the drain terminal DN may be doped with an n-type. + type. The barrier voltage V PB The power supply voltage V PIX Therefore, the charges generated in the photodiode PD3' may not migrate to the floating diffusion area FD but may be discharged to the drain terminal DN.

[0132] In the absence of the transfer gate electrode TG3' between the floating diffusion area FD and the drain terminal DN, when a sufficient potential barrier is not formed between the floating diffusion area FD and the photodiode PD3', a portion of charges generated in the photodiode PD3' may migrate to the floating diffusion area FD.

[0133] According to example embodiments, the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4 may be connected to each other to constitute a single transfer gate electrode TG3′, and the barrier voltage V PB Input to the transfer gate electrode TG3'. When the barrier voltage V PBWhen input to the transfer gate electrode TG3', a high potential barrier can be formed between the floating diffusion area FD and the photodiode PD3'. Therefore, the charges generated in the photodiode PD3' will have difficulty migrating to the floating diffusion area FD. As a result, the effect of discharging the charges generated in the photodiode PD3' to the drain terminal DN can be significantly improved.

[0134] Fig. 12A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 12B is along Fig. 12A A cross-sectional view taken along line IV-IV'.

[0135] and Fig.11A The auto-focus pixel group 330-2 is different. Fig. 12A The auto focus pixel group 330-3 may further include a ground terminal GN. The ground terminal GN may provide a ground voltage to a unit pixel included in the pixel array.

[0136] A ground terminal GN may be provided in each common pixel group. + When the n-type ground terminal GN is close to the n-type photodiode, the dark current may increase. When the dark current increases, the signal detected even when light is not irradiated (dark level) increases. When the dark level increases, the ground terminal GN may act as a factor causing noise in the image sensor.

[0137] In the image sensor according to the example embodiment, the ground terminal GN may be provided in each auto focus pixel group which is smaller in number than the normal pixel group. Therefore, the number of factors causing noise in the image sensor may be reduced. Even when the ground terminal GN is provided in each auto focus pixel group, a sufficient ground voltage may be provided to the unit pixel included in the pixel array.

[0138] Reference Fig. 12B , the barrier voltage V PB The power supply voltage V PIX The ground voltage GND may be input to the drain terminal DN, and the ground voltage GND may be input to the ground terminal GN. When the ground voltage GND is input to each ground terminal GN included in the auto focus pixel group, the ground voltage GND may be provided to the unit pixel included in the pixel array.

[0139] Fig.13A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 13B is along Fig.13A Cross-sectional view taken along line V-V'.

[0140] Reference Fig.13A ,and Fig. 12A The auto-focus pixel group 330-3 is different. Fig.13A The auto focus pixel group 330-4 is an auto focus pixel group in which the ground terminal GN is provided in a region including a region where the drain photodiode PD3" is formed, rather than in a region including a region where the auto focus photodiodes PD1 and PD2 are formed. + Type drain terminal DN and p + When the drain terminal DN is close to the ground terminal GN, the electric field between the drain terminal DN and the ground terminal GN may increase. When the electric field increases, image defects (eg, white spots) may occur.

[0141] In an image sensor according to an example embodiment, a transfer gate electrode TG3" extending from a photodiode PD3" may be formed. For example, the transfer gate electrode TG3" may have a Y shape. The transfer gate electrode TG3" may extend from the photodiode PD3" to be disposed between the drain terminal DN and the ground terminal GN. The transfer gate electrode TG3" disposed between the drain terminal DN and the ground terminal GN may prevent an increase in an electric field between the drain terminal DN and the ground terminal GN.

[0142] In addition, when the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4 are separately provided, a contact may be respectively provided on the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4. The contact may be connected to the metal layer. However, when the third transfer gate electrode TG3 and the fourth transfer gate electrode TG4 are connected to each other to form a single transfer gate electrode TG3″ and the transfer gate electrode TG3″ extends from the photodiode PD3″, a single contact may be provided on the transfer gate electrode TG3″. The contact may be connected to the metal layer.

[0143] Reference Fig. 13B , Fig. 13B The photodiode PD3 ″ of the auto-focus pixel group 330 - 4 may include a first region S1 and a second region S2 . The first region S1 may be disposed on the ground terminal GN, and the second region S2 may be disposed on the drain terminal DN.

[0144] The first region S1 may have a thickness T1 different from the thickness T2 of the second region S2. For example, the thickness T1 of the first region S1 may be less than the thickness T2 of the second region S2. In this case, the upper surface UP1 of the first region S1 may have the same depth as the upper surface UP2 of the second region S2, and the lower surface LP1 of the first region S1 may have a different depth from the lower surface LP2 of the second region S2.

[0145] The barrier voltage V PB The power supply voltage V PIXBy inputting to the drain terminal DN, the ground voltage GND can be input to the ground terminal GN.

[0146] Fig.14A is a plan view of an auto-focus pixel group according to an example embodiment, Fig. 14B is along Fig.14A A cross-sectional view taken along line VI-VI'.

[0147] Reference Fig.14A The auto focus pixel group 330-5 may have a first drain terminal DN1 connected to the third photodiode PD3 and a second drain terminal DN2 connected to the fourth photodiode PD4. A ground terminal GN may be provided between the first drain terminal DN1 and the second drain terminal DN2.

[0148] and Fig.13A The autofocus pixel groups are different. Fig.14A The autofocus pixel group may have the same layout of drain photodiodes PD3 and PD4 and transfer gate electrodes TG3 and TG4 as a normal pixel group. Therefore, it may be advantageous in terms of process management.

[0149] Reference Fig. 14B , the first power supply voltage V PIX 1 is input to the first drain terminal DN1 connected to the third photodiode PD3, and the second power supply voltage V PIX 2 is input to the second drain terminal DN2 connected to the fourth photodiode PD4. The ground voltage GND can be input to the ground terminal GN.

[0150] Fig.15 is a plan view of an auto-focus pixel group according to an example embodiment. Fig.14A The autofocus pixel group 330-5 is different. Fig.15 The auto focus pixel group 330-6 may not include the third transfer gate electrode and the fourth transfer gate electrode. This is because, when the potential barrier between the third photodiode PD3 and the floating diffusion area FD and the potential barrier between the fourth photodiode PD4 and the floating diffusion area FD are formed to be sufficiently high, the charges generated in the third photodiode PD3 and the fourth photodiode PD4 do not migrate to the floating diffusion area FD, but can be discharged to the terminals DN1 and DN2.

[0151] Fig.16 shows a pixel array according to an example embodiment, Fig.17 is a plan view of an auto-focus pixel group according to example embodiments.

[0152] Reference Fig.16, the third pixel group 330' and the fifth pixel group 350' adjacent to each other in the pixel array 500 may each be an autofocus pixel group. For example, the third pixel group 330' may generate first image data (e.g., left image data), and the fifth pixel group 350' may generate second image data (e.g., right image data).

[0153] Reference Fig.16 and Fig.17 , the third photodiode PD3 of the third pixel group 330' and the first photodiode PD1 of the fifth pixel group 350' may be connected to each other to constitute the photodiode PD3'. Therefore, a single first drain terminal DN1 may be connected to the photodiode PD3'.

[0154] In addition, the fourth photodiode PD4 of the third pixel group 330' and the second photodiode PD2 of the fifth pixel group 350' may be connected to each other to constitute a single photodiode PD4'. Therefore, a single second drain terminal DN2 may be connected to the photodiode PD4'.

[0155] The ground terminal GN may be provided between the first drain terminal DN1 and the second drain terminal DN2 .

[0156] Fig.18 is a partial cross-sectional view of a pixel according to example embodiments.

[0157] Reference Fig.18 , the third pixel group 330 of the pixel array 600 may be an auto focus pixel group. The second unit pixel of the third pixel group 330 may include a second photodiode PD2 and a color filter CF2, and the fourth unit pixel of the third pixel group 330 may include a fourth photodiode PD4 and a color filter CF4. The second unit pixel and the fourth unit pixel of the third pixel group 330 may share a single micro lens ML2. The second photodiode PD2 of the third pixel group 330 may be an auto focus photodiode, and the fourth photodiode PD4 of the third pixel group 330 may be a drain photodiode.

[0158] The fourth pixel group 340 and the fifth pixel group 350 may each be a normal pixel group. The fourth unit pixel of the fourth pixel group 340 may include a fourth photodiode PD4, a fourth color filter CF4, and a microlens ML1. The second unit pixel of the fifth pixel group 350 may include a second photodiode PD2, a second color filter CF2, and a microlens ML1.

[0159] A BDTI structure vertically extending from the first surface LP of the semiconductor substrate SL may be formed between unit pixels. A second drain terminal DN2 may be formed between the fourth photodiode PD4 of the third pixel group 330 and the second surface UP of the semiconductor substrate SL by increasing n-type doping concentration.

[0160] The transfer control signal V TG The second transfer gate electrode TG2 of the second transfer transistor connected to the second photodiode PD2 of the third pixel group 330 is input. Therefore, the second transfer transistor can be turned on. When the second transfer transistor is kept in the on state, the potential level of the channel region under the second transfer gate electrode TG2 is higher than the potential level of the second photodiode PD2, and therefore, the charges generated in the second photodiode PD2 can migrate to the floating diffusion area FD.

[0161] The barrier voltage V PB The power supply voltage V PIX Input to the second drain terminal DN2. Therefore, due to the difference between the potential level of the fourth photodiode PD4 and the potential level of the channel region under the fourth transfer gate electrode TG4, a potential barrier may be set between the fourth photodiode PD4 and the floating diffusion area FD. Charges generated in the fourth photodiode PD4 may not migrate to the floating diffusion area FD due to the potential barrier, but may be discharged to the second drain terminal DN2. According to example embodiments, the third pixel group 330 may not include the fourth transfer gate electrode TG4.

[0162] The image sensor may generate the first image data or the second image data using the charges generated in the second photodiode PD2 of the third pixel group 330. The image sensor may perform an auto focus function using the first image data and the second image data.

[0163] The image sensor may generate image data using charges generated in the fourth photodiode PD4 of the fourth pixel group 340 and the second photodiode PD2 of the fifth pixel group 350. The image sensor may generate an image using the image data.

[0164] Fig.19A and Fig.19B The sensitivity of an image sensor according to example embodiments is shown.

[0165] Reference Fig.19A and Fig.19B, the X-axis may represent the illuminance (LUX), and the Y-axis may represent the output of the analog-to-digital converter, such as a digital signal. There may be an allowable range in the analog input value that may be converted by the analog-to-digital converter. When an input that may exceed the allowable range is applied, the input may have a saturation value SAT within the electrically allowable range. For example, the analog-to-digital converter may represent a resolution of up to 10 bits. In this case, the analog-to-digital converter may output 0 to 1023 LSBs, and the saturation value SAT may be 1023 LSBs.

[0166] exist Fig.19A and Fig.19B , graph "a" may represent a first signal S1 generated from a normal pixel group, and graph "b" may represent a second signal S2 generated from an autofocus pixel group. The first signal S1 may correspond to the added charge amount output from four photodiodes included in the normal pixel group. The second signal S2 may correspond to the added charge amount output from two autofocus photodiodes included in the autofocus pixel group.

[0167] like Fig.19A As shown in FIG. 1 , the sensitivity of the autofocus pixel group can be less than the sensitivity of the normal pixel group. Fig.19B As shown in curve “c”, when the sensitivity of the autofocus pixel group increases the sensitivity of the ordinary pixel group, the sensitivity of the ordinary pixel group and the sensitivity of the autofocus pixel group may be substantially the same.

[0168] For example, the conversion gain CG applied when the charge generated in the photodiode included in the autofocus pixel group is converted into a voltage can be adjusted. For example, the conversion gain of the charge generated in the photodiode included in the autofocus pixel group can be greater than the conversion gain of the charge generated in the photodiode included in the normal pixel group.

[0169] As a first embodiment, the distance between the metal layer connected to the floating diffusion region and the metal layer around the floating diffusion region in the auto-focus pixel group may be adjusted.

[0170] For example, the shorter the distance between the first metal layer connected to the floating diffusion region and the metal layer surrounding the first metal layer, the higher the capacitance between the metal layers. Therefore, the conversion gain CG of the photodiode can be reduced. However, the longer the distance between the metal layer connected to the floating diffusion region and the metal layer surrounding the metal layer, the lower the capacitance between the metal layers. Therefore, the conversion gain CG of the photodiode can be increased.

[0171] For example, the distance between the first metal layer connected to the floating diffusion region of the normal pixel group and the metal layer surrounding the metal layer may be shorter than the distance between the second metal layer connected to the floating diffusion region of the autofocus pixel group and the metal layer surrounding the second metal layer. Therefore, the sensitivity of the normal pixel group and the sensitivity of the autofocus pixel group may be substantially the same.

[0172] As a second embodiment, at least one of the width and length of the metal layer connected to the floating diffusion area can be adjusted. For example, the width of the second metal layer connected to the floating diffusion area of ​​the autofocus pixel group can be smaller than the width of the first metal layer connected to the floating diffusion area of ​​the normal pixel group. The smaller the width of the metal layer connected to the floating diffusion area, the more the conversion gain CG of the photodiode can be increased. In addition, the length of the second metal layer connected to the floating diffusion area of ​​the autofocus pixel group can be smaller than the length of the first metal layer connected to the floating diffusion area of ​​the normal pixel group. The shorter the length of the metal layer connected to the floating diffusion area, the more the conversion gain CG of the photodiode can be increased.

[0173] As a third embodiment, when the color filter of each unit pixel included in the auto focus pixel group is a white filter, the sensitivity of the photodiode can be increased.

[0174] As a fourth embodiment, the concentration of impurities injected into the floating diffusion region can be adjusted. For example, the concentration of impurities injected into the floating diffusion region of the autofocus pixel group can be lower than the concentration of impurities injected into the floating diffusion region of the normal pixel group. The lower the concentration of the floating diffusion region, the more the conversion gain CG of the photodiode can be increased.

[0175] In the present application, a single pixel group including two auto-focus photodiodes and two drain photodiodes has been illustrated and described. However, a single pixel group may include at least one auto-focus photodiode and at least one drain photodiode.

[0176] Fig. 20 is a schematic block diagram of an electronic device including an image sensor according to example embodiments.

[0177] according to Fig. 20 The electronic device 1000 of the illustrated exemplary embodiment may include an image sensor 1010, an input / output device 1020, a memory 1030, a processor 1040, a port 1050, etc. In addition, the electronic device 1000 may also include a wired / wireless communication device, a power supply, etc. Fig. 20Among the components shown, port 1050 may be an element for communicating with a video card, sound card, memory card, USB card, etc. In addition to a general desktop computer or laptop computer, electronic device 1000 may also be a smart phone, a tablet personal computer (PC), a smart wearable device, etc.

[0178] The processor 1040 may perform specific operations, commands, tasks, etc. In some embodiments, the processor 1040 may be implemented with a processing circuit (e.g., hardware including a logic circuit), a hardware / software combination (e.g., a processor that executes software), or a combination thereof. For example, the processing circuit may more specifically include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a system on a chip (SoC), a programmable logic unit, a microprocessor, an application specific integrated circuit (ASIC), an analog element (e.g., a circuit), an application processor, etc. The processor 1040 may be a central processing unit (CPU), a microprocessor unit (MCU), a system on a chip (SoC), etc., and the processor 1040 may communicate with the image sensor 1010, the input / output device 1020, and the memory 1030 through the bus 1060, as well as other devices connected to the port 1050.

[0179] The memory 1030 may be a storage medium for storing data, multimedia data, etc. used for the operation of the electronic device 1000. The memory 1030 may include a volatile memory such as a random access memory (RAM) or a non-volatile memory such as a flash memory. The memory 1030 may also include a solid state drive (SSD), a hard disk drive (HDD), or an optical disk drive (ODD) as a storage device. Input and output devices may also be included in the electronic device 1000 or connected to the electronic device 1000, and may include input devices such as a keyboard, a mouse, a touch screen, etc. and output devices such as a display provided to a user, an audio output unit, etc.

[0180] The image sensor 1010 may be mounted on a package substrate and may be connected to the processor 1040 via a bus 1060 or via another communication means. The image sensor 1010 may be as described in reference Figures 1 to 19B The exemplary embodiment described herein is employed in electronic device 1000 .

[0181] As described above, a drain terminal connected to at least one of the photodiodes constituting the pixel group can be formed by adjusting the doping concentration between the at least one photodiode and the substrate. The charge generated in the at least one photodiode may not migrate to the floating diffusion area, but may be discharged to the drain terminal. As a result, when the pixel group provides an autofocus function, crosstalk may be limited and / or prevented from occurring.

[0182] While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of the inventive concept as defined by the appended claims.

Claims

1. An image sensor, comprising: a first photodiode group including a first photodiode and a second photodiode and a second photodiode group including a photodiode; a first transfer transistor group including a first transfer transistor connected to the first photodiode of the first photodiode group and a second transfer transistor connected to the second photodiode of the first photodiode group; a floating diffusion region of a substrate, the floating diffusion region configured to store charges generated in the first photodiode group when at least one of the first transfer transistor and the second transfer transistor of the first transfer transistor group is turned on; as well as a power node connected to the second photodiode group, the power node being configured to have a power voltage applied thereto so as to apply the power voltage to the second photodiode group, the power voltage causing charges generated in the second photodiode group to migrate to the power node; as well as a second transfer transistor group including at least one transfer transistor connected to the second photodiode group, wherein the at least one transfer transistor of the second transfer transistor group is configured to have a barrier voltage applied thereto, and The barrier voltage forms a potential barrier between the second photodiode group and the floating diffusion region.

2. The image sensor according to claim 1, further comprising: a device isolation layer electrically isolating the second photodiode of the first photodiode group and one of the photodiodes of the second photodiode group from each other; as well as a drain terminal connected to the second photodiode group, The image sensor is configured to discharge the charge generated from the second photodiode group to the drain terminal in response to applying the power supply voltage to the drain terminal.

3. The image sensor according to claim 2, wherein: The photodiodes of the second photodiode group include a third photodiode and a fourth photodiode, and The at least one transfer transistor of the second transfer transistor group includes a third transfer transistor connected to the third photodiode and a fourth transfer transistor connected to the fourth photodiode.

4. The image sensor according to claim 3, wherein: The first transfer transistor includes a first transfer gate electrode configured to be input with a first turn-on signal; The second transfer transistor includes a second transfer gate electrode configured to be input with a second turn-on signal, The third transfer transistor includes a third transfer gate electrode configured to be input with the barrier voltage, and The fourth transfer transistor includes a fourth transfer gate electrode configured to be input with the barrier voltage.

5. The image sensor according to claim 1, further comprising: Ground terminal, The ground terminal is configured to provide a ground voltage to the image sensor.

6. The image sensor according to claim 5, wherein: The photodiodes of the second photodiode group include a third photodiode and a fourth photodiode, and The third photodiode is connected to the first drain terminal, and the fourth photodiode is connected to the second drain terminal, wherein: The image sensor is configured to discharge the charge generated from the third photodiode to the first drain terminal in response to applying the power supply voltage to the first drain terminal, The image sensor is configured to discharge the charge generated from the fourth photodiode to the second drain terminal in response to applying the power supply voltage to the second drain terminal, and The ground terminal is between the first drain terminal and the second drain terminal.

7. An image sensor, comprising: A first pixel region and a second pixel region share a single microlens, wherein the first pixel region includes a first photodiode and a second photodiode; a device isolation layer, electrically isolating the first pixel region and the second pixel region from each other; at least one transfer transistor connected to the first pixel region, the at least one transfer transistor comprising a first transfer transistor connected to the first photodiode and a second transfer transistor connected to the second photodiode; as well as At least one drain terminal is connected to the second pixel region and is configured to have a power supply voltage applied thereto.

8. The image sensor according to claim 7, wherein: The second pixel region includes a third photodiode and a fourth photodiode.

9. The image sensor according to claim 8, further comprising: a third transfer transistor connected to the third photodiode; as well as a fourth transfer transistor connected to the fourth photodiode, wherein the third photodiode and the fourth photodiode are connected to each other to form a single photodiode, The third transfer gate electrode of the third transfer transistor and the fourth transfer gate electrode of the fourth transfer transistor are connected to each other to constitute a single transfer gate electrode, and The at least one drain terminal is connected to the single photodiode.

10. The image sensor according to claim 9, wherein: An area of ​​the single photodiode is different from an area of ​​the first photodiode and an area of ​​the second photodiode.

11. The image sensor according to claim 9, further comprising: The floating diffusion region of the substrate, wherein the image sensor is configured to transfer charges generated from the first photodiode and the second photodiode to the floating diffusion region, and The image sensor is configured to discharge charges generated from the single photodiode to the at least one drain terminal.

12. The image sensor according to claim 9, further comprising: The floating diffusion region of the substrate, wherein the single transfer gate electrode is configured to have a barrier voltage applied thereto, and The barrier voltage forms a potential barrier between the single photodiode and the floating diffusion region.

13. The image sensor according to claim 12, further comprising: a ground terminal configured to provide a ground voltage to the image sensor; Wherein, the single transfer gate electrode is between the ground terminal and the at least one drain terminal.

14. The image sensor according to claim 13, wherein: The single photodiode has a first region and a second region, the first region of the single photodiode is on the ground terminal, The second region is on the at least one drain terminal, and The thickness of the first region is different from the thickness of the second region.

15. The image sensor according to claim 14, wherein: A depth of an upper surface of the first region is the same as a depth of an upper surface of the second region, and a depth of a lower surface of the first region is different from a depth of a lower surface of the second region.

16. An image sensor, comprising: A group of common pixels, configured to produce an image; as well as an auto-focus pixel group, configured to provide an auto-focus function, wherein the autofocus pixel group and the common pixel group have substantially the same sensitivity as each other, The auto-focus pixel group includes unit pixels that share a single microlens and each include a single photodiode, a device isolation layer that electrically isolates the unit pixels from each other, and a drain terminal configured to be input with a constant voltage, The autofocus pixel group includes a photodiode, The photodiodes in the auto-focus pixel group include a first photodiode group and a second photodiode group. The drain terminal is connected to the second photodiode group, The first photodiode group is configured to generate charges that migrate from the first photodiode group to a floating diffusion region of a substrate, and The second photodiode group is configured to generate charges that are discharged to the drain terminal.

17. The image sensor according to claim 16, wherein: A conversion gain of charges generated in a photodiode included in the auto-focus pixel group is greater than a conversion gain of charges generated in a photodiode included in the normal pixel group.

18. The image sensor according to claim 16, wherein: A distance between a second metal layer connected to a floating diffusion area of ​​the autofocus pixel group and metal layers surrounding the second metal layer is longer than a distance between a first metal layer connected to a floating diffusion area of ​​the normal pixel group and metal layers surrounding the first metal layer.

19. The image sensor according to claim 16, wherein: A width of the second metal layer connected to the floating diffusion region of the auto-focus pixel group is smaller than a width of the first metal layer connected to the floating diffusion region of the normal pixel group.

20. The image sensor according to claim 16, wherein: The concentration of impurities in the floating diffusion region of the auto-focus pixel group is lower than the concentration of impurities in the floating diffusion region of the normal pixel group.

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