image sensor

Abstract

An image sensor includes a pixel array having first pixels and second pixels, each of the first and second pixels including a photodiode, a sampling circuit that detects a reset voltage and a pixel voltage from the first and second pixels and generates an analog signal, an analog-to-digital converter that obtains image data from the analog signal, and a signal processing circuit that generates an image using the image data. Each of the first pixels includes a first-conductivity-type well that separates the photodiode and has an impurity of a first-conductivity type. The photodiode has an impurity of a second-conductivity type that is different from the first-conductivity type. Each of the second pixels includes a second-conductivity-type well that separates the photodiode and has an impurity of the second-conductivity type that is different from the first-conductivity type. The second-conductivity-type well has a higher potential than the first-conductivity-type well.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2019-0140188, filed on November 5, 2019, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Example embodiments of the present invention relate to image sensors. Background Technology

[0004] An image sensor is a semiconductor-based sensor that generates an electrical signal in response to light. An image sensor may include: a pixel array having multiple pixels; logic circuitry configured to drive the pixel array and generate an image; and other components. The multiple pixels may include: a photodiode that generates an electrical charge in response to light; and pixel circuitry that converts the charge generated by the photodiode into an electrical signal. Image sensors are widely used in cameras to obtain still images or video, and can also be used in smartphones, tablet PCs, laptops, televisions, vehicles, and more. Summary of the Invention

[0005] An exemplary embodiment of the present invention provides an image sensor that can improve image quality.

[0006] According to an exemplary embodiment of the present invention, an image sensor includes: a pixel array comprising a first pixel and a second pixel, wherein each pixel of the first pixel and the second pixel includes a microlens, a photodiode spaced apart from each other, and a transfer transistor, and wherein each of the transfer transistors is connected to a corresponding photodiode; a sampling circuit that detects a reset voltage and a pixel voltage from the first pixel and the second pixel, and outputs the difference between the reset voltage and the pixel voltage as an analog signal; an analog-to-digital converter that compares the analog signal with a ramp voltage, converts the comparison result into a digital signal, and outputs the digital signal as image data; and a signal processing circuit that uses the image data to generate an image. Each pixel of the first pixel includes a well of a first conductivity type, the first conductivity type well separating the plurality of photodiodes and having impurities of a first conductivity type. The photodiodes have impurities of a second conductivity type different from the first conductivity type. Each pixel of the second pixel includes a well of a second conductivity type, the second conductivity type well separating the photodiodes and having impurities of a second conductivity type different from the first conductivity type. The potential of the second conductivity type well is higher than the potential of the first conductivity type well.

[0007] According to an exemplary embodiment of the present invention, an image sensor includes: a pixel array including a first pixel and a second pixel; and a controller that receives pixel signals from each of the first pixel and the second pixel and generates an image using the pixel signals. The first pixel includes a first photodiode, a second photodiode, and a first microlens. Both the first photodiode and the second photodiode are disposed below the first microlens. The second pixel includes a third photodiode, a fourth photodiode, and a second microlens. Both the third photodiode and the fourth photodiode are disposed below the second microlens. During a first portion of the exposure time, the sum of the number of electrons gathered in the first photodiode and the number of electrons gathered in the second photodiode increases linearly to a first full-well capacity, the first full-well capacity corresponding to the maximum number of electrons output by the first photodiode and the second photodiode. During a second portion of the exposure time, the sum of the number of electrons gathered in the third photodiode and the number of electrons gathered in the fourth photodiode increases linearly to a second full-well capacity, the second full-well capacity corresponding to the maximum number of electrons output by the third photodiode and the fourth photodiode during the second portion of the exposure time. The second full-well capacity of the second pixel is greater than the first full-well capacity of the first pixel.

[0008] According to an exemplary embodiment of the present invention, an image sensor includes: a pixel array including a first pixel and a second pixel, wherein each of the first pixel and the second pixel includes a microlens, a plurality of photodiodes, a plurality of transfer transistors, and a floating diffusion region, wherein each of the plurality of transfer transistors includes a first electrode connected to a corresponding photodiode of the plurality of photodiodes and a second electrode connected to the floating diffusion region; and a controller that receives a pixel signal from at least one of the first pixel and the second pixel and generates an image using the pixel signal. The photodiode of the first pixel generates a charge in response to light with an illuminance higher than a reference illuminance during an exposure time, and the charge moves to the floating diffusion region via a first path between the plurality of photodiodes and the floating diffusion region. One of the photodiodes of the plurality of photodiodes of the second pixel generates a charge in response to light with an illuminance higher than the reference illuminance during the exposure time, and the charge moves to the other photodiode of the plurality of photodiodes via a second path between the one photodiode and another photodiode of the plurality of photodiodes. Attached Figure Description

[0009] The above and other aspects, features and advantages of the present invention will become more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 This is a block diagram illustrating an image sensor according to an exemplary embodiment of a concept based on the present invention;

[0011] Figure 2 and Figure 3 This is a diagram illustrating an imaging device according to an example embodiment of the concept of the present invention;

[0012] Figure 4 This is a diagram illustrating the operation of an image sensor according to an exemplary embodiment of the concept of the present invention;

[0013] Figure 5 This is a circuit diagram illustrating pixels included in an image sensor according to an exemplary embodiment of the concept of the present invention;

[0014] Figure 6 This is a cross-sectional view showing pixels according to an example embodiment of the concept according to the present invention;

[0015] Figure 7 This is a top view illustrating pixels according to an exemplary embodiment of the concept of the present invention;

[0016] Figure 8 This is a diagram illustrating the potential of an image sensor in optical integration mode according to an exemplary embodiment of the present invention;

[0017] Figure 9 This is a diagram illustrating an example embodiment of the invention based on the amount of light in a pixel;

[0018] Figure 10 This is a top view illustrating pixels according to an exemplary embodiment of the concept of the present invention;

[0019] Figure 11A , Figure 11B and Figure 11C This is a diagram illustrating the potential of an image sensor in optical integration mode according to an exemplary embodiment of the present invention;

[0020] Figure 12 This is a diagram illustrating an example embodiment of the invention based on the amount of light in a pixel;

[0021] Figure 13 This is a circuit diagram illustrating pixels included in an image sensor according to an exemplary embodiment of the concept of the present invention;

[0022] Figure 14A , Figure 14B and Figure 14CThis is a top view illustrating pixels according to an exemplary embodiment of the concept of the present invention;

[0023] Figure 15A , Figure 15B , Figure 15C , Figure 15D and Figure 15E This is a diagram illustrating a portion of the pixel array of an image sensor according to an exemplary embodiment of the concept of the present invention;

[0024] Figure 16A and Figure 16B This is a diagram illustrating a portion of the pixel array of an image sensor according to an exemplary embodiment of the concept of the present invention;

[0025] Figure 17A and Figure 17B This is a diagram illustrating a portion of the pixel array of an image sensor according to an exemplary embodiment of the concept of the present invention; and

[0026] Figure 18 This is a block diagram illustrating a computing device including an image sensor according to an example embodiment of a concept based on the present invention. Detailed Implementation

[0027] In the following description, embodiments of the inventive concept will be described with reference to the accompanying drawings.

[0028] Figure 1 This is a block diagram illustrating an image sensor according to an example embodiment.

[0029] Reference Figure 1 In the example embodiment, the image sensor 100 may include a pixel array 110, a line driver 120, a lead-out circuit 130, a timing controller 140, and a signal processing circuit 150. The line driver 120, lead-out circuit 130, timing controller 140, and signal processing circuit 150 may be included in a controller.

[0030] Image sensor 100 can convert light received from the outside into electrical signals and generate image data. Pixel array 110 included in image sensor 100 may include a plurality of pixels PX, and the plurality of pixels PX may include optoelectronic devices such as photodiodes (PDs) that generate electrical charges in response to light. The plurality of pixels PX may be connected to a plurality of row lines extending along a first direction and a plurality of column lines extending along a second direction different from the first direction. In an example embodiment, each of the plurality of pixels PX may include two or more photodiodes. Each pixel PX may include two or more photodiodes to generate pixel signals corresponding to various colors of light or to provide autofocus functionality.

[0031] Each of the multiple pixels (PX) can include pixel circuitry that generates a pixel signal using the charge generated by photodiodes. For example, the pixel circuitry can include transfer transistors, drive transistors, select transistors, reset transistors, floating diffusion regions, and other components. In each pixel of the multiple pixel PX, the pixel circuitry can detect a reset voltage and a pixel voltage, and can calculate the difference between them to obtain the pixel signal. The pixel voltage can reflect the charge generated by the photodiodes included in each pixel of the multiple pixel PX.

[0032] When multiple pixels (PX) each include two or more photodiodes, each pixel PX may include pixel circuitry for processing the charge generated by each of the two or more photodiodes. Therefore, in an example embodiment, the pixel circuitry may include two or more transfer transistors, each transfer transistor connected to a corresponding photodiode among the two or more photodiodes. In an example embodiment, the pixel circuitry may also include two or more of at least one of a drive transistor, a select transistor, and a reset transistor.

[0033] The row driver 120 can drive the pixel array 110 row by row. The row driver 120 can input (i.e., apply) drive signals to multiple row lines to drive the pixel array 110. For example, the drive signals may include a transfer control signal TG for controlling the transfer transistors of the pixel circuitry, a reset control signal RS for controlling the reset transistors, a selection control signal SEL for controlling the selection transistors, etc. For example, the row driver 120 can drive multiple row lines sequentially, row by row.

[0034] The output 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 132 may include multiple samplers connected to the pixel PX via multiple column lines, and in an example embodiment, the samplers may be configured as correlated dual samplers (CDS). The samplers can detect a reset voltage and a pixel voltage from a pixel PX connected to a selected row line driven by row driver 120. The samplers may output the difference between the reset voltage and the pixel voltage as an analog signal.

[0035] The analog-to-digital converter 133 can convert analog signals into ramp voltage V. RMP By comparing the analog signals, the analog signals can be converted into digital signals based on the comparison results, and the digital signal can be output as the image data LSB. The greater the difference between the reset voltage and the pixel voltage, the larger the value of the image data LSB can be. Therefore, the image data LSB can have a value that increases with the amount of light received by the photodiode.

[0036] Buffer 134 can temporarily store image data LSB received from analog-to-digital converter 133.

[0037] The row driver 120 and the lead-out circuit 130 can be controlled by the timing controller 140. The timing controller 140 can control the timing of the operation of the row driver 120 and the lead-out circuit 130. The row driver 120 can control the operation of the pixel array 110 on a row-by-row basis according to the control of the timing controller 140.

[0038] The signal processing circuit 150 can generate an image using the image data LSB sent from the buffer 134. The signal processing circuit 150 can process the image data LSB and output the processed image data as an image. For example, the signal processing circuit 150 can interpolate the image data LSB corresponding to the pixel signal output from pixel PX and generate interpolated image data.

[0039] Before the signal processing circuit 150 processes the image data LSB, the image sensor 100 can perform a bad pixel correction (BPC) operation using the pixel signal output from the photodiode. The BPC operation will be described later.

[0040] Before the signal processing circuit 150 processes the image data LSB, the image sensor 100 can also use the pixel signals output from the photodiode to calculate parallax and perform an autofocus function. The image sensor 100 can reduce noise or perform other operations to calculate parallax. The autofocus function will be described later.

[0041] Figure 2 and Figure 3 This is a diagram illustrating an imaging device according to an example embodiment.

[0042] Reference Figure 2 The imaging device 10 in the example embodiment may include a first layer 11, a second layer 12 disposed below the first layer 11, and a third layer 13 disposed below the second layer 12. The first layer 11, the second layer 12, and the third layer 13 may be stacked vertically. In the example embodiment, the first layer 11 and the second layer 12 may be stacked at the wafer level, and the third layer 13 may be attached at the chip level to the region below the second layer 12. The first layer 11 to the third layer 13 may be configured as a single semiconductor package.

[0043] The first layer 11 may include a sensing region SA in which a plurality of pixels PX are arranged and a first pad region PA1 disposed around the sensing region SA. The first pad region PA1 may include a plurality of upper pads PAD, and the plurality of upper pads PAD may be connected, for example, to control logic LC and to pads disposed in a second pad region PA2 of the second layer 12 via pathways.

[0044] Each pixel PX may include: a photodiode that generates charge in response to light, and pixel circuitry that processes the charge generated by the photodiode. The pixel circuitry may include multiple transistors for outputting a voltage corresponding to the charge generated by the photodiode.

[0045] Layer 12 may include control logic LC. For example, the control logic LC may include multiple devices such as circuitry for driving pixel circuitry arranged on Layer 11, row drivers, column drivers, timing controllers, and other components. The multiple devices included in the control logic LC can be connected to the pixel circuitry via a first pad area PA1 and a second pad area PA2. The control logic LC can receive reset voltages and pixel voltages from multiple pixels PX and can generate pixel signals.

[0046] In an example embodiment, at least one pixel among a plurality of pixels PX may include a plurality of photodiodes disposed at the same level. The pixel signals generated from the individual photodiodes may have a phase difference, and the control logic LC may provide autofocus functionality based on the phase difference between the pixel signals generated by the plurality of photodiodes included in a single pixel PX.

[0047] The third layer 13, disposed below the second layer 12, may include a memory chip MC, a dummy chip DC, and a protective layer EN encapsulating the memory chip MC and the dummy chip DC. The memory chip MC may be configured as dynamic random access memory (DRAM) or static random access memory (SRAM), and the dummy chip DC may not have a substantial data storage function. The memory chip MC may be electrically connected to at least a portion of the devices included in the control logic LC of the second layer 12 and may store information required to provide autofocus functionality. In an example embodiment, the memory chip MC may be electrically connected to at least a portion of the devices in the control logic LC using bumps such as microbumps.

[0048] Reference Figure 3 The imaging device 20 in the example embodiment may include a first layer 21 and a second layer 22. The first layer 21 may include: a sensing region SA in which a plurality of pixels PX are arranged; control logic LC in which the plurality of pixels PX are arranged; and a first pad region PA1 disposed around the sensing region SA and the control logic LC. A plurality of upper pads PAD may be included in the first pad region PA1, and the plurality of upper pads PAD may be connected, for example, to a memory chip MC disposed on the second layer 22 via pathways. The second layer 22 may include the memory chip MC, a dummy chip DC, and a protective layer EN sealing the memory chip MC and the dummy chip DC.

[0049] Figure 4 This is a diagram illustrating the operation of an image sensor according to an example embodiment.

[0050] Reference Figure 4 In the example embodiment, the pixel array PA of the image sensor may include multiple pixels PX. The multiple pixels PX may be connected to multiple row lines (ROW1 to ROWm) and multiple column lines (COL1 to COLn). The image sensor can drive the multiple pixels PX via the multiple row lines (ROW). For example, the time period required to drive a selected row line (i.e., a selected drive line) and read the reset voltage and pixel voltage from the pixel PX connected to the selected drive line can be defined as the horizontal period. The image sensor can be operated using a rolling shutter method that can drive the multiple row lines (ROW) sequentially, row by row.

[0051] The frame period FT of an image sensor can be defined as the time period required to read the reset voltage and pixel voltage from all pixels included in the pixel array PA. For example, the frame period FT can be equal to or greater than the product of the number of row lines (ROWs) and the horizontal period. The shorter the frame period FT of an image sensor, the more image frames the image sensor can generate in the same time period.

[0052] A photodiode can generate electrons or holes as the primary charge carriers in response to light. In the example embodiment, an example of a photodiode generating electrons as the primary charge carriers in response to light will be described.

[0053] In the following description, reference will be made to Figures 5 to 9 A first example embodiment of 2PD pixels is described. Figure 5 This is a circuit diagram illustrating pixels included in an image sensor according to an example embodiment. A 2PD pixel may refer to a pixel having two photodiodes.

[0054] Reference Figure 5 The pixels included in the image sensor may include two photodiodes PD1 and PD2, as well as pixel circuitry. The pixel circuitry can process the electrons generated by the two photodiodes PD1 and PD2 and can output electrical signals. For example, the pixel circuitry may include two transfer transistors TX1 and TX2, 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.

[0055] The reset transistor RX can be turned on and off by the reset control signal RS, and when the reset transistor RX is turned on, the voltage of the floating diffusion region FD can be reset to the power supply voltage VDD. When the voltage of the floating diffusion region FD is reset, the selection transistor SX can be turned on by the selection control signal SEL, and the reset voltage can be output to the column line COL. The first transfer transistor TX1 and the second transfer transistor TX2 can be turned on and off by the transfer control signals TG1 and TG2, respectively.

[0056] When the first transfer transistor TX1 is turned on after the reset voltage is output to the column line COL, electrons generated by the first photodiode PD1 exposed to light can move to the floating diffusion region FD. The drive transistor DX can be used as a source follower amplifier to amplify the voltage of the floating diffusion region FD, and when the selection transistor SX is turned on by the selection control signal SEL, the first pixel voltage corresponding to the electrons generated by the first photodiode PD1 can be output to the column line COL.

[0057] When the second transfer transistor TX2 is turned on after the first pixel voltage is output to the column line COL, electrons generated by the second photodiode PD2 exposed to light can move to the floating diffusion region FD. The driving transistor DX can be used as a source follower amplifier to amplify the voltage of the floating diffusion region FD, and when the selection transistor SX is turned on by the selection control signal SEL, the second pixel voltage corresponding to the electrons generated by the second photodiode PD2 can be output to the column line COL.

[0058] The reset voltage, the first pixel voltage, and the second pixel voltage can all be detected by a sampling circuit connected to the column line COL. The sampling circuit may include multiple samplers, each sampler having a first input terminal for receiving the reset voltage and a second input terminal for receiving each of the first pixel voltage and the second pixel voltage.

[0059] The sampler can compare the reset voltage received from the first input terminal with the first pixel voltage received from the second input terminal. An analog-to-digital converter (ADC) can be connected to the output terminal of the sampler, and the ADC can output first image data corresponding to the comparison result between the reset voltage and the first pixel voltage.

[0060] The sampler can compare the reset voltage received from the first input terminal with the second pixel voltage received from the second input terminal. An analog-to-digital converter (ADC) can be connected to the output terminal of the sampler, and the ADC can output second image data corresponding to the comparison result between the reset voltage and the second pixel voltage. In an example embodiment, the same ADC can be used to convert the first pixel voltage and the second pixel voltage into first image data and second image data, respectively.

[0061] The signal processing circuit can use the first image data and the second image data to generate an image.

[0062] Figure 6 This is a cross-sectional view showing a pixel (e.g., a 2PD pixel) comprising two photodiodes PD1 and PD2 or PD1' and PD2' according to an example embodiment.

[0063] The pixels PX1 and PX2 of the pixel array 200 may each include two photodiodes PD1 and PD2 and PD1' and PD2', respectively. The first pixel PX1 may include a first photodiode PD1 and a second photodiode PD2, and the second pixel PX2 may include a third photodiode PD1' and a fourth photodiode PD2'.

[0064] In each of pixels PX1 and PX2, a color filter can be placed on two photodiodes. In each of pixels PX1 and PX2, a microlens can be placed on the color filter.

[0065] Two photodiodes PD1 and PD2, as well as PD1' and PD2', can be disposed in a silicon substrate, and deep trench isolation (DTI) can be disposed between the two photodiodes PD1 and PD2 and between the two photodiodes PD1' and PD2'. For example, intra-pixel DTI 32 can be disposed between the two photodiodes PD1 and PD2 and between the two photodiodes PD1' and PD2', while inter-pixel DTI 31 can be disposed between pixels.

[0066] Metallic wiring, multilayer wiring, or wiring layers can be disposed in the circuit region, which is located between the two photodiodes PD1 and PD2, and PD1' and PD2', and the color filter. Lens buffers and planarization layers can be disposed between the microlenses and the color filter.

[0067] Figure 7 This is a top view showing the pixels according to an example embodiment.

[0068] Figure 7 It shows in Figure 6 The XY plane of the pixel in the Z direction is shown. Pixel 300 (e.g., 2PD pixel) may include a first photodiode PD1, a second photodiode PD2, a well R1 of a first conductivity type, a first transfer transistor TX1, and a second transfer transistor TX2.

[0069] A first conductivity type well Rl can be formed by implanting impurity ions of a first conductivity type (e.g., p-type) into a semiconductor substrate. The pixel can have a structure in which a first photodiode PD1 and a second photodiode PD2 share a floating diffusion region FD. For example, the first photodiode PD1 and the second photodiode PD2 can be connected to the floating diffusion region FD via a first transfer transistor TX1 and a second transfer transistor TX2, respectively.

[0070] For example, an ion implantation process can be used to dope each of the first photodiode PD1 and the second photodiode PD2 with an impurity of a second conductivity type (e.g., n-type) in a semiconductor substrate.

[0071] The first transfer transistor TX1 can be connected to the first photodiode PD1. When the first transfer transistor TX1 is turned on, electrons generated by the first photodiode PD1 being exposed to light can accumulate in the floating diffusion region FD.

[0072] The second transfer transistor TX2 can be connected to the second photodiode PD2. When the second transfer transistor TX2 is turned on, electrons generated by the second photodiode PD2 being exposed to light can accumulate in the floating diffusion region FD.

[0073] Figure 8 This is a diagram illustrating the potential level of an image sensor in optical integrated mode according to an example embodiment. Figure 8 The potential of the image sensor in optical integration mode is shown, in which electrons are collected (i.e., accumulated) into photodiodes PD1 and PD2. The first path P1 can refer to the path of electron movement generated by the additional electrons generated by the saturated photodiodes when electrons are collected into photodiodes PD1 and PD2.

[0074] Reference Figure 7 and Figure 8 Photodiodes PD1 and PD2 can be separated from each other by a well R1 of the first conductivity type. The well R1, having a conductivity type opposite to that of photodiodes PD1 and PD2, can provide a potential barrier for the region between photodiodes PD1 and PD2. Therefore, a potential well can be formed in photodiodes PD1 and PD2 through the well R1 of the first conductivity type.

[0075] When the image sensor is working, a first barrier PB1 can be provided in the region between the first conductivity type well R1 and the photodiodes PD1 and PD2 through the potential difference between the potential of the first conductivity type well R1 and the potential of the photodiodes PD1 and PD2.

[0076] In optical integration mode, the well Rl of the first conductivity type can have a second potential V2. In optical integration mode, when the transfer transistor is in the off state, the channel region located below the gate electrode of the transfer transistor can have a first potential V1. The first potential V1 can be higher than the second potential V2. The lower the potential, the higher the energy of the electrons.

[0077] A second barrier PB2 can be provided in the region between the photodiode and the floating diffusion region by means of the potential difference between the potential of the photodiode and the potential of the channel region located below the gate electrode of the transfer transistor. The second barrier PB2 can be lower than the first barrier PB1. A potential well can be formed in the photodiode by means of barriers PB1 and PB2, and electrons can be concentrated in the photodiode by incident light on the photodiode during optical integration mode.

[0078] When light with an illuminance higher than a reference illuminance is incident on a photodiode during optical integration mode, the photodiode can saturate when the number of electrons accumulated therein reaches its full capacity, and electrons exceeding the full capacity can be generated and flow into the floating diffusion region FD. In an example embodiment, the full capacity of the first photodiode PD1 can be determined by a second barrier PB2 between the first photodiode PD1 and the floating diffusion region FD, which is lower than the first barrier PB1. Similarly, the full capacity of the second photodiode PD2 can be determined by a second barrier PB2 between the second photodiode PD2 and the floating diffusion region FD. For ease of description, it is assumed that the first photodiode PD1 is at full capacity, and the first photodiode PD1 at full capacity is referred to as the saturated photodiode PD1. Therefore, electrons additionally generated by the saturated photodiode PD1 can move to the floating diffusion region FD through a first path P1 provided between the saturated photodiode PD1 and the floating diffusion region FD. Electrons moving to the floating diffusion region FD through the first path P1 can be leakage electrons generated when the transfer transistor TX1 connected to the photodiode PD1 is not turned on. Electrons moving to the floating diffusion region FD can be released by a reset operation. Therefore, signal loss may occur.

[0079] Electrons focused into a first photodiode PD1 can generate first image data (e.g., left image data), and electrons focused into a second photodiode PD2 can generate second image data (e.g., right image data). The image sensor can combine the first image data and the second image data and output an image.

[0080] When the first photodiode PD1 and the second photodiode PD2 are off-focus, one of them can receive a greater amount of light than the other. For example, when the first photodiode PD1 receives a greater amount of light, electrons can accumulate in it at a higher rate than in PD2. Therefore, the first photodiode PD1 can saturate earlier than the second photodiode PD2.

[0081] Figure 9 This is a diagram illustrating the output signal based on the amount of light in a pixel according to an example embodiment.

[0082] exist Figure 9 In the diagram, the X-axis represents the product of the effective integration time (EIT) and the illuminance, and the Y-axis represents the signal output by the pixel. Figure 9 The X-axis represents the exposure time. The first signal Sig-a represents the number of electrons gathered in the first photodiode PD1, and the second signal Sig-b represents the number of electrons gathered in the second photodiode PD2. The third signal Sig-c represents the sum of the first signal Sig-a and the second signal Sig-b, that is, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2.

[0083] Reference Figure 8 and Figure 9 In optical integration mode, as the amount of light increases in the first part D1, the number of electrons focused into the first photodiode PD1 and the number of electrons focused into the second photodiode PD2 can increase.

[0084] When the first photodiode PD1 and the second photodiode PD2 are off-focus and the first photodiode PD1 can receive a larger amount of light, the rate of increase in the number of electrons gathered in the first photodiode PD1 can be higher than the rate of increase in the number of electrons gathered in the second photodiode PD2.

[0085] Therefore, the first photodiode PD1 can saturate earlier than the second photodiode PD2. The sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase linearly with a first slope during the first part D1 of the exposure time.

[0086] After the first photodiode PD1 is saturated, since the first photodiode PD1 can remain saturated in the second part D2 of the exposure time in optical integration mode, the number of electrons gathered in the first photodiode PD1 will not increase, while the number of electrons gathered in the second photodiode PD2 can increase.

[0087] The sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase linearly in the second part D2 with a second slope. The second slope can be less than the first slope.

[0088] Therefore, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can be nonlinear throughout the entire portion of the optical integral mode.

[0089] The full-well capacity FWC1 of a pixel can be the maximum number of electrons output by the first photodiode PD1 and the second photodiode PD2 in the first part D1, where the third signal Sig-c has a linear slope with respect to the exposure time. The full-well capacity FWC1 of a pixel can be greater than the full-well capacity of the saturated photodiode among the multiple photodiodes in the pixel.

[0090] In the following description, reference will be made to Figures 10 to 12 A second example embodiment of 2PD pixels is described.

[0091] Figure 10 This is a top view showing the pixels according to an example embodiment.

[0092] Reference Figure 10 Pixel 400 may include a first photodiode PD1 and a second photodiode PD2 disposed along a first direction (e.g., the Y direction).

[0093] and Figure 7 The pixel 300 shown is different. Figure 10 Pixel 400 may also include a second conductivity type well R2 separating the first photodiode PD1 from the second photodiode PD2. The second conductivity type well R2 can be formed by implanting second conductivity type (e.g., n-type) impurity ions into the semiconductor substrate.

[0094] Figure 11A , Figure 11B and Figure 11C This is a diagram illustrating the potential of an image sensor in optical integration mode according to an example embodiment. Figure 11A , Figure 11B and Figure 11C The potential of the image sensor in optical integration mode, where electrons are concentrated into photodiodes PD1 and PD2, is shown. Figure 11A , Figure 11B and Figure 11C The potential can be shown along the line with Figure 10 The potential in the region intercepted by line I-I', which intersects with the second type of conduction well R2. The potential in the region intercepted by line II-II', which intersects with the first type of conduction well R1 between photodiodes PD1 and PD2, can be similar to... Figure 7 The electric potential of that region. As mentioned above... Figure 7 As discussed, due to the first barrier PB1, the additional electrons generated by the first photodiode PD1 do not flow into the second photodiode PD2 through the first conductivity type well R1 between photodiodes PD1 and PD2. Instead, the additional electrons generated by the first photodiode PD1 can flow into the second photodiode PD2 via a second path P2 formed in the second conductivity type well R2. For example, during the period when electrons are concentrated in photodiodes PD1 and PD2, additional electrons generated by the saturated photodiode PD1 can move to the second photodiode PD2 via the second path P2.

[0095] Reference Figure 10 and Figure 11A Photodiodes PD1 and PD2 can be separated from each other by a well R2 of a second conductivity type. In an example embodiment, photodiodes PD1 and PD2 can be further separated from each other by a well R1 of a first conductivity type. The well R2 of the second conductivity type can provide a potential barrier for the region between photodiodes PD1 and PD2. Therefore, a potential well can be formed in photodiodes PD1 and PD2 by the well R2 of the second conductivity type.

[0096] For example, a third barrier PB3 can be provided in the region between the second conductivity type well R2 and photodiodes PD1 and PD2 by means of the difference between the potential of the second conductivity type well R2 and the potential of the photodiode.

[0097] In optical integration mode, the second conductivity type well R2 can have a third potential V3. In an example embodiment, the third potential V3 of the second conductivity type well R2 can vary depending on the doping concentration of the second conductivity type well R2. In an example embodiment, the third potential V3 of the second conductivity type well R2 can vary depending on the width of the second conductivity type well R2 along a second direction (e.g., the X direction).

[0098] When the first transfer transistor TX1 is in the off state in optical integration mode, the channel region located below the gate electrode of the first transfer transistor TX1 can have a first potential V1. A third potential V3 can be higher than the first potential V1. The lower the potential, the higher the energy of the electrons. The same description can be applied to the off state of the second transfer transistor TX2.

[0099] A second barrier PB2 in the region between the first photodiode PD1 and the floating diffusion region FD can be provided as a first potential V1 in the channel region below the gate electrode of the first transfer transistor TX1. A third barrier PB3 (i.e., the difference between the maximum and minimum potentials of the third barrier PB3) can be smaller than the second barrier PB2 (i.e., the difference between the maximum and minimum potentials of the second barrier PB2). The same description can be applied to the second barrier PB2 in the region between the second photodiode PD2 and the floating diffusion region FD. A potential well can be formed in the photodiode by barriers PB2 and PB3, and electrons can be concentrated in the photodiode by light incident on the photodiode during optical integration mode.

[0100] When light with an illuminance higher than the reference illuminance is incident on a photodiode during optical integration mode, an electron capacity greater than that of at least one of photodiodes PD1 and PD2 can be generated. Therefore, the additional electrons generated in one of the saturated photodiodes PD1 and PD2 (e.g., the first photodiode PD1) can move to the other of the photodiodes PD1 and PD2 (e.g., the second photodiode PD2) via a second path P2 between photodiodes PD1 and PD2. Thus, no signal loss occurs.

[0101] Electrons focused into a first photodiode PD1 can generate first image data (e.g., left image data), and electrons focused into a second photodiode PD2 can generate second image data (e.g., right image data). The image sensor can combine the first and second image data and output an image.

[0102] When the first photodiode PD1 and the second photodiode PD2 are off-focus, one of them can receive a greater amount of light than the other. For example, when the first photodiode PD1 receives a greater amount of light, the rate at which electrons accumulate in it can be higher than the rate at which electrons accumulate in it. When the electrons generated by the first photodiode PD1 fill it to a level greater than the third potential V3 (i.e., reaching its full capacity), these electrons can move to the second photodiode PD2 via the second path P2. Therefore, electrons accumulated in the first photodiode PD1 can mix with those accumulated in the second photodiode PD2.

[0103] Reference Figure 11B Due to the mixing of electrons in the first photodiode PD1 and the second photodiode PD2, the second photodiode PD2 is filled with electrons to the third potential V3. (Refer to...) Figure 11CWhen the second photodiode PD2 is filled with electrons to a level greater than the third potential V3, the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 will increase.

[0104] When the image sensor reads the first pixel voltage to generate first image data (e.g., left image data), electrons in the S region are released from the electrons accumulated in the pixel. Therefore, when the second photodiode PD2 is filled with electrons to a level greater than the third potential V3, it indicates that the number of electrons accumulated in the first photodiode PD1 has increased. For example, the first photodiode PD1 can output a first pixel voltage generated from electrons in a quantity greater than the number of electrons it contains at full capacity. The first pixel voltage can be generated from the sum of the number of electrons at full capacity of the first photodiode and the electrons contained in the S region.

[0105] Figure 12 This is a diagram illustrating the output signal based on the amount of light in a pixel according to an example embodiment.

[0106] exist Figure 12 In the diagram, the X-axis represents the product of the effective integration time (EIT) and the illuminance, and the Y-axis represents the signal output by the pixel. Figure 12 The X-axis represents the exposure time. The first signal Sig-a' represents the number of electrons gathered in the first photodiode PD1, and the second signal Sig-b' represents the number of electrons gathered in the second photodiode PD2. The third signal Sig-c' represents the sum of the first signal Sig-a' and the second signal Sig-b', that is, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2.

[0107] In the portion including the first time period D1, the second time period D2, and the third time period D3, the third signal Sig-c' increases linearly with a first slope.

[0108] Reference Figure 11A and Figure 12 During the first time period D1, as the amount of light increases, the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 will increase.

[0109] Since the first photodiode PD1 and the second photodiode PD2 are off-focus, and the first photodiode PD1 can receive a larger amount of light, the rate of increase in the number of electrons gathered in the first photodiode PD1 can be higher than the rate of increase in the number of electrons gathered in the second photodiode PD2.

[0110] Therefore, the first photodiode PD1 can saturate earlier than the second photodiode PD2. The sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase linearly with a first slope during the first time period D1.

[0111] Reference Figure 11B and Figure 12 After the first photodiode PD1 saturates before the second photodiode PD2, the additional electrons generated by the saturated first photodiode PD1 can move to the second photodiode PD2. Therefore, the number of electrons accumulated in the first photodiode PD1 does not increase, while the number of electrons accumulated in the second photodiode PD2 can increase.

[0112] The sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase linearly with a second slope during the second time period D2. The second slope can be the same as the first slope.

[0113] Therefore, during the first time period D1 and the second time period D2, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can be linear.

[0114] Reference Figure 11C and Figure 12 After the second photodiode PD2 also saturates, during the third time period D3 of the optical integration mode, the number of electrons accumulated in the first photodiode PD1 and the second photodiode PD2 can increase. This increase in the number of electrons accumulated in the first photodiode PD1 and the second photodiode PD2 indicates that when the first photodiode PD1 is operated to output its electrons before the second photodiode PD2, the number of electrons accumulated in the second photodiode PD2 may not increase, and the number of electrons accumulated in the first photodiode PD1 may increase. For example, when the image sensor reads the first pixel voltage from the first photodiode PD1 to generate first image data (e.g., left image data), electrons in the S region among the electrons accumulated in the pixel can be released along with the electrons contained in the first photodiode PD1.

[0115] During the third time period D3, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase linearly with a third slope. The third slope can be the same as the first slope.

[0116] Therefore, during the first time period D1, the second time period D2, and the third time period D3, the sum of the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can have the same linear slope with respect to the exposure time.

[0117] After the first photodiode PD1 and the second photodiode PD2 are saturated, the number of electrons gathered in the first photodiode PD1 and the number of electrons gathered in the second photodiode PD2 can increase to the full-well capacity FWC2 of the pixel. Once the number of electrons in the pixel reaches its full-well capacity FWC2, the number of electrons in the pixel will not increase further during the fourth time period D4 of the optical integration mode.

[0118] The full-well capacity FWC2 of a pixel can be the maximum number of electrons output by the pixel during the first time period D1, the second time period D2, and the third time period D3. Within the first time period D1 to the third time period D3, the third signal Sig-c' has the same linear slope relative to the exposure time. Figure 12 In this process, the exposure time may include a first part having a first time period D1 to a third time period D3 and a second part having a fourth time period D4.

[0119] exist Figure 12 The first part of the first to third time intervals D1, D2, and D3, in which the third signal Sig-c' has the same linear slope, can be longer than Figure 9 The third signal Sig-c in the equation has a first part D1 with a linear slope. Therefore, Figure 12 The full-well capacity FWC2 in the middle can be greater than Figure 9 The full-well capacity is FWC1.

[0120] exist Figure 11A In the case of a second type of conductivity trap R2, the third potential V3 can be higher than that of a trap R2. Figure 8 The second potential V2 of the trap R1 of the first conductivity type is shown. Therefore, Figure 11A Pixels in the array can have structures with relatively low charge overflow barrier (COB) levels, while Figure 8 Pixels in the array can have structures with relatively high COB levels. COB can refer to the charge overflow barrier. Figure 11A The COB level in the equation can correspond to the third potential V3 of the third barrier PB3. Figure 8 The COB level in the equation can correspond to the first potential V1 of the second barrier PB2.

[0121] The full-well capacity of a pixel with a relatively low COB level can be higher than that of a pixel with a relatively high COB level.

[0122] Therefore, image sensors can be configured such that all pixels in the pixel array have a relatively low COB level. However, because the pixels are designed to have a reduced size, it can be difficult to adjust their distribution.

[0123] Furthermore, when a pixel with a relatively low COB level is filled to a level greater than COB by electrons generated by the first photodiode PD1, the electrons gathered in the first photodiode PD1 can mix with the electrons gathered in the second photodiode PD2. Therefore, in a low-gain state with an analog gain of 1 (or in a relatively high illumination environment), a pixel with a relatively low COB level cannot be used for autofocus.

[0124] The pixel array of the image sensor in the example embodiment may include both pixels with a relatively high COB level and pixels with a relatively low COB level.

[0125] In the following description, reference will be made to Figure 13 and Figures 14A to 14C An example describing a 4PD pixel. A 4PD pixel can refer to a pixel that has four photodiodes.

[0126] Figure 13 This is a circuit diagram illustrating pixels included in an image sensor according to an example embodiment.

[0127] and Figure 5 The pixels shown are different. Figure 13 The pixel in the image may include four photodiodes PD1 to PD4 and pixel circuitry. The pixel circuitry can process the electrons generated by the four photodiodes PD1 to PD4 and can output electrical signals. For example, the pixel circuitry may include four transfer transistors TX1 to TX4, a reset transistor RX, a drive transistor DX, and a select transistor SX. The first transfer transistor TX1 may be connected to the first photodiode PD1, 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.

[0128] Figure 14A , Figure 14B and Figure 14C This is a top view showing the pixels according to an example embodiment.

[0129] Reference Figure 14APixel 500a may include first photodiodes PD1 to PD4, a first conductivity type well R1, four second conductivity type wells R2 to R5, first transfer transistors TX1 to TX4, and a floating diffusion region FD. First photodiodes PD1 to PD4 may surround the floating diffusion region FD. For example, first photodiodes PD1 and second photodiodes PD2 may be arranged along a first direction (e.g., the Y direction), second photodiodes PD2 and fourth photodiodes PD4 may be arranged along a second direction perpendicular to the first direction (e.g., the Y direction) (e.g., the X direction), third photodiodes PD3 and fourth photodiodes PD4 may be arranged along the first direction, and first photodiodes PD1 and third photodiodes PD3 may be arranged along the second direction.

[0130] The first photodiode PD1 to the fourth photodiode PD4 can all be formed by implanting impurity ions of a second conductivity type (e.g., n-type) into the semiconductor substrate.

[0131] A first conductivity type well R1 can be formed by implanting impurity ions of a first conductivity type (e.g., p-type) into a semiconductor substrate. The pixel can have a structure where first photodiodes PD1 to fourth photodiodes PD4 share a floating diffusion region FD. For example, first photodiodes PD1 to fourth photodiodes PD4 can be connected to the floating diffusion region FD via first transfer transistors TX1 to fourth transfer transistors TX4, respectively.

[0132] Four second-conductivity type wells R2 to R5 can be formed by implanting second-conductivity type (e.g., n-type) impurity ions into a semiconductor substrate. The second-conductivity type well R2 separates the first photodiode PD1 and the second photodiode PD2 from each other. The second-conductivity type well R3 separates the first photodiode PD1 and the third photodiode PD3 from each other. The second-conductivity type well R4 separates the third photodiode PD3 and the fourth photodiode PD4 from each other. The second-conductivity type well R5 separates the fourth photodiode PD4 and the second photodiode PD2 from each other. In an example embodiment, the first-conductivity type well R1 can also separate the first photodiodes PD1 to the fourth photodiode PD4 from each other.

[0133] The first transfer transistor TX1 can be connected to the first photodiode PD1. When the first transfer transistor TX1 is turned on, electrons generated by the first photodiode PD1 being exposed to light can accumulate in the floating diffusion region FD.

[0134] The second transfer transistor TX2 can be connected to the second photodiode PD2. When the second transfer transistor TX2 is turned on, electrons generated by the second photodiode PD2 being exposed to light can accumulate in the floating diffusion region FD.

[0135] The third transfer transistor TX3 can be connected to the third photodiode PD3. When the third transfer transistor TX3 is turned on, electrons generated by the third photodiode PD3 being exposed to light can accumulate in the floating diffusion region FD.

[0136] The fourth transfer transistor TX4 can be connected to the fourth photodiode PD4. When the fourth transfer transistor TX4 is turned on, electrons generated by the fourth photodiode PD4 being exposed to light can accumulate in the floating diffusion region FD.

[0137] and Figure 14A The pixel shown is different from 500a. Figure 14B Pixel 500b may include three second-conductivity type wells R2 to R4. The second-conductivity type well R2 can separate the first photodiode PD1 and the second photodiode PD2 from each other, the second-conductivity type well R3 can separate the first photodiode PD1 and the third photodiode PD3 from each other, and the second-conductivity type well R4 can separate the third photodiode PD3 and the fourth photodiode PD4 from each other.

[0138] and Figure 14A The pixel shown is different from 500a. Figure 14C Pixel 500c may include two second-conductivity type wells R2 and R4. The second-conductivity type well R2 can separate the first photodiode PD1 and the second photodiode PD2 from each other, and the second-conductivity type well R4 can separate the third photodiode PD3 and the fourth photodiode PD4 from each other.

[0139] Figure 15A , Figure 15B , Figure 15C , Figure 15D and Figure 15E This is a diagram illustrating a portion of the pixel array of an image sensor according to an example embodiment.

[0140] Figure 15A , Figure 15B , Figure 15C , Figure 15D and Figure 15EA pixel array comprising 8×8 pixels is shown. The 8×8 pixel array may include multiple pixels R, G, and B. Each of the multiple pixels R, G, and B may include multiple photodiodes. "R" may refer to a red pixel, "G" may refer to a green pixel, and "B" may refer to a blue pixel. Corresponding microlenses may be disposed on each of the pixels R, G, and B. The structure of each pixel in R, G, and B can be compared with a reference... Figures 5 to 14C The structures of the pixels described are basically the same.

[0141] The entire pixel array of an image sensor can be formed by repeatedly arranging pixel arrays, each consisting of 8×8 pixels.

[0142] Reference Figure 15A The pixel array 600a, comprising 8×8 pixels, may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. The pixel array 600a may include a single pixel of the first pixel PX1 with a relatively high COB level and other pixels of the second pixel PX2 with a relatively low COB level.

[0143] Reference Figure 15B A pixel array 600b comprising 8×8 pixels may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. The pixel array comprising 8×8 pixels may include two pixels of the first pixel PX1 with a relatively high COB level and other pixels of the second pixel PX2 with a relatively low COB level.

[0144] Reference Figure 15C A pixel array 600c comprising 8×8 pixels may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. Alternatively, an 8×8 pixel array may include a first pixel PX1 with four pixels and a second pixel PX2 with the remaining pixels.

[0145] Reference Figure 15D A pixel array 600d comprising 8×8 pixels may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. The pixel array comprising 8×8 pixels may include a first pixel PX1 with eight pixels and a second pixel PX2 with the remaining pixels.

[0146] Reference Figure 15EA pixel array 600e comprising 8×8 pixels may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. Alternatively, an 8×8 pixel array may include a first pixel PX1 of sixteen pixels and a second pixel PX2 of sixteen pixels.

[0147] For reference Figures 15A to 15E As described, in the entire pixel array of an image sensor, a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level can be arranged in a regular pattern. However, the exemplary embodiments therein are not limited to this, and in the entire pixel array of the image sensor, the first pixel PX1 with a relatively high COB level and the second pixel PX2 with a relatively low COB level can be arranged in a random pattern.

[0148] The image sensor in the example embodiment may include a first pixel PX1 with a relatively high COB level and a second pixel PX2 with a relatively low COB level. In a high-gain state with an analog gain of twice or higher (or in a relatively low-illuminance environment), both the first pixel PX1 with the relatively high COB level and the second pixel PX2 with the relatively low COB level can be used for autofocus and for generating an image.

[0149] For example, when the COB level of the second pixel PX2, which has a relatively low COB level, is 50% or higher of the overall pixel potential, the second pixel PX2 can be used for autofocus with an analog gain of two times or higher. When the COB level of the second pixel PX2, which has a relatively low COB level, is 25% or higher of the overall pixel potential, the second pixel PX2 can be used for autofocus with an analog gain of four times or higher.

[0150] In a low-gain state with a simulated gain of 1x (or in a relatively high illumination environment), the second pixel PX2, with a relatively low COB level, cannot be used for autofocus but can be used to generate an image. The first pixel PX1, with a relatively high COB level, can be used for autofocus. To generate an image using the first pixel PX1 with a relatively high COB level, a BPC operation may be required. For example, in a BPC operation, a threshold pixel value or adjacent pixel values ​​can be used to detect bad pixels (e.g., hot pixels, dead pixels, stuck pixels). By filtering and correcting the detected bad pixels, they can be restored to normal pixels.

[0151] Therefore, in a low-gain state with a simulated gain of 1x (or in a relatively high illumination environment), the more first pixels (PX1) with relatively high COB levels across the entire pixel array of the image sensor, the greater the improvement in autofocus. Furthermore, the more second pixels (PX2) with relatively low COB levels across the entire pixel array of the image sensor, the greater the improvement in image quality.

[0152] In example embodiments, the ratio of the number of pixels with relatively high COB levels to the number of pixels with relatively low COB levels in the entire pixel array of the image sensor may be 1:3 or less, but example embodiments are not limited thereto. For example, in example embodiments, the ratio of the number of pixels with relatively high COB levels to the number of pixels with relatively low COB levels may be greater than 0% and less than or equal to 25%.

[0153] In an example embodiment, the image sensor can only be used in low-light environments when the ratio of the number of pixels with relatively high COB levels to the number of pixels with relatively low COB levels in the entire pixel array of the image sensor is 95% or higher.

[0154] In an example embodiment, two photodiodes may be positioned below a single microlens for each pixel in the pixel array of the image sensor. The image sensor can use the output difference between the two photodiodes to perform an autofocus function.

[0155] Unlike the configurations described above, an image sensor may include a pixel specifically designed to sense phase differences to perform autofocus. In this case, a thin metal film can be used to mask half of the pixel, and the paired phase differences sensed from the pixels to its left and right (also masked by the metal film) can be used. However, adjacent pixels may receive interference from signals reflected by the metal film of one of the pixels, potentially introducing noise.

[0156] In the example embodiment, the image sensor can use the output difference between two photodiodes to perform autofocus without crosstalk.

[0157] Furthermore, autofocus can be achieved by placing two photodiodes below a single microlens in only some pixels. In this case, the horizontal and vertical lengths of the microlens in each pixel may differ from one another. Therefore, the image sensor can have optically different shapes, and adjacent pixels may receive interference from signals reflected from the microlens of one of the pixels, potentially causing noise.

[0158] However, since the image sensor in the example embodiment can perform autofocus using differences in doping concentration and doping structure between the wells that separate the photodiodes, no crosstalk occurs.

[0159] Therefore, the image sensor in the example embodiment can have an improved signal-to-noise ratio (SNR) in high-light environments.

[0160] Figure 16A and Figure 16B This is a diagram illustrating a portion of the pixel array of an image sensor according to an example embodiment.

[0161] Reference Figure 16A In the pixel array 700a of the image sensor in the example embodiment, two or more pixels that share one of the multiple color filters CF1 to CF4 may share at least one floating diffusion region.

[0162] For example, 2×2 blue pixels M, S, L, and M (i.e., the first group of blue pixels) can form a single group in the first color filter CF1. 2×2 green pixels M, S, L, and M (i.e., the second group of green pixels) can form a single group in the second color filter CF2. 2×2 green pixels M, S, L, and M (i.e., the third group of green pixels) can form a single group in the third color filter CF3. 2×2 red pixels M, S, L, and M (i.e., the fourth group of red pixels) can form a single group in the fourth color filter CF4. In the example embodiment, each of the first to fourth groups of pixels may include four pixels, namely, a first pixel PX1, a second pixel PX2, a third pixel PX3, and a fourth pixel PX4. In each of the four groups of pixels, the four pixels may have the same configuration.

[0163] exist Figure 16A In this context, "M" can refer to either the first pixel PX1 or the fourth pixel PX4, "S" can refer to the second pixel PX2, and "L" can refer to the third pixel PX3. L, M, and S can be distinguished based on the length of time the photodiodes included in the pixel are exposed to light. For example, "L" can be a pixel containing a photodiode that generates a long-exposure image signal. "M" can be a pixel containing a photodiode that generates an intermediate-exposure image signal. "S" can be a pixel containing a photodiode that generates a short-exposure image signal.

[0164] An image sensor can generate a single image using pixel signals obtained from different exposure times. In an example embodiment, a single image can be generated using pixel signals obtained from the same exposure time.

[0165] Each of pixels PX1 through PX4 may include two photodiodes. In this case, at least one of the 2×2 pixels PX1 through PX4 sharing a single color filter can have a relatively high COB level. Pixels with a relatively high COB level may include a separate floating diffusion area. Other pixels may share at least one floating diffusion area.

[0166] As described above, pixels with relatively high COB levels can be used to generate images in relatively low illumination environments, while in relatively high illumination environments, BPC operations may need to be performed to generate images using pixels with relatively high COB levels. Therefore, in the 2×2 pixels PX1 to PX4 sharing a single color filter, pixels including photodiodes capable of generating short-exposure image signals can have relatively high COB levels.

[0167] For example, when the second pixel PX2 has a relatively high COB level, the second pixel PX2 may include a first floating diffusion area FD1, while the first pixel PX1, the third pixel PX3, and the fourth pixel PX4 may share a second floating diffusion area FD2. The second pixel PX2 can output a reset voltage and a pixel voltage OUT2 through the second column line COL2. The first pixel PX1, the third pixel PX3, and the fourth pixel PX4 can output the average value of the reset voltage and the average value of the pixel voltage OUT1 through the first column line COL1. Similarly, voltage signals OUT3 and OUT4 can be output through column lines COL3 and COL4, respectively.

[0168] and Figure 16A The examples shown are different. Figure 16B An example of a pixel array 700b with at least one pixel in a 4×4 pixel array has a relatively high COB level. For example, at least one pixel included in the green filter can have a relatively high COB level. This is because, among the 4×4 pixels, the number of pixels included in the green filter can be the highest, making the pixels advantageous for BPC operations.

[0169] For example, when pixels PX1 to PX4 sharing the first color filter CF1 do not include pixels with a relatively high COB level, pixels PX1 to PX4 can share a single floating diffusion area FD. Among pixels PX1 to PX4 sharing the second color filter CF2, when the second pixel PX2 has a relatively high COB level, the second pixel PX2 can include the first floating diffusion area FD1, while the first pixel PX1, the third pixel PX3, and the fourth pixel PX4 can share the second floating diffusion area FD2.

[0170] Figure 17A and Figure 17BThis is a diagram illustrating a portion of the pixel array of an image sensor according to an example embodiment.

[0171] Reference Figure 17A In the pixel array 800a of the image sensor in the example embodiment, two or more pixels that share one of the multiple color filters CF1 to CF4 may share at least one floating diffusion region.

[0172] For example, 3×3 blue pixels (L, S, M, ..., L, S, M) can form a single group in the first color filter CF1. 3×3 green pixels (L, S, M, ..., L, S, M) can form a single group in the second color filter CF2. 3×3 green pixels (L, S, M, ..., L, S, M) can form a single group in the third color filter CF3. 3×3 red pixels (L, S, M, ..., L, S, M) can form a single group in the fourth color filter CF4. The 3×3 blue pixels in the first color filter CF1 can be referred to as the first group of blue pixels. The 3×3 green pixels in the second color filter CF2 can be referred to as the second group of green pixels. The 3×3 green pixels in the third color filter CF3 can be referred to as the third group of green pixels. The 3×3 red pixels in the fourth color filter CF4 can be referred to as the fourth group of red pixels. In the example embodiment, each of the first to fourth groups of pixels may include nine pixels, namely, a first pixel PX1, a second pixel PX2, a third pixel PX3, a fourth pixel PX4, a fifth pixel PX5, a sixth pixel PX6, a seventh pixel PX7, an eighth pixel PX8, and a ninth pixel PX9. Within each of the four groups of pixels, the nine pixels may have the same configuration.

[0173] exist Figure 17A In this context, "L" can refer to one of the first pixel PX1, the sixth pixel PX6, and the eighth pixel PX8; "S" can refer to the second pixel PX2, the fourth pixel PX4, and the ninth pixel PX9; and "M" can refer to the third pixel PX3, the fifth pixel PX5, and the seventh pixel PX7. L, M, and S can be distinguished based on the length of time the photodiodes included in the pixel are exposed to light. For example, L can be a pixel containing a photodiode that generates a long-exposure image signal. M can be a pixel containing a photodiode that generates an intermediate-exposure image signal. S can be a pixel containing a photodiode that generates a short-exposure image signal.

[0174] Each of the pixels PX1 through PX9 may include two photodiodes. In this case, at least one of the 3×3 pixels PX1 through PX9 sharing a single color filter can have a relatively high COB level. Pixels with a relatively high COB level can have a separate floating diffusion area. Other pixels can share at least one floating diffusion area.

[0175] As described above, pixels with relatively high COB levels can be used to generate images in relatively low illumination environments, while in relatively high illumination environments, BPC operations may need to be performed to generate images using pixels with high COB levels. Therefore, in the 3×3 pixel PX1 to PX9 sharing a single color filter, pixels including photodiodes capable of generating short-exposure image signals can have relatively high COB levels.

[0176] For example, when the fourth pixel PX4 has a relatively high COB level, the fourth pixel PX4 may include a second floating diffusion area FD2, while the first pixel PX1, the second pixel PX2, and the third pixel PX3 may share the first floating diffusion area FD1. The fifth pixel PX5 and the sixth pixel PX6 may share the third floating diffusion area FD3, while the seventh pixel PX7, the eighth pixel PX8, and the ninth pixel PX9 may share the fourth floating diffusion area FD4.

[0177] The fourth pixel PX4 can output the reset voltage and pixel voltage OUT2 through the second column line COL2. The first pixel PX1, the second pixel PX2, and the third pixel PX3 can output the average value of the reset voltage and the average value of the pixel voltage OUT1 through the first column line COL1. The fifth pixel PX5 and the sixth pixel PX6 can output the average value of the reset voltage and the average value of the pixel voltage OUT2 through the second column line COL2, and the seventh pixel PX7, the eighth pixel PX8, and the ninth pixel PX9 can output the average value of the reset voltage and the average value of the pixel voltage OUT3 through the third column line COL3. Similarly, voltage signals OUT4 to OUT6 can be output through column lines COL4 to COL6 respectively.

[0178] and Figure 17A The difference lies in Figure 17B In the 800b pixel array, at least one pixel in a 6×6 pixel array can have a relatively high COB level. Ideally, at least one pixel included in the green filter can have a relatively high COB level. This is because, within a 6×6 pixel array, the number of pixels included in the green filter can be the highest, making the pixel advantageous for BPC.

[0179] In the example embodiments, RGGB (red, green, green, and blue) has been described, but the example embodiments are not limited thereto. Example embodiments may include RYYB (red, yellow, yellow, and blue) or RGBW (red, green, blue, and white). Furthermore, the total number of pixels included in the pixel array is not limited to this. Figure 17A and Figure 17BThe number of pixels shown. Furthermore, in the case of RGBW (red, green, blue, and white), at least one pixel included in the green filter CF2 can have a relatively high COB level.

[0180] Figure 18 This is a block diagram illustrating a computing device including an image sensor according to an example embodiment.

[0181] Figure 18 The computing device 1000 may include a display 1010, a sensor unit 1020, a memory 1030, a processor 1040, a bus 1060, input and output devices 1070, and other components. The computing device 1000 may also include power devices, input and output devices, and other components. Figure 18 Among the components shown, port 1050 can be provided to allow computing device 1000 to communicate with video cards, sound cards, memory cards, USB devices, and other components. Computing device 1000 may include general-purpose desktop computers and laptop computers, as well as smartphones, desktop PCs, smart wearable devices, etc.

[0182] The processor 1040 can perform specific operations or process command words, tasks, etc. The processor 1040 can be implemented as a central processing unit (CPU), microprocessor unit (MCU), system on chip (SoC), etc., and can communicate with the display 1010, sensor unit 1020 and memory 1030 via bus 1060, and can also communicate with other devices connected to port 1050.

[0183] The memory 1030 may be a storage medium for storing data, multimedia data, etc., required for the operation of the computing device 1000. The memory 1030 may include volatile memory such as random access memory (RAM) or non-volatile memory such as flash memory. The memory 1030 may include at least one of a solid-state drive (SSD), a hard disk drive (HDD), and an optical disk drive (ODD) as a storage device. The input and output devices 1070 may include input devices such as a keyboard, mouse, and touchscreen, and output devices such as a display and an audio output unit.

[0184] Sensor unit 1020 may include various sensors such as image sensors, GPS sensors, and light sensors. The image sensor included in sensor unit 1020 can be used in reference... Figures 1 to 17B The forms described in the foregoing example embodiments are used in computer device 1000.

[0185] According to the foregoing example embodiments, the pixel array of the image sensor may include pixels with relatively high COB levels and pixels with relatively low COB levels. Therefore, the full-well capacity of each pixel can be increased.

[0186] Furthermore, as the full-well capacity of pixels increases, the image quality can be improved.

[0187] In addition, it can improve SNR in high-illuminance environments.

[0188] Although exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and changes 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 pixel array, comprising a plurality of first pixels and a plurality of second pixels, Each of the plurality of first pixels and the plurality of second pixels includes: a microlens, a plurality of photodiodes spaced apart from each other in at least one of a first direction and a second direction perpendicular to the first direction, and a plurality of transfer transistors. Each of the plurality of transfer transistors is connected to a corresponding photodiode among the plurality of photodiodes; A sampling circuit is configured to detect a reset voltage and a pixel voltage from the plurality of first pixels and the plurality of second pixels, and output the difference between the reset voltage and the pixel voltage as an analog signal; An analog-to-digital converter configured to compare the analog signal with a ramp voltage to convert the result of the comparison into a digital signal and output the digital signal as image data; and A signal processing circuit, configured to generate an image using the image data, Each of the plurality of first pixels includes a well of a first conductivity type, the first conductivity type well separating the plurality of photodiodes and having impurities of the first conductivity type. The plurality of photodiodes have impurities of a second conductivity type that is different from the first conductivity type. Each of the plurality of second pixels includes a well of a second conductivity type, the second conductivity type well separating the plurality of photodiodes and having impurities of the second conductivity type different from the first conductivity type. Wherein, the potential of the well of the second conductivity type is higher than the potential of the well of the first conductivity type, and Wherein, the full well capacity of each of the plurality of second pixels is greater than the full well capacity of each of the plurality of first pixels.

2. The image sensor according to claim 1, in, The image sensor is configured to perform autofocus using each of the plurality of first pixels and the plurality of second pixels in a low-light environment.

3. The image sensor according to claim 2, in, The image sensor is also configured to generate an image using each of the plurality of first pixels and the plurality of second pixels in the low-light environment.

4. The image sensor according to claim 1, in, The image sensor is configured to generate an image using each of the plurality of second pixels in a high-light environment, and to perform an autofocus function using each of the plurality of first pixels.

5. The image sensor according to claim 4, in, The image sensor is also configured to perform a bad pixel correction operation in the high-light environment to generate an image using each of the plurality of first pixels.

6. The image sensor according to claim 1, in, The ratio of the number of the first pixel to the number of the second pixel is 1:3 or less.

7. The image sensor according to claim 1, in, When the first transfer transistor among the plurality of transfer transistors is in the off state, the potential of the channel region disposed below the gate electrode of the first transfer transistor is lower than the potential of the well of the second conductivity type.

8. The image sensor according to claim 1, in, The potential of the second type of conductivity well varies depending on the doping concentration of the second type of conductivity impurity in the second type of conductivity well.

9. The image sensor according to claim 1, in, When the plurality of photodiodes are spaced apart from each other in the first direction, the potential of the second conductivity type well varies according to the width of the second conductivity type well along the second direction.

10. The image sensor according to claim 1, in, The plurality of photodiodes respond to light to generate electrons as the primary charge carriers, and the lower the potential of the trap of the first conductivity type, the higher the energy of the electrons.

11. An image sensor, comprising: A pixel array, the pixel array comprising a first pixel and a second pixel; as well as A controller configured to receive pixel signals from each of the first and second pixels and use the pixel signals to generate an image. The first pixel includes a first photodiode, a second photodiode, and a first microlens. Both the first photodiode and the second photodiode are positioned below the first microlens. The second pixel includes a third photodiode, a fourth photodiode, and a second microlens. Both the third photodiode and the fourth photodiode are positioned below the second microlens. During the first portion of the exposure time, the sum of the number of electrons gathered in the first photodiode and the number of electrons gathered in the second photodiode increases linearly to a first full-well capacity, which corresponds to the maximum number of electrons output by the first and second photodiodes. During the second time portion of the exposure time, the sum of the number of electrons gathered in the third photodiode and the number of electrons gathered in the fourth photodiode increases linearly to a second full-well capacity, which corresponds to the maximum number of electrons output by the third and fourth photodiodes during the second time portion. Wherein, the second full-well capacity of the second pixel is greater than the first full-well capacity of the first pixel.

12. The image sensor according to claim 11, in, During the first time portion of the exposure time, the number of electrons gathered in the first photodiode and the number of electrons gathered in the second photodiode increase, and Wherein, after the first time portion, the number of electrons gathered in at least one of the first and second photodiodes does not increase.

13. The image sensor according to claim 11, in, During the first time period of the second time segment, the number of electrons gathered in the third photodiode and the number of electrons gathered in the fourth photodiode increase. Specifically, during the second time period following the first time period in the second time segment, the number of electrons gathered in the third photodiode does not increase, while the number of electrons gathered in the fourth photodiode increases. During the third time period following the second time period in the second time segment, the number of electrons gathered in the third photodiode and the fourth photodiode increases.

14. The image sensor according to claim 13, in, Once the third photodiode is saturated, during the second time period of the second time portion, electrons gathered in the third photodiode and electrons gathered in the fourth photodiode mix.

15. The image sensor according to claim 13, in, When the image sensor reads the pixel voltage from the third photodiode, the electrons added during the third time period in the second time portion, as well as the electrons contained in the saturated third photodiode, are released.

16. An image sensor, comprising: A pixel array, comprising a first pixel and a second pixel, wherein each pixel in the first pixel and the second pixel includes a microlens, multiple photodiodes, multiple transfer transistors, and a floating diffusion region. Each of the plurality of transfer transistors includes a first electrode connected to a corresponding photodiode among the plurality of photodiodes and a second electrode connected to the floating diffusion region; and A controller configured to receive pixel signals from at least one of the first pixel and the second pixel, and to generate an image using the pixel signals. In this embodiment, the plurality of photodiodes of the first pixel generate charges in response to light with an illuminance higher than a reference illuminance during the exposure time. These charges then move to the floating diffusion region via a first path between the plurality of photodiodes and the floating diffusion region. Wherein, during the exposure time, the first photodiode of the plurality of photodiodes of the second pixel generates a charge in response to light with an illuminance higher than the reference illuminance. This charge moves to the second photodiode through a second path between the first photodiode and the second photodiode. The full-well capacity of the second pixel is greater than that of the first pixel.

17. The image sensor according to claim 16, in, The first pixel includes a first conductivity type trap that separates the plurality of photodiodes. The second pixel includes a second type of well that separates the plurality of photodiodes, and The potential of the second type of well is higher than that of the first type of well.

18. The image sensor according to claim 17, in, When the first transfer transistor among the plurality of transfer transistors is in the off state, the potential of the channel region disposed below the gate electrode of the first transfer transistor is lower than the potential of the well of the second conductivity type.

19. The image sensor according to claim 17, in, When the first transfer transistor among the plurality of transfer transistors is in the off state, the potential of the channel region disposed below the gate electrode of the first transfer transistor is higher than the potential of the well of the first conductivity type.

Images