Image sensor and manufacturing method of the same

Abstract

An image sensor according to one embodiment of the present invention comprises a plurality of pixels arranged in a direction parallel to the upper surface of a substrate, wherein the plurality of pixels comprises a pixel array including a plurality of active pixels disposed in an active area and a plurality of dummy pixels disposed in an optical black area where light incident from the outside is blocked, and a logic circuit including a memory that acquires pixel data from the pixel array, wherein the logic circuit generates image data by applying the first compensation data acquired from the dummy pixels to the pixel data acquired from some of the active pixels among the plurality of active pixels, and applying the second compensation data read from the memory to the pixel data acquired from the remaining active pixels among the plurality of active pixels.

Description

Technology Field

[0001] The present invention relates to an image sensor and a method for manufacturing the same. Background Technology

[0003] An image sensor is a semiconductor-based sensor that receives light and generates an electrical signal. It may include a pixel array having multiple pixels and logic circuits for driving the pixel array and generating an image. Each of the multiple pixels includes a photodiode that generates an electric charge in response to light, and an image can be generated using pixel data created based on the charge. Recently, to improve the performance of image sensors, there has been a trend of increasing the number of pixels included in the pixel array and decreasing the size of each pixel. Consequently, it is necessary to adopt methods to minimize the influence of charges generated independently of light in each pixel. The problem to be solved

[0005] One of the objectives of the technical concept of the present invention is to provide an image sensor capable of improving performance by effectively eliminating the influence of charges generated independently of light in a plurality of pixels. means of solving the problem

[0007] An image sensor according to one embodiment of the present invention comprises a plurality of pixels arranged in a direction parallel to the upper surface of a substrate, wherein the plurality of pixels comprises a pixel array including a plurality of active pixels disposed in an active area and a plurality of dummy pixels disposed in an optical black area where light incident from the outside is blocked, and a logic circuit including a memory that acquires pixel data from the pixel array, wherein the logic circuit generates image data by applying the first compensation data acquired from the dummy pixels to the pixel data acquired from some of the active pixels among the plurality of active pixels, and applying the second compensation data read from the memory to the pixel data acquired from the remaining active pixels among the plurality of active pixels.

[0009] A method for manufacturing an image sensor according to an embodiment of the present invention comprises the steps of: manufacturing an image sensor comprising a plurality of active pixels disposed in an active area and a plurality of dummy pixels disposed in an optical black area in which light incident from the outside is blocked; blocking light entering the plurality of active pixels; comparing pixel data obtained from each of the plurality of active pixels with a maximum value and a minimum value of first compensation data obtained from the plurality of dummy pixels; selecting at least some of the active pixels among the plurality of active pixels that output pixel data greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data; and storing the pixel data output by the at least some of the active pixels as second compensation data in a memory. Effects of the invention

[0011] According to one embodiment of the present invention, pixel data obtained under conditions in which light flowing into active pixels of an active region is blocked during the manufacturing stage can be compared with the maximum and minimum values ​​of first compensation data obtained from dummy pixels of an optical black region. Identification information of an active pixel that outputs pixel data greater than the maximum value or smaller than the minimum value, and the pixel data, are stored in memory as second compensation data, and in actual operation, the pixel data output by the active pixel can be compensated using the second compensation data stored in memory. Accordingly, the influence of charges generated in active pixels regardless of light can be minimized, and the performance of the image sensor can be improved.

[0012] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention. Brief explanation of the drawing

[0014] FIG. 1 is a simplified block diagram of an image sensor according to one embodiment of the present invention. FIGS. 2a and 2b are drawings that simply illustrate a pixel circuit of an image sensor according to one embodiment of the present invention. FIGS. 3 and FIGS. 4 are drawings that simply illustrate an image sensor according to an embodiment of the present invention. FIG. 5 is a diagram simply showing a pixel array of an image sensor according to one embodiment of the present invention. Figure 6 is a cross-sectional view showing the cross-section in the II' direction of Figure 5. FIG. 7 is a flowchart provided to explain a method for manufacturing an image sensor according to one embodiment of the present invention. FIGS. 8a and FIGS. 8b are drawings provided to explain a method for manufacturing an image sensor according to an embodiment of the present invention. FIG. 9 is a flowchart provided to explain the operation method of an image sensor according to one embodiment of the present invention. FIGS. 10 and FIGS. 11 are drawings provided to explain a method of operation of an image sensor according to an embodiment of the present invention. FIG. 12 is a flowchart provided to explain the operation method of an image sensor according to one embodiment of the present invention. FIG. 13 is a drawing provided to explain the operation method of an image sensor according to one embodiment of the present invention. Specific details for implementing the invention

[0015] Hereinafter, preferred embodiments of the present invention are described as follows with reference to the attached drawings.

[0017] FIG. 1 is a simplified block diagram of an image sensor according to one embodiment of the present invention.

[0018] Referring to FIG. 1, the image sensor (1) may include a pixel array (10) and a logic circuit (20), etc.

[0019] A pixel array (10) may include a plurality of pixels arranged in an array form along a plurality of rows and a plurality of columns. Each of the plurality of pixels may include at least one photoelectric conversion element that generates a charge in response to light, a pixel circuit that generates a pixel signal corresponding to the charge generated by the photoelectric conversion element, an optical part disposed in a path through which light enters the photoelectric conversion element, etc. The photoelectric conversion element may include a photodiode formed of a semiconductor material, and / or an organic photodiode formed of an organic material, etc.

[0020] For example, the pixel circuit may include a floating diffusion transistor, a transfer transistor, a reset transistor, a driving transistor, and a selection transistor. Depending on the embodiments, the configuration of the plurality of pixels may vary. For example, each of the plurality of pixels may include an organic photodiode containing an organic material, or may be implemented as a digital pixel. When the plurality of pixels are implemented as digital pixels, each of the plurality of pixels may include an analog-to-digital converter for outputting a digital pixel signal.

[0021] The pixel array (10) includes an active region (11) and an optical black region (12), and among the plurality of pixels, active pixels may be placed in the active region (11) and dummy pixels may be placed in the optical black region (12). The optical part of each active pixel may include a micro-lens that refracts light and a color filter that passes light of a specific wavelength band. On the other hand, the optical part of each dummy pixel may include a shielding layer that blocks light from the outside.

[0022] In one embodiment illustrated in FIG. 1, the optical black region (12) is shown surrounding the active region (11), but otherwise, the optical black region (12) may be arranged in various forms around the active region (11). For example, the optical black region (12) may be arranged on one side of the active region (11) in one direction.

[0023] The logic circuit (20) may include circuits for controlling the pixel array (10). For example, the logic circuit (20) may include a memory (21), a row driver (22), a correlated dual sampler (23), an analog-to-digital converter (24), control logic (25), etc. The row driver (22) is connected to the pixel array (10) through a plurality of row lines and can drive the pixel array (10) on a row line basis. For example, the row driver (22) can generate a transmission control signal that controls a transmission transistor of the pixel circuit, a reset control signal that controls a reset transistor, a selection control signal that controls a selection transistor, etc., and input them to the pixel array (10) on a row line basis.

[0024] The correlated dual sampler (23) may include multiple samplers connected to multiple pixels through multiple column lines. The multiple samplers may read pixel signals through the column lines from pixels connected to a row line selected by the row driver (22). The analog-to-digital converter (24) may convert the pixel signal output by the correlated dual sampler (23) into a digital pixel signal to generate pixel data and transmit it to the control logic (25).

[0025] The control logic (25) may include a latch or buffer circuit capable of temporarily storing digitally converted pixel data and an amplifier circuit, and may process pixel data received from an analog-to-digital converter (24). Additionally, the control logic (25) may include a row driver (22), a timing controller for controlling a correlated dual sampler (23) and an analog-to-digital converter (24), and a memory controller for controlling a memory (21).

[0026] Among the pixels, pixels placed at the same position in the row direction may share the same column line. For example, pixels placed at the same position in the vertical direction may be simultaneously selected by the row driver (22) and may output pixel signals through the column lines. In one embodiment, the correlated dual sampler (23) may simultaneously acquire pixel signals from the pixels selected by the row driver (22) through the column lines. The pixel signal may correspond to the difference between the reset voltage and the pixel voltage, and the pixel voltage may be a voltage in which the charge generated in response to light at each of the pixels is reflected in the reset voltage.

[0027] In the operation of acquiring pixel data for generating an image, the logic circuit (20) can acquire pixel data from active pixels in the active area (11) as well as from dummy pixels placed in the optical black area (12). Since the dummy pixels include a shielding layer that blocks light entering from the outside, the pixel data acquired from the dummy pixels may be data corresponding to charges generated by causes other than light, such as dark current. The logic circuit (20) can subtract the pixel data acquired from the dummy pixels as compensation data from the pixel data acquired from the active pixels. Thus, the influence of causes other than light entering from the outside can be minimized, and the quality of the image output by the image sensor (1) can be improved.

[0028] However, depending on the number, size, structure, and process deviation of the pixels arranged in the pixel array (10) of the image sensor (1), the magnitude of the dark current generated in at least some of the active pixels may appear differently. In particular, if an excessively large or excessively small dark current is generated in some of the active pixels, the influence of the dark current may be excessively reflected in the pixel data or the influence of the dark current may not be sufficiently removed from the pixel data by applying the pixel data obtained from the dummy pixels as compensation data.

[0029] In one embodiment of the present invention, to solve the above problem, pixel data generated by dark current in each active pixel can be obtained under a blackout condition in which light entering the active pixels is blocked during the manufacturing of the image sensor (1). Pixel data obtained from the active pixels under the blackout condition can be compared with pixel data obtained from dummy pixels. Pixel data obtained from dummy pixels may have a distribution between a predetermined maximum value and a minimum value, and the address and pixel data of an active pixel that outputs pixel data greater than the maximum value or smaller than the minimum value under the blackout condition can be stored in memory (21). For example, the address and pixel data of the active pixel can be stored in memory (21) in the form of a look-up table.

[0030] When the image sensor (1) starts operation after being shipped, for the active pixel whose address is stored in the memory (21), the pixel data stored in the memory (21) can be applied as compensation data to eliminate the influence of the dark current, instead of the pixel data read from the dummy pixels. Therefore, optimal compensation data can be applied to pixel data obtained from some active pixels where the dark current appears excessively large or small compared to other active pixels due to process deviations, and the performance of the image sensor (1) can be improved.

[0032] FIGS. 2a and 2b are drawings that simply illustrate a pixel circuit of an image sensor according to one embodiment of the present invention.

[0033] First, referring to FIG. 2a, each of the plurality of pixels (PX) includes a photodiode (PD) and a pixel circuit, and the pixel circuit may include a transfer transistor (TX), a reset transistor (RX), a select transistor (SX), and a driving transistor (DX), etc. Additionally, the pixel circuit may include a floating diffusion region (FD) in which charge generated from the photodiode (PD) is accumulated.

[0034] A photodiode (PD) can generate and accumulate charge in response to externally incident light. Depending on the embodiments, the photodiode (PD) may be replaced with a phototransistor, photogate, pinned photodiode, etc. A transfer transistor (TX) can transfer the charge generated in the photodiode (PD) to a floating diffusion region (FD). The floating diffusion region (FD) can store the charge generated in the photodiode (PD). The voltage output by the driving transistor (DX) may vary depending on the amount of charge accumulated in the floating diffusion region (FD).

[0035] The reset transistor (RX) can reset the voltage of the floating diffusion region (FD) by removing the charge accumulated in the floating diffusion region (FD). The drain electrode of the reset transistor (RX) is connected to the floating diffusion region (FD), and the source electrode can be connected to the power supply voltage (VDD). When the reset transistor (RX) is turned on, the power supply voltage (VDD) connected to the source electrode of the reset transistor (RX) is applied to the floating diffusion region (FD), and the charge accumulated in the floating diffusion region (FD) can be removed by the reset transistor (RX).

[0036] The driving transistor (DX) can operate as a source follower buffer amplifier. The driving transistor (DX) can amplify the voltage change of the floating diffusion region (FD) and output it to one of the column lines (COL1, COL2). The select transistor (SX) can select pixels (PX) to be read row by row. When the select transistor (SX) is turned on, the voltage of the driving transistor (DX) can be output to one of the column lines (COL1, COL2). For example, when the select transistor (SX) is turned on, a reset voltage or pixel voltage can be output through the column lines (COL1, COL2).

[0037] In one embodiment illustrated in FIG. 2a, each of the plurality of pixels (PX) may include a photodiode (PD) and a transfer transistor (TX), as well as a reset transistor (RX), a select transistor (SX), and a driving transistor (DX). However, as the number of pixels (PX) included in a single image sensor increases and the area of ​​each pixel (PX) decreases due to limitations in the form factor of the device in which the image sensor is mounted, it may be difficult for each pixel (PX) to include all the elements of the pixel circuit. In this case, two or more adjacent pixels (PX) in the pixel array of the image sensor may share at least some of the elements included in the pixel circuit. This will be explained in more detail below with reference to FIG. 2b.

[0039] Referring to FIG. 2b, two or more adjacent pixels may share at least some of the transistors included in the pixel circuit. In one embodiment illustrated in FIG. 2b, four adjacent pixels may share a floating diffusion region (FD), a reset transistor (RX), driving transistors (DX1, DX2), and a select transistor (SX).

[0040] For example, the first photodiode (PD1) and the first transfer transistor (TX1) of the first pixel can be connected to a floating diffusion region (FD). Similarly, the second to fourth photodiodes (PD2-PD4) of the second to fourth pixels (PX2-PX4) can be connected to a floating diffusion region (FD) through the second to fourth transfer transistors (TX2-TX4). For example, the floating diffusion regions (FD) included in each pixel can be connected to one another using a wiring pattern or the like, so that the first to fourth transfer transistors (TX1-TX4) can be commonly connected to a single floating diffusion region (FD).

[0041] Meanwhile, the pixel circuit may include a reset transistor (RX), first and second driving transistors (DX1, DX2), and a select transistor (SX). The reset transistor (RX) is controlled by a reset control signal (RG), and the select transistor (SX) may be controlled by a select control signal (SEL). For example, each of the four pixels may include one additional transistor in addition to the transfer transistor (TX). Among the four transistors included in the four pixels, two may be connected in parallel to provide the first and second driving transistors (DX1, DX2), one of the remaining two transistors may be provided as the select transistor (SX), and the other may be configured to provide the reset transistor (RX).

[0042] However, the pixel circuit described with reference to FIG. 2b is merely one embodiment and is not necessarily limited to this form. For example, one of the four transistors may be assigned as a driving transistor and one as a selection transistor. Additionally, by connecting the remaining two in series and assigning them as first and second reset transistors, an image sensor capable of controlling the conversion gain of the pixel can be implemented. Alternatively, the pixel circuit may vary depending on the number of transistors included in each pixel.

[0044] FIGS. 3 and FIGS. 4 are drawings that simply illustrate an image sensor according to an embodiment of the present invention.

[0045] Referring to FIGS. 3 and 4, an image sensor (100) according to one embodiment of the present invention may include a first layer (110) and a second layer (120). The first layer (110) may include a pixel array area (111) where a pixel array (PXA) is placed, and a pad area (112) where a plurality of pads connected to the second layer are placed. The pad area (112) may be placed around the pixel array area (111).

[0046] The second layer (120) may include a circuit area (121) and a pad area (122) where a logic circuit (LC) for driving a pixel array is placed. For example, the pad area (112) of the first layer (110) and the pad area (122) of the second layer (120) may be electrically connected to each other through via structures such as through silicon vias (TSVs).

[0047] As previously explained, the logic circuit (LC) placed in the circuit area (121) may include memory in addition to the circuits for driving the pixel array (PXA). Compensation data for compensating for the effects of the dark current may be stored in the memory of the logic circuit (LC). For example, the logic circuit (LC) may use data obtained from dummy pixels placed in the optical black area of ​​the pixel array (PXA) as first compensation data, and data stored in the memory as second compensation data.

[0048] The second compensation data can be stored in memory during the manufacturing process of the image sensor (100). During the manufacturing process of the image sensor (100), an environment in which light is not introduced into the pixel array (PXA) can be established, and pixel data can be obtained from active pixels placed in the active area of ​​the pixel array (PXA). Among the active pixels, active pixels that output pixel data outside the range between the maximum and minimum values ​​of the pixel data output by the dummy pixels in the optical black area can be selected. Address information corresponding to the location of the selected active pixels and the pixel data output by the selected active pixels under the condition in which light is not introduced can be stored in memory in the form of a look-up table. Accordingly, optimal compensation data can be applied to active pixels among the active pixels in which the influence of dark current appears large or small due to process deviations, and the quality of the image output by the image sensor (100) can be improved.

[0050] FIG. 5 is a simplified diagram showing a pixel array of an image sensor according to one embodiment of the present invention, and FIG. 6 is a cross-sectional view showing a cross-section in the II' direction of FIG. 5.

[0051] First, referring to FIG. 5, a pixel array (200) according to one embodiment of the present invention may include a pixel array region (PXA) and a pad region around it. A plurality of pads (205) are disposed in the pad region as previously described, and the plurality of pads (205) may be connected to via structures such as through silicon vias.

[0052] A pixel array region (PXA) may include an active region (201) and an optical black region (202). A plurality of active pixels (203) may be arranged in the active region (201), and a plurality of dummy pixels (204) may be arranged in the optical black region (202). The plurality of active pixels (203) and the plurality of dummy pixels (204) may be arranged along a first direction (X-axis direction) and a second direction (Y-axis direction).

[0053] A plurality of active pixels (203) and a plurality of dummy pixels (204) may have similar structures. Each of the plurality of active pixels (203) may include a photodiode that generates a charge in response to light, a pixel circuit connected to the photodiode that outputs a pixel signal corresponding to the charge, a microlens and a color filter disposed in the path through which light enters the photodiode. Each of the plurality of dummy pixels (204) may include a photodiode, a pixel circuit, and a shielding layer disposed in the path through which light enters the photodiode to block light. According to an embodiment, at least one of the plurality of dummy pixels (204) may not include a photodiode.

[0054] In one embodiment illustrated in FIG. 5, the optical black region (202) may be positioned to surround the active region (201). However, unlike FIG. 5, the optical black region (202) may not be positioned to completely surround the active region (201).

[0055] FIG. 6 is a cross-sectional view showing the cross-section in the II' direction of FIG. 5. Referring to FIG. 6, a plurality of active pixels (APX) may be disposed in the active region, and a plurality of dummy pixels (DPX) may be disposed in the optical black region. Each of the plurality of pixels (APX, DPX) may be separated from one another by a pixel isolation film (207) formed on the substrate (206). Each of the plurality of pixels (APX, DPX) includes a photodiode (PD), and a pixel circuit region may be disposed below the photodiode (PD) in the third "W" direction (Z-axis direction) perpendicular to the upper surface of the substrate (206). For example, the pixel circuit region may include a transmission gate structure (220), a floating diffusion region (231), and other elements necessary for implementing the pixel circuit.

[0056] The floating diffusion region (231) is a region doped with a predetermined impurity and may be a region where charge generated in the photodiode (PD) accumulates. The floating diffusion region (231) may be adjacent to the transmission gate structure (220). The transmission gate structure (220) may be adjacent to the photodiode (PD) formed inside the pixel isolation film (207) in a third direction. The shapes of the floating diffusion region (231) and the transmission gate structure (220) may be varied according to the embodiments. The transmission gate structure (220) may include a transmission gate electrode (221) and a transmission gate insulating layer (222).

[0057] When a first bias voltage is input to the transmission gate structure (220), the charge generated in the photodiode (PD) may not be able to move to the floating diffusion region (231). When the voltage of the transmission gate structure (220) is increased to a second bias voltage higher than the first bias voltage, the charge generated in the photodiode (PD) may move to the floating diffusion region (231). For example, the first bias voltage may be a negative voltage or a ground voltage, and the second bias voltage may be a positive voltage. The absolute value of the first bias voltage may be smaller than the absolute value of the second bias voltage.

[0058] The pixel circuit region may further include a plurality of wiring patterns (240) in addition to the transmission gate structure (220), the floating diffusion region (231), and other elements. The wiring patterns (240) are disposed within the interlayer insulating layer (250) and may include a plurality of contact structures and a plurality of wirings. The interlayer insulating layer (250) includes a plurality of interlayer insulating layers (251-253) sequentially stacked from the substrate (206), and the number of the plurality of interlayer insulating layers (251-253) may vary depending on the embodiments.

[0059] Meanwhile, each of the plurality of active pixels (APX) may include an optical portion disposed on one surface of the substrate (207). In one embodiment, the optical portion may include a horizontal insulating layer (260), a filter separator (270), color filters (271, 272), a flattening layer (273), and microlenses (274). The horizontal insulating layer (260) may include a first horizontal insulating layer (261) and a second horizontal insulating layer (262), and, for example, the first horizontal insulating layer (261) may be formed of a material having a higher dielectric constant than the second horizontal insulating layer (262). The thickness of the first horizontal insulating layer (261) may be smaller than the thickness of the second horizontal insulating layer (262).

[0060] In one embodiment, the filter separator (270) may have a shape extending in a first direction and a second direction similar to the pixel separator (207), and adjacent color filters (271, 272) may be separated from each other in the first direction and the second direction by the filter separator (270). The filter separator (270) and the color filters (271, 272) provide a color filter array, and the micro lenses (274) may provide a micro lens array.

[0061] Light passing through the optical section can be incident on a photodiode (PD) included in each of the plurality of active pixels (APX). In one embodiment illustrated in FIG. 6, each of the plurality of active pixels (APX) is shown as including one photodiode (PD), but depending on the embodiments, at least one of the plurality of active pixels (APX) may include two or more photodiodes (PD). For example, by arranging two or more photodiodes (PD) adjacent to each other in a first direction or a second direction in one active pixel (APX), an autofocus function can be implemented.

[0062] Ideally, the charge generated in each of the multiple active pixels (APX) may consist only of the charge generated by the photodiode (PD) in response to light. However, in reality, charge may be generated in each of the multiple active pixels (APX) by various causes other than light. As such, dark current is generated due to charges generated independently of light, and the quality of the image output by the image sensor may be degraded due to problems such as the occurrence of white spots caused by the dark current.

[0063] To solve the above problem, dummy pixels (DPX) formed in an optical black area may be used. Referring to FIG. 6, the dummy pixels (DPX) may have a structure similar to active pixels (APX). However, unlike active pixels (APX) which include a micro-lens (274) for collecting light and color filters (271, 272) that selectively pass only light of a specific wavelength band, the dummy pixels (DPX) may have a shielding layer (280) and a protective layer (281) formed therein.

[0064] The shielding layer (280) can be formed of a material capable of blocking light entering from the outside. Accordingly, each dummy pixel (DPX) can operate under blackout conditions where external light is blocked, and the pixel data output by each dummy pixel (DPX) may be first compensation data corresponding to dark current. By applying the first compensation data to the pixel data obtained from each active pixel (APX), an image with minimized influence of dark current can be obtained.

[0065] A plurality of dummy pixels (DPX) are placed in an optical black area, and at least some of the plurality of dummy pixels (DPX) can output pixel data of different values. Accordingly, a representative value can be calculated from the pixel data obtained from the plurality of dummy pixels (DPX) and used as the first compensation data.

[0066] However, due to variations in the image sensor manufacturing process, the dark current may appear differently in each active pixel (APX). If the first compensation data is applied as is to an active pixel (APX) that generates a dark current greater than the maximum value of the pixel data obtained from multiple dummy pixels (DPX), the influence of the dark current may not be sufficiently eliminated. Conversely, if the first compensation data is applied as is to an active pixel (APX) that generates a dark current smaller than the minimum value of the pixel data obtained from multiple dummy pixels (DPX), the influence of the dark current may be eliminated more than necessary.

[0067] In one embodiment of the present invention, to prevent the above-mentioned problem from occurring, the dark current of each of the plurality of active pixels (APX) can be measured during the manufacturing stage of the image sensor. Pixel data can be acquired from each of the plurality of active pixels (APX) under conditions where light is not introduced to the plurality of active pixels (APX), and this can be compared with the maximum and minimum values ​​of pixel data acquired from the plurality of dummy pixels (DPX).

[0068] For active pixels (APX) whose pixel data exceeds the maximum value or is smaller than the minimum value, address information indicating their location can be matched with the pixel data output by the corresponding active pixel (APX) and stored in a memory included in the image sensor. The pixel data stored in memory by matching with the address information can be utilized as second compensation data.

[0069] If address information corresponding to the location of a specific pixel exists in memory during an actual readout operation, the logic circuit of the image sensor can read the second compensation data stored in memory, rather than the first compensation data obtained from dummy pixels (DPX) in the optical black area, and apply it to the pixel data of the corresponding pixel. Therefore, the pixel data can be corrected with the second compensation data that accurately reflects the dark current characteristics of the corresponding pixel, and the performance of the image sensor can be improved.

[0071] FIG. 7 is a flowchart provided to explain a method for manufacturing an image sensor according to one embodiment of the present invention.

[0072] Referring to FIG. 7, a method for manufacturing an image sensor according to one embodiment of the present invention may begin with manufacturing an image sensor (S10). As previously described with reference to FIG. 3 and FIG. 4, the image sensor may be manufactured by forming and combining a pixel array and a logic circuit on different layers. However, depending on the embodiments, both the pixel array and the logic circuit may be included in a single layer, or the pixel array and the logic circuit may be distributed and formed on three or more layers.

[0073] When the manufacturing of the image sensor is completed, light entering the pixel array can be blocked (S11). For example, light entering the pixel array can be blocked by placing a shielding member formed of an opaque material capable of blocking light entering from the outside on the pixel array.

[0074] With external light blocked, the logic circuit of the image sensor can acquire pixel data from the active pixels (S12). Since the logic circuit acquires pixel data under conditions where there is no light entering the active pixels, the pixel data acquired in step S12 may be pixel data corresponding to the dark current present in each of the active pixels.

[0075] Meanwhile, the logic circuit of the image sensor can acquire first compensation data in the optical black region of the pixel array (S13). The logic circuit acquires pixel data from dummy pixels placed in the optical black region, and the pixel data acquired from the dummy pixels can be defined as the first compensation data. As previously explained, each of the dummy pixels in the optical black region includes a shielding layer for blocking light, and thus the first compensation data can correspond to the dark current present in each of the dummy pixels.

[0076] Since multiple dummy pixels are placed in the optical black area, the first compensation data obtained by the logic circuit in step S13 can be distributed within a predetermined range. For example, the first compensation data output by a dummy pixel with a relatively large arm current may be larger than the first compensation data output by a dummy pixel with a relatively small arm current. Therefore, the first compensation data can be distributed between a maximum value and a minimum value.

[0077] In the manufacturing process of the image sensor, the processor of the manufacturing equipment connected to the image sensor can compare the pixel data obtained from each of the active pixels in step S12 with the maximum and minimum values ​​of the first compensation data (S14). The manufacturing equipment can determine whether there is an active pixel among the active pixels that outputs pixel data that is greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data (S15).

[0078] If, as a result of the judgment in step S15, there exists an active pixel that outputs pixel data greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data, the manufacturing equipment may store the address of the active pixel and the pixel data output by the active pixel in memory (S16). In the case of an active pixel that outputs pixel data greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data, it may be a pixel in which the dark current appears relatively larger or smaller than other active pixels. Therefore, when the dark current of the active pixel is corrected with the first compensation data obtained from dummy pixels in the optical black area, the influence of the dark current may not be sufficiently removed, or the influence of the dark current may be removed excessively. This will be explained in more detail below with reference to FIGS. 8a and 8b.

[0080] FIGS. 8a and FIGS. 8b are drawings provided to explain a method for manufacturing an image sensor according to an embodiment of the present invention.

[0081] First, FIG. 8a may be a diagram simply illustrating the distribution of first compensation data obtained by a logic circuit from dummy pixels placed in the optical black region of a pixel array. Referring to FIG. 8a, the first compensation data may be distributed between a maximum value (max) and a minimum value (min). At least some of the dummy pixels output the same pixel data, and thus the first compensation data may be distributed as shown in FIG. 8a.

[0082] FIG. 8b may be a diagram simply illustrating pixel data and noise data obtained from each of the different first to third active pixels. Referring to FIG. 8b, the pixel data obtained from each of the different first to third active pixels may include noise data of different sizes. The noise data is data resulting from the dark current of each of the first to third active pixels, and may appear in different sizes in the first to third active pixels due to process deviations, etc.

[0083] For example, the noise data of the first active pixel may be smaller than the maximum value (max) of the first compensation data and larger than the minimum value (min). Therefore, when the first compensation data output by the dummy pixels of the optical black area is applied to the pixel data of the first active pixel, the noise data of the first active pixel can be effectively removed.

[0084] On the other hand, the noise data of the second active pixel may be greater than the maximum value (max) of the first compensation data. Therefore, when compensating for the noise data of the second active pixel using the first compensation data, the noise data may not be sufficiently removed, and the influence of the dark current may remain in the pixel data of the second active pixel, which may degrade the quality of the image output by the image sensor.

[0085] In the case of the third active pixel, the noise data may be smaller than the minimum value (min) of the first compensation data. Therefore, when compensating for the noise data of the third active pixel using the first compensation data, the noise data may be excessively removed, and instead of the influence of the dark current being completely eliminated, some of the valid data among the pixel data may be removed along with it, which may degrade the image quality.

[0086] To solve the above problem, in one embodiment of the present invention, during the manufacturing step of an image sensor, pixel data of each active pixel is acquired under a blackout condition in which light entering the active pixels is blocked, and this can be compared with first compensation data output by dummy pixels. Based on the comparison result, an active pixel that outputs pixel data greater than the maximum value of the first compensation data or smaller than the minimum value can be selected, and the address and pixel data of the selected active pixel can be stored in memory in the form of a look-up table, etc. The address can indicate the location of the selected active pixel. The pixel data stored in memory can be defined as second compensation data.

[0087] Subsequently, during the actual operation of the image sensor, the logic circuit of the image sensor can select compensation data to be applied to the pixel data according to the address of each active pixel from among first compensation data obtained from dummy pixels and second compensation data stored in memory. For example, noise data can be removed by applying the first compensation data to pixel data obtained from some active pixels that do not have addresses in memory. On the other hand, noise data can be removed by applying the second compensation data stored in memory to pixel data obtained from the remaining active pixels that do have addresses in memory. Therefore, noise data can be removed using compensation data optimized by considering the dark current characteristics of each active pixel, and the performance of the image sensor can be improved.

[0089] FIG. 9 is a flowchart provided to explain the operation method of an image sensor according to one embodiment of the present invention.

[0090] Referring to FIG. 9, an operation method of an image sensor according to one embodiment of the present invention may begin with the logic circuit of the image sensor acquiring first compensation data from dummy pixels placed in the optical black area of ​​the pixel array (S20). Additionally, the logic circuit may acquire pixel data from active pixels placed in the active area of ​​the pixel array (S21). The logic circuit may drive the active pixels in row line units and acquire pixel data from active pixels exposed to light for a predetermined exposure time.

[0091] The logic circuit can determine the address of each active pixel that has acquired pixel data (S22) and determine whether the address exists in a look-up table (LUT) stored in memory (S23). As previously explained, the address of each active pixel can correspond to a location where each active pixel is placed in a pixel array and / or active area.

[0092] In the manufacturing stage of an image sensor, pixel data can be obtained from each active pixel under a blackout condition in which light entering the active pixels is blocked, and compared with the maximum and minimum values ​​of the first compensation data obtained from dummy pixels in an optical black area. As a result of the comparison, an active pixel that outputs pixel data greater than the maximum value of the first compensation data or smaller than the minimum value under the blackout condition can be selected, and the address and pixel data of the selected active pixel can be stored in memory in the form of a look-up table. Accordingly, in the look-up table of memory, the address and pixel data of each active pixel that outputs pixel data greater than the maximum value of the first compensation data or smaller than the minimum value under the blackout condition can be recorded as the second compensation data.

[0093] As a result of the judgment in step S23, for an active pixel for which an address exists in the look-up table, the logic circuit of the image sensor can apply second compensation data read from the look-up table to pixel data obtained from the active pixel (S24). On the other hand, for pixel data output by an active pixel for which an address does not exist in the look-up table, the logic circuit can apply first compensation data obtained from dummy pixels in the optical black area (S25). For example, the first compensation data may have a distribution between a maximum value and a minimum value, and the logic circuit can apply representative values ​​such as the average value and median value of the first compensation data to the pixel data.

[0094] By applying the first compensation data or the second compensation data to the pixel data, effective pixel data with minimized influence of dark current can be obtained. The logic circuit of the image sensor can generate image data using the effective pixel data and output it (S26).

[0096] FIGS. 10 and FIGS. 11 are drawings provided to explain a method of operation of an image sensor according to an embodiment of the present invention.

[0097] Referring to FIGS. 10 and 11, an image sensor (300) according to one embodiment of the present invention may include a pixel array (310), a correlated double sampler (320), an analog-to-digital converter (330), etc. In one embodiment illustrated in FIGS. 10 and 11, the pixel array (310) may represent an active region comprising a plurality of active pixels (311, 312), and the pixel array (310) may further include dummy pixels placed around the plurality of active pixels (311, 312). The dummy pixels may be placed in an optical black region where light entering from the outside is blocked.

[0098] Active pixels (311, 312) placed in the active area can be divided into some active pixels (311) and remaining active pixels (312). Some active pixels (311) and remaining active pixels (312) can be distinguished according to the size of the pixel data output under blackout conditions where no light is introduced. For example, the pixel data output by some active pixels (311) under blackout conditions may be less than or equal to the maximum value and greater than or equal to the minimum value of the first compensation data, which is pixel data output by dummy pixels. On the other hand, the pixel data output by remaining active pixels (312) under blackout conditions may be greater than or less than the maximum value of the first compensation data or less than the minimum value.

[0099] Referring to FIGS. 10 and 11, the image sensor (300) can drive the active pixels (311, 312) of the pixel array (310) in a row line unit. While driving each row line, a correlated double sampler (320) samples the pixel signal output by each of the active pixels (311, 312), and an analog-to-digital converter (330) can convert the pixel signal sampled by the correlated double sampler (320) into pixel data (PXD). The pixel data (PXD) output by the analog-to-digital converter (330) may contain noise data due to dark current. To minimize the influence of the noise data, the image sensor (300) may apply compensation data (D1, D2) to the pixel data (PXD).

[0100] As illustrated in FIGS. 10 and 11, a first compensation data (D1) obtained from dummy pixels in an optical black area may be applied to some active pixels (311). As previously explained, each of the some active pixels (311) may output pixel data that is less than or equal to the maximum value and greater than or equal to the minimum value of the first compensation data under blackout conditions. Therefore, the noise data of the pixel data (PXD) output by some active pixels (311) can be sufficiently removed using the first compensation data (D1).

[0101] On the other hand, the second compensation data (D2) read from memory may be applied to the remaining active pixels (312). During the manufacturing process of the image sensor (300), the address and pixel data of each of the remaining active pixels (312) that output pixel data greater than the maximum value of the first compensation data or smaller than the minimum value under blackout conditions may be stored in memory as the second compensation data. The image sensor (300) may select the second compensation data (D2) from memory by referencing the address of each of the remaining active pixels (312) during operation, and apply the second compensation data to the pixel data (PXD) output by each of the remaining active pixels (312). Thus, the noise data included in the pixel data (PXD) output by each of the remaining active pixels (312) can be removed without being too excessive or insufficient.

[0102] Noise data included in the pixel data (PXD) output by each of the active pixels (311, 312) corresponds to dark current and can therefore be affected by the ambient temperature of the image sensor (300). In one embodiment of the present invention, during the manufacturing process of the image sensor (300), the pixel data (PXD) output by each of the active pixels (311, 312) under blackout conditions of various temperatures can be compared with first compensation data, and second compensation data according to temperature can be separately generated and stored in memory. Therefore, noise data included in the pixel data (PXD) can be accurately compensated by taking into account the change in dark current according to temperature.

[0104] FIG. 12 is a flowchart provided to explain the operation method of an image sensor according to one embodiment of the present invention.

[0105] Referring to FIG. 12, an operation method of an image sensor according to one embodiment of the present invention may begin with the logic circuit of the image sensor acquiring first compensation data from dummy pixels placed in the optical black area of ​​the pixel array (S30). Additionally, the logic circuit may acquire pixel data from active pixels placed in the active area of ​​the pixel array (S31). The logic circuit may drive the active pixels in row line units and acquire pixel data from active pixels exposed to light for a predetermined exposure time.

[0106] The logic circuit can determine the address of each active pixel that has acquired pixel data (S32) and detect the operating temperature of the image sensor (S33). In one embodiment described with reference to FIG. 12, the memory can store a plurality of look-up tables that record second compensation data acquired from at least some active pixels under black-out conditions of different temperatures. The logic circuit of the image sensor can determine whether a look-up table matching the temperature detected in step S33 exists in the memory (S34).

[0107] As a result of the judgment in step S34, if there is a look-up table that matches the detected temperature, the logic circuit can select the matching look-up table (S35). On the other hand, if there is no look-up table that matches the detected temperature, the logic circuit can select the look-up table of the temperature closest to the detected temperature (S36). For example, in step S36, the logic circuit may select two or more look-up tables.

[0108] FIG. 13 is a drawing provided to explain a method of operation of an image sensor according to an embodiment of the present invention. Referring to FIG. 13, a memory (400) included in the image sensor may include a plurality of look-up tables. The plurality of look-up tables may be generated by comparing pixel data output by each active pixel under black-out conditions of different temperatures with pixel data output by dummy pixels in an optical black area. Each of the plurality of look-up tables may store the addresses of active pixels (A1-A6, B1-B6, C1-C6) by matching them with pixel data (DA1-DA6, DB1-DB6, DC1-DC6), which is second compensation data. According to an embodiment, at least one of the pixel data (DA1-DA6, DB1-DB6, DC1-DC6) may be matched with two or more of the addresses of active pixels (A1-A6, B1-B6, C1-C6). This may apply to cases where, under blackout conditions, two or more active pixels output the same pixel data.

[0109] For example, the first look-up table may include the addresses (A1-A6) and pixel data (DA1-DA6) of each active pixel that outputs pixel data greater than or less than the maximum value of the first compensation data, which is pixel data output by dummy pixels, under blackout conditions of the first temperature (T1). At least some of the addresses (A1-A6, B1-B6, C1-C6) of each active pixel stored in each of the first to third look-up tables may be different from one another. In other words, as the temperature condition changes, at least some of the active pixels that output pixel data greater than or less than the maximum value of the first compensation data may change. Accordingly, the number of addresses of active pixels may be different in at least some of the first to third look-up tables, and consequently, at least some of the first to third look-up tables may have different capacities.

[0110] For example, if the temperature detected in step S33 matches one of the first to third temperatures (T1-T3), the logic circuit can select one of the first to third look-up tables. For example, among the first to third temperatures (T1-T3), if there is a temperature whose difference from the detected temperature falls within a predetermined range, it can be determined that one of the first to third temperatures (T1-T3) matches the temperature detected in step S33.

[0111] On the other hand, if the temperature detected in step S33 does not match the first to third temperatures (T1-T3), the logic circuit may select the look-up table closest to the detected temperature from among the first to third look-up tables. For example, if the temperature detected in step S33 is greater than the first temperature (T1) and less than the second temperature (T2), the logic circuit may select the first look-up table and the second look-up table.

[0112] Next, the logic circuit can determine whether the address of each active pixel determined in step S32 exists in the look-up table selected in steps S35 and S36 (S37). If an active pixel with an address existing in the look-up table is found in step S35, the second compensation data read from the look-up table can be applied to the pixel data output by the corresponding active pixel (S38). At this time, if a look-up table of a temperature matching the detected temperature is selected as in step S35, the second compensation data corresponding to the address of the active pixel can be found in the selected look-up table and applied to the pixel data. This will be explained in more detail below with reference to FIG. 13.

[0113] On the other hand, if two or more look-up tables of the temperature closest to the detected temperature are selected, as in step S36, the second compensation data can be determined using an interpolation method based on the second compensation data found in the two or more look-up tables. For example, if the logic circuit selects the first look-up table and the second look-up table, the logic circuit can select the second compensation data that matches the address of the active pixel determined in step S32 from the first look-up table and the second look-up table, respectively, and apply an interpolation operation to finally determine the second compensation data.

[0114] Meanwhile, if, as a result of the judgment in step S37, the address of each active pixel determined in step S32 does not exist in the look-up table, the first compensation data obtained from dummy pixels in the optical black area can be applied to the pixel data (S39). The image sensor can generate and output image data using the pixel data to which the first compensation data or the second compensation data has been applied (S40). Accordingly, in one embodiment of the present invention, optimal compensation data can be selected and applied to each active pixel by considering the process deviation of each active pixel and the dark current characteristics according to the ambient temperature of the image sensor, and the performance of the image sensor can be improved.

[0116] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention. Explanation of the symbols

[0118] 1, 100, 300: Image sensor 10, 111, 200, 310: Pixel array 20, 121: Logic circuits

Claims

Claim 1 An image sensor comprising: a pixel array including a plurality of pixels arranged in a direction parallel to the upper surface of a substrate, wherein the plurality of pixels include a plurality of active pixels disposed in an active area and a plurality of dummy pixels disposed in an optical black area where light incident from the outside is blocked; and a logic circuit including a memory for acquiring pixel data from the pixel array; wherein the logic circuit generates image data by applying a first compensation data acquired from the dummy pixels to the pixel data acquired from some of the plurality of active pixels, and applying a second compensation data read from the memory to the pixel data acquired from the remaining active pixels among the plurality of active pixels, wherein the second compensation data is greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data. Claim 2 delete Claim 3 In claim 1, the memory stores the second compensation data by matching it with the location of each of the remaining active pixels, an image sensor. Claim 4 An image sensor according to claim 1, wherein the number of some active pixels is greater than the number of remaining active pixels. Claim 5 An image sensor according to claim 1, wherein each of the active pixels comprises a photodiode that generates a charge in response to light, a color filter disposed above the photodiode, and a microlens disposed above the color filter, and each of the dummy pixels comprises a shielding layer that blocks light, wherein the shielding layer is disposed at the same height as at least one of the color filter and the microlens. Claim 6 In claim 1, the memory stores the second compensation data by matching it with a plurality of different temperatures, and the logic circuit selects one of the second compensation data stored in the memory based on temperature information detected using a temperature sensor, an image sensor. Claim 7 In claim 6, if the temperature information does not match the plurality of temperatures, the logic circuit selects the second compensation data matched with the temperature closest to the temperature information among the plurality of temperatures, an image sensor. Claim 8 In claim 6, if the temperature information does not match the plurality of temperatures, the logic circuit selects a pair of the second compensation data matched to the pair of temperatures closest to the temperature information among the plurality of temperatures, an image sensor. Claim 9 In claim 6, the logic circuit applies data obtained by interpolating a pair of the second compensation data to the pixel data obtained from the remaining active pixels, an image sensor. Claim 10 A method for manufacturing an image sensor comprising: a plurality of active pixels disposed in an active area and a plurality of dummy pixels disposed in an optical black area where light incident from the outside is blocked; a step of blocking light entering the plurality of active pixels; a step of comparing pixel data obtained from each of the plurality of active pixels with a maximum value and a minimum value of first compensation data obtained from the plurality of dummy pixels; a step of selecting at least some of the active pixels among the plurality of active pixels that output pixel data greater than the maximum value of the first compensation data or smaller than the minimum value of the first compensation data; and a step of storing the pixel data output by the at least some of the active pixels as second compensation data in a memory.

Images