Image sensor

Abstract

An image sensor according to an embodiment of the present invention comprises: a pixel array including a plurality of photodiodes arranged along a direction parallel to the upper surface of a substrate, a pixel separator extending from the upper surface of the substrate to the lower surface of the substrate in a direction perpendicular to the upper surface of the substrate and disposed between the plurality of photodiodes, and pixel circuits disposed below each of the plurality of photodiodes; and a logic circuit for acquiring a pixel signal from the pixel circuits, wherein the pixel array comprises pixel groups each including two or more photodiodes arranged in an N×N (N is a natural number greater than or equal to 2) matrix structure among the plurality of photodiodes, at least one color filter disposed on the substrate, and at least one microlens, wherein the at least one color filter included in each of the pixel groups has one color, and the pixel separator comprises a first pixel separator disposed between the pixel groups and comprising silicon oxide and polysilicon; and a second pixel separator extending between the two or more photodiodes in each of the pixel groups in a first direction parallel to the upper surface of the substrate and intersecting each other and comprising silicon oxide.

Description

Technology Field

[0001] The present invention relates to an image sensor. Background Technology

[0003] An image sensor is a semiconductor-based sensor that receives light and generates an electrical signal, and may include a pixel array having multiple pixels and a logic circuit for driving the pixel array and generating an image. The pixel array constituting the image sensor may include a photoelectric conversion element for each pixel. When the photoelectric conversion element generates an electrical signal that varies according to the amount of incident light, the logic circuit can process the electrical signal to generate an image.

[0004] Deep Trench Isolation (DTI) layers can be formed between pixels to separate them. Due to the demand for miniaturization of image sensors, the size of pixels is trending downward. As the pixel size decreases, the area occupied by the DTI layer increases, and the impact of light absorbed by the DTI layer on the performance of the image sensor increases. The problem to be solved

[0006] One of the objectives of the technical concept of the present invention is to provide an image sensor with improved sensitivity. means of solving the problem

[0008] An image sensor according to an embodiment of the present invention comprises: a pixel array including a plurality of photodiodes arranged along a direction parallel to the upper surface of a substrate, a pixel separator extending from the upper surface of the substrate to the lower surface of the substrate in a direction perpendicular to the upper surface of the substrate and disposed between the plurality of photodiodes, and pixel circuits disposed below each of the plurality of photodiodes; and a logic circuit for acquiring a pixel signal from the pixel circuits, wherein the pixel array comprises pixel groups each including two or more photodiodes arranged in an N×N (N is a natural number greater than or equal to 2) matrix structure among the plurality of photodiodes, at least one color filter disposed on the substrate, and at least one microlens, wherein the at least one color filter included in each of the pixel groups has one color, and the pixel separator comprises a first pixel separator disposed between the pixel groups and comprising silicon oxide and polysilicon; and a second pixel separator extending between the two or more photodiodes in each of the pixel groups in a first direction parallel to the upper surface of the substrate and intersecting each other and comprising silicon oxide.

[0009] An image sensor according to an embodiment of the present invention comprises a plurality of pixels arranged along a direction parallel to the upper surface of a substrate, and a pixel separator extending from the upper surface of the substrate to the lower surface between the plurality of pixels, wherein each of the plurality of pixels comprises at least one photodiode and a pixel circuit below the at least one photodiode, and a pixel array; and a logic circuit for acquiring a pixel signal from the plurality of pixels, wherein the pixel separator comprises a first pixel separator comprising polysilicon having a first transmittance, disposed between pixels among the plurality of pixels that are adjacent to each other and configured to detect light of different colors; and a second pixel separator disposed between pixels among the plurality of pixels that are adjacent to each other and configured to detect light of the same color, having a second transmittance higher than the first transmittance, and extending in a first direction and a second direction parallel to the upper surface of the substrate and intersecting each other.

[0010] According to an embodiment of the present invention, the pixel array comprises a plurality of pixels arranged along a direction parallel to the upper surface of a substrate and a pixel separator disposed to penetrate the substrate between the plurality of pixels, wherein each of the plurality of pixels comprises at least one photodiode and a pixel circuit below the at least one photodiode; and a logic circuit for acquiring a pixel signal from the plurality of pixels, wherein the pixel separator comprises a first pixel separator that extends along a first direction and a second direction that are parallel to the upper surface of the substrate and intersect each other and comprises polysilicon; and a second pixel separator that intersects the first direction and the second direction within the region formed by the first pixel separator and comprises an insulating material. Effects of the invention

[0012] According to an embodiment of the present invention, in an image sensor having a structure in which at least some of the pixels having color filters of the same color are adjacent to each other, the sensitivity of the image sensor can be improved by ensuring that the pixel separation film between the pixels having color filters of the same color does not include polysilicon.

[0013] According to an embodiment of the present invention, a pixel separation film between pixels having different color filters may include polysilicon, and since the pixel separation film is connected to a BCA (Backside Contact) to receive a negative bias voltage, it is possible to prevent degradation of the dark level characteristics of the image sensor.

[0014] 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

[0016] FIG. 1 is a simplified block diagram of an image sensor according to an embodiment of the present invention. FIGS. 2 and FIGS. 3 are drawings that simply illustrate a pixel circuit of an image sensor according to an embodiment of the present invention. FIG. 4 is a diagram simply showing a pixel array of an image sensor according to an embodiment of the present invention. FIGS. 5 and 6 are drawings for explaining a pixel array of an image sensor according to an embodiment of the present invention. FIGS. 7 to 17 are drawings for explaining a method for manufacturing an image sensor according to an embodiment of the present invention. FIGS. 18 to 23 are drawings for explaining a pixel array of an image sensor according to embodiments of the present invention. Specific details for implementing the invention

[0017] Hereinafter, preferred embodiments of the present invention are described as follows with reference to the attached drawings.

[0019] FIG. 1 is a simplified block diagram of an image sensor according to an embodiment of the present invention.

[0020] Referring to FIG. 1, the image sensor (1) may include a pixel array (10) and a logic circuit (20), etc.

[0021] A pixel array (10) may include a plurality of pixels (PX) arranged in an array form along a plurality of rows and a plurality of columns. Each of the plurality of pixels (PX) may include at least one photoelectric conversion element that generates a charge in response to light, and a pixel circuit that generates a pixel signal corresponding to the charge generated by the photoelectric conversion element. The photoelectric conversion element may include a photodiode formed of a semiconductor material, and / or an organic photodiode formed of an organic material.

[0022] 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 pixels (PX) may vary. For example, each of the pixels (PX) may include an organic photodiode containing an organic material, or may be implemented as a digital pixel. If the pixels (PX) are implemented as digital pixels, each of the pixels (PX) may include an analog-to-digital converter for outputting a digital pixel signal.

[0023] The logic circuit (20) may include circuits for controlling the pixel array (10). For example, the logic circuit (20) may include a row driver (21), a readout circuit (22), a column driver (23), control logic (24), etc. The row driver (21) can drive the pixel array (10) in units of row lines. For example, the row driver (21) 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) in units of row lines.

[0024] The readout circuit (22) may include a Correlated Double Sampler (CDS), an Analog-to-Digital Converter (ADC), etc. Correlated double samplers may be connected to pixels (PX) and column lines. Correlated double samplers may read pixel signals through column lines from pixels (PX) connected to a low line selected by a low line selection signal of the low driver (21). The analog-to-digital converter may convert the pixel signal detected by the correlated double sampler into a digital pixel signal and transmit it to the column driver (23).

[0025] The column driver (23) may include a latch or buffer circuit capable of temporarily storing a digital pixel signal and an amplification circuit, etc., and may process a digital pixel signal received from a readout circuit (22). The row driver (21), the readout circuit (22), and the column driver (23) may be controlled by control logic (24). The control logic (24) may include a timing controller, etc., for controlling the operation timing of the row driver (21), the readout circuit (22), and the column driver (23).

[0026] Among the pixels (PX), pixels (PX) that are positioned at the same location in the horizontal direction may share the same column line. For example, pixels (PX) that are positioned at the same location in the vertical direction may be simultaneously selected by the row driver (21) and may output pixel signals through the column lines. In one embodiment, the readout circuit (22) may simultaneously acquire pixel signals from the pixels (PX) selected by the row driver (21) through the column lines. The pixel signal may include a reset voltage and a pixel voltage, and the pixel voltage may be a voltage in which the charge generated in response to light at each of the pixels (PX) is reflected in the reset voltage.

[0027] Each of the pixels (PX) may include a color filter having a predetermined color, and depending on the color of the color filter, they may be classified into a red pixel configured to detect red light, a green pixel configured to detect green light, a blue pixel configured to detect blue light, etc. The color of the color filter is not necessarily limited to red, green, or blue, and depending on the embodiments, the color filter may have colors such as yellow or white.

[0028] At least some of the pixels configured to detect light of the same color in the pixel array (10) may be adjacent to each other. Pixels that are adjacent to each other and configured to detect light of the same color may share micro-lenses to provide an auto-focusing (AF) function for the image, or may include micro-lenses individually to provide an image with high sensitivity and a high signal-to-noise ratio (SNR).

[0029] External light can pass through a color filter and enter the photodiode of each pixel (PX). Depending on the direction of propagation of the light entering each pixel (PX), the light passing through the color filter may enter an adjacent pixel instead of the corresponding pixel. For example, light passing through the green color filter of a green pixel may enter the photodiode of an adjacent blue pixel or the photodiode of an adjacent red pixel. If such optical crosstalk occurs, image quality may be degraded.

[0030] To reduce the effect of optical crosstalk, a pixel isolation layer, such as Deep Trench Isolation (DTI), may be placed between pixels (PX) arranged in a pixel array of an image sensor (1). To form the pixel isolation layer, a first material with excellent light reflection properties may be deposited in a thin thickness on the side of a trench formed in a semiconductor substrate, and the space remaining after the first material is deposited may be filled with a second material. Silicon oxide may be used as the first material.

[0031] When polysilicon is used as the second material, the polysilicon can effectively prevent crosstalk between adjacent pixels and can accumulate holes around the pixel isolation film when connected to a negative bias voltage, thereby improving the dark level characteristics of the image sensor (1). However, due to the light-absorbing properties of polysilicon, the amount of light absorbed by the pixel isolation film may increase, and the sensitivity of the image sensor may decrease.

[0032] According to an embodiment of the present invention, a pixel separator may include a first pixel separator disposed between pixels (PX) that are adjacent to each other and configured to detect light of different colors, and a second pixel separator disposed between pixels that are adjacent to each other and configured to detect light of the same color, and the first pixel separator and the second pixel separator may be composed of different materials.

[0033] For example, the first pixel separator may include polysilicon to prevent crosstalk between pixels configured to detect different colors of light and minimize the degradation of the dark level characteristics of the image sensor (1). On the other hand, the second pixel separator may not include polysilicon and may include only silicon oxide. Since the second pixel separator does not include polysilicon, it may absorb less light compared to the first pixel separator, thus improving the sensitivity of the image sensor.

[0036] FIGS. 2 and FIGS. 3 are drawings that simply illustrate a pixel circuit of an image sensor according to an embodiment of the present invention.

[0037] First, referring to FIG. 2, 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.

[0038] 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).

[0039] 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).

[0040] 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).

[0041] In one embodiment illustrated in FIG. 2, 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. 4.

[0042] Referring to FIG. 3, two or more adjacent pixels may share at least some of the transistors included in the pixel circuit. In one embodiment illustrated in FIG. 4, four adjacent pixels may share a floating diffusion region (FD), a reset transistor (RX), driving transistors (DX1, DX2), and a select transistor (SX).

[0043] 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).

[0044] 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).

[0045] However, the pixel circuit described with reference to FIG. 3 is merely one example 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 a pixel can be implemented. Alternatively, the pixel circuit may vary depending on the number of transistors included in each pixel.

[0047] FIG. 4 is a diagram simply showing a pixel array of an image sensor according to an embodiment of the present invention.

[0048] Referring to FIG. 4, a pixel array (50) of an image sensor according to an embodiment of the present invention may include a plurality of pixels (51-53) arranged along a first direction (X) and a second direction (Y). For example, the pixel array (50) may include red pixels (51), green pixels (52), and blue pixels (53). Each of the red pixels (51) may include a red color filter, each of the green pixels (52) may include a green color filter, and each of the blue pixels (53) may include a blue color filter. However, depending on the embodiment, the pixel array (50) may further include at least one yellow pixel, at least one white pixel, etc.

[0049] In one embodiment illustrated in FIG. 4, pixels configured to detect light of the same color may form a pixel group. Microlenses may be shared among the pixels included in the pixel group. FIG. 4 illustrates, as an example, area A where a pixel group containing green pixels is located.

[0050] Groups of pixels configured to detect different colors may be adjacent to each other. For example, a group of green pixels may be adjacent to a group of blue pixels in a first direction (X) and to a group of red pixels in a second direction (Y).

[0051] For example, the pixel array (50) may include a photodiode array, a color filter array, and a microlens array. The photodiode array includes a plurality of photodiodes formed on a semiconductor substrate along a first direction and a second direction, and the plurality of photodiodes may be separated from each other in the first direction and the second direction by a pixel isolation film.

[0052] Meanwhile, the color filter array includes a plurality of color filters disposed on one surface of a semiconductor substrate along a first direction and a second direction, and the plurality of color filters can be separated from each other in the first direction and the second direction by a filter separator. A microlens array is disposed on the color filter array, and thus the color filter array can be disposed between the microlens array and the photodiode array in a third direction.

[0053] In one embodiment, a plurality of pixels (51-53) may each include photodiodes corresponding to one pixel, and may include color filters and microlenses shared by one or more pixels. In the example of FIG. 2, pixels arranged in a 2×2 matrix structure may share one color filter and one microlens. When multiple photodiodes process light from one microlens, an autofocus function (AF) can be implemented.

[0054] Meanwhile, if the direction of propagation of light incident on each of the multiple pixels (51-53) forms a predetermined angle with the third direction (Z), optical crosstalk may occur. For example, if the direction of propagation of light is not parallel to the third direction (Z) but is inclined toward the first direction (X), at least a portion of the light passing through the red color filter may flow into the green pixels (52) adjacent to the red pixels (51) in the first direction (X). Alternatively, at least a portion of the light passing through the green color filter may flow into the red pixels (51) adjacent to the green pixels (52) in the first direction (X). Optical crosstalk may also occur between the green pixels (52) and the blue pixels (53) according to a similar principle. Furthermore, optical crosstalk may also occur between adjacent red pixels (51), between green pixels (52), and between blue pixels (53).

[0055] According to an embodiment of the present invention, a first pixel separator disposed between pixels configured to detect light of different colors may include polysilicon. Due to the light-absorbing properties of polysilicon, optical crosstalk that may occur between pixels configured to detect light of different colors can be prevented.

[0056] On the other hand, a second pixel separator placed between pixels configured to detect light of the same color may include only silicon oxide. Since the second pixel separator, which does not include polysilicon, can absorb less light compared to the first pixel separator, the overall sensitivity of the image sensor may be improved.

[0057] Meanwhile, if the second pixel separator does not contain polysilicon, optical crosstalk may occur between pixels placed on both sides of the second pixel separator; however, since the pixels placed on both sides of the second pixel separator are configured to detect light of the same color, image quality degradation due to optical crosstalk can be minimized.

[0059] FIGS. 5 and 6 are drawings for explaining a pixel array of an image sensor according to an embodiment of the present invention.

[0060] For example, FIG. 5 may be an enlarged view of area A of the pixel array (50) described with reference to FIG. 2, and FIG. 6 may be a cross-sectional view showing the cross-section in the II' direction of FIG. 5.

[0061] Referring to FIGS. 5 and 6, a plurality of pixels (PX) may be arranged in a plurality of pixel regions arranged along a first direction (X) and a second direction (Y) parallel to the upper surface of the substrate (101). As described with reference to FIG. 2, pixels for detecting light of the same color that are adjacent to each other may form a pixel group. FIG. 5 illustrates a pixel group (PG) in which pixels (PX) for detecting light of the same color are arranged in a 2×2 matrix structure.

[0062] Multiple pixel groups may be defined by a first pixel separator (107). That is, a first pixel separator (107) may be placed between pixel groups. Adjacent pixel groups may include pixels for detecting different colors, and pixels for detecting different colors may be adjacent on both sides of the first pixel separator (107).

[0063] A plurality of pixels (PX) may be disposed on the inner side of the first pixel separator (107). The pixels (PX) included in the pixel group (PG) may be defined by the second pixel separator (108). The pixel group (PG) may include pixels for detecting light of the same color, and pixels for detecting light of the same color may be adjacent on both sides of the second pixel separator (108). The second pixel separator (108) may extend intersectingly in the first direction (X) and the second direction (Y) between the pixels within the area formed by the first pixel separator (107).

[0064] According to an embodiment of the present invention, the first and second pixel separators (107, 108) may be composed of different materials. For example, the first pixel separator (107) may include polysilicon, and the second pixel separator (108) may not include polysilicon and may be composed of silicon oxide.

[0065] Referring to FIG. 5, each of the plurality of pixels (PX) may include a pixel circuit region disposed inside the pixel isolation films (107, 108). For example, the pixel circuit region may include at least one transistor (110), a transmission gate structure (120), a floating diffusion region (130), and an impurity region (140), etc.

[0066] The floating diffusion region (130) is a region doped with a first conductivity type impurity and may be a region where charge generated in the photodiode accumulates. The floating diffusion region (130) may be adjacent to the transmission gate structure (120). The transmission gate structure (120) may be adjacent to the photodiode formed on the inner side of the pixel isolation film (105) in a third direction (Z-axis direction). For example, the first conductivity type impurity may be an N-type impurity. The shape of the floating diffusion region (110) is not limited as shown in FIG. 5 and may be varied in various ways according to embodiments.

[0067] When a first bias voltage is input to the transmission gate structure (120), the charge generated in the photodiode may not be able to move to the floating diffusion region (110). When the voltage of the transmission gate structure (120) is increased to a second bias voltage higher than the first bias voltage, the charge generated in the photodiode may move to the floating diffusion region (110). For example, the first bias voltage may be a negative 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.

[0068] The transistor (110) may provide at least one of a reset transistor, a select transistor, and a driving transistor included in the pixel circuit. As previously described with reference to FIG. 3, the pixel circuit may be implemented by two or more adjacent pixels (PX) sharing the transistor (110). Referring to FIG. 5, the transistor (110) may include a gate structure (112) and source / drain regions (111) on both sides of the gate structure (112). In one embodiment, the area of ​​each source / drain region (111) may be smaller than the area of ​​the floating diffusion region (130). This may be because the area of ​​the floating diffusion region (130), where the charge generated in the photodiode accumulates, must be relatively larger.

[0069] Each of the plurality of pixels (PX) may include at least one impurity region (140) separated from the floating diffusion region (130) and the transistor (110). For example, as shown in FIG. 5, the floating diffusion region (110) may be disposed on one side of the transmission gate structure (120), and the impurity region (140) may be disposed on the other side of the transmission gate structure (120). However, the impurity region (140) may not be in direct contact with the transmission gate structure (120) and may be separated from the transmission gate structure (120) by a device isolation film. In one embodiment, the impurity region (140) may be doped with an impurity of a second conductivity type different from the source / drain region (111) of the floating diffusion region (130) and the transistor (110). A ground voltage may be input to the impurity region (140).

[0070] Referring together with FIG. 6, the substrate (101) of the image sensor (100) may include a first surface and a second surface facing each other in a third direction (Z). For example, an optical unit may be disposed on the first surface, and wiring patterns (150) and an interlayer insulating layer (160) may be disposed on the second surface. The wiring patterns (150) may provide a pixel circuit by connecting a transistor (110), a transmission gate structure (120), a floating diffusion region (130), and an impurity region (140) to each other. The interlayer insulating layer (160) may include a plurality of interlayer insulating layers (161-163) and may cover the transistor (110), the transmission gate structure (120), the floating diffusion region (130), the impurity region (140), and the wiring patterns (150). For example, the interlayer insulating layer (160) can be formed of silicon oxide, silicon nitride, etc.

[0071] An optical portion disposed on a first surface of a substrate (101) may include a horizontal insulating layer (170), a filter separator (180), color filters (181), a flattening layer (183), and micro lenses (184).

[0072] According to an embodiment, a single microlens (184) and a single color filter (182) may be shared among pixels (PX) included in a single pixel group (PG). The filter separator (180) may have a checkerboard shape extending in a first direction (X) and a second direction (Y), similar to the pixel separator (107), and adjacent color filters (182) in the first direction (X) and the second direction (Y) may be separated from each other by the filter separator. The filter separator (180) and the color filters (182) provide a color filter array, and the microlenses (184) may provide a microlens array. Meanwhile, a second pixel separator (108) extending in the first direction (X) and the second direction (Y) may intersect at the center of the microlens (184).

[0073] Light passing through the optical section can be incident on a photodiode (PD) included in each of the plurality of pixels (PX). In the embodiment illustrated in FIGS. 5 and 6, each of the plurality of pixels (PX) is shown as including one photodiode (PD), but according to the embodiments, at least one of the plurality of pixels (PX) may include two or more photodiodes (PD).

[0074] Light entering the image sensor (100) can first be refracted by micro-lenses (184), pass through a flattening layer (183), and enter color filters (181). Light of a predetermined wavelength band is filtered by the color filters (181), and filtered light can pass through a horizontal insulating layer (170) and enter the photodiode (PD) of each of the plurality of pixels (PX).

[0075] According to an embodiment of the present invention, the first pixel separator (107) and the second pixel separator (108) may be implemented with different materials. Specifically, silicon oxide with excellent light reflection properties may be deposited on the surface of the first pixel separator (107), and polysilicon may be filled in the space remaining after the silicon oxide is deposited. That is, in the first pixel separator (107), the silicon oxide may come into contact with the substrate (101), and polysilicon may be placed inside the silicon oxide. Accordingly, as shown in FIG. 6, the problem of light passing through a color filter entering into a pixel configured to detect light of a different color can be prevented.

[0076] The second pixel separator (108) may be formed solely of silicon oxide. As illustrated in FIG. 6, some of the light that passes through a color filter and reaches the second pixel separator (108) may be reflected from the second pixel separator (108), while other parts may pass through the second pixel separator (108) and flow into adjacent pixels. That is, crosstalk may occur between pixels configured to detect light of the same color. However, crosstalk between pixels configured to detect light of the same color may not have a significant adverse effect on the quality of the image, and rather, the sensitivity of the image sensor may be improved because the amount of light absorbed by the pixel separator is reduced.

[0078] FIGS. 7 to 17 are drawings for explaining a method for manufacturing an image sensor according to an embodiment of the present invention.

[0079] First, referring to FIGS. 7 to 9, a method for manufacturing an image sensor according to an embodiment of the present invention may begin by forming pixel separation films (107, 108) on a substrate (101) comprising a semiconductor material to define a plurality of pixel regions (PA) in which a plurality of pixels are to be formed. As previously described, the pixel separation films (107, 108) may extend in a first direction (X) and a second direction (Y). A plurality of pixel regions (PA) arranged along the first direction (X) and the second direction (Y) may be defined by the pixel separation films (107, 108).

[0080] Specifically, referring to FIG. 7, trenches extending in a third direction (Z) perpendicular to one surface of the substrate (101) may be formed, and on the sides of the trenches, a thin thickness, for example, 200 Silicon oxide (105) can be deposited with a thickness of less than or equal to the following. There may be gaps remaining in the trenches where the silicon oxide (105) is deposited.

[0081] Referring to FIG. 8, a first pixel separator (107) can be formed by filling a portion of the trenches where silicon oxide (105) is deposited with polysilicon (106). A pixel group can be defined by the first pixel separator (107).

[0082] Referring to FIG. 9, a second pixel separation film (108) can be formed by filling the remaining trenches where polysilicon (106) is not filled among the trenches where silicon oxide (105) is deposited with silicon oxide. Pixel regions (PA) can be defined by the pixel separation films (107, 108).

[0083] Meanwhile, in the example of FIG. 9, the thickness (W1) of the first pixel separator (107) and the thickness (W2) of the second pixel separator (108) may be formed to be the same. In order to form the pixel separators (107, 108) to have the same thickness, silicon oxide may be formed twice as described in FIG. 7 and FIG. 9 when forming the second pixel separator (108). However, the process of forming the pixel separators (107, 108) or the thickness of the pixel separators (107, 108) in the present invention is not limited to those described with reference to FIG. 7 to FIG. 9.

[0084] In each of the plurality of pixel regions (PA), a photodiode (PD) may be formed as shown in FIG. 10. However, depending on the embodiments, the photodiode (PD) may be replaced with another photoelectric conversion element. The photodiode (PD) may be formed by a process of doping a substrate (101) with a predetermined impurity. For example, the photodiode (PD) may be formed at a predetermined depth from the upper surface of the substrate (301).

[0085] Next, referring to FIG. 11, a pixel circuit region may be formed. The pixel circuit region may include a transmission gate structure (120), a floating diffusion region (130), and an impurity region (140) formed on a substrate (101), wiring patterns (150) and an interlayer insulating layer (160) formed on the substrate (101), etc. According to an embodiment, the pixel circuit region may further include at least one transistor in addition to the transmission gate structure (120), the floating diffusion region (130), and the impurity region (140). The interlayer insulating layer (160) may include a plurality of interlayer insulating layers (161-163). The elements included in the pixel circuit region may be connected to each other by the wiring patterns (150) to provide a pixel circuit.

[0086] Next, referring to FIGS. 11 to 13, a substrate (101) formed up to the pixel circuit area may be flipped over, and a Chemical-Mechanical Polishing (CMP) process may be performed to remove a portion of the substrate (101). As shown in FIGS. 11 to 13, the thickness of the substrate (101) may be reduced by the CMP process, and the distance between the photodiode (PD) and one side of the substrate (101) may be reduced. According to an embodiment, the pixel isolation films (107, 108) may be formed as Front Deep Trench Isolation (FDTI) and completely penetrate the substrate (101). In other words, in an embodiment shown in FIG. 13, a portion of the substrate (101) is removed by the CMP process, so that the first side of the substrate (101) can form a co-surface with one side of the pixel isolation films (107, 108). Therefore, in the third direction (Z), the thickness of the substrate (101) and the thickness of the pixel separation films (107, 108) may be the same.

[0087] Referring to FIG. 14, a horizontal insulating layer (170) may be formed on a first surface of a substrate (101). The horizontal insulating layer (170) may be formed from a high dielectric constant material having a dielectric constant higher than that of silicon oxide, for example, aluminum oxide. The horizontal insulating layer (170) may include a plurality of layers, and if the horizontal insulating layer (170) includes a plurality of layers, at least some of them may be formed from different materials. For example, among the plurality of layers, the layer in direct contact with the substrate (101) may be formed from a high dielectric constant material. By forming such a horizontal insulating layer (170), defects occurring on the substrate (101) by a CMP process, etc., can be cured.

[0088] For example, dangling bonds may occur on the substrate (101) due to a CMP process, and excess charge may be generated as a result. The excess charge generated by dangling bonds, etc. is indistinguishable from the photocharge generated by the photodiode (PD) in response to light, and thus degrades the dark level characteristics of the image sensor and may cause white spots to appear in the image. The horizontal insulating layer (170) can improve the dark level characteristics of the image sensor and minimize the occurrence of white spots by curing such defects and removing excess charge.

[0089] Referring to FIG. 15, a sacrificial layer (115) may be formed on a horizontal insulating layer (170), and a mask layer (116) may be formed on the sacrificial layer (115). For example, the mask layer (116) may be formed at a position corresponding to the first pixel separator (107) in the first direction (X) and the second direction (Y), and the sacrificial layer (115) may be exposed in each of the plurality of pixel regions (PA) by the mask layer (116).

[0090] When the mask layer (116) is formed, a filter separator (180) can be formed by performing an etching process to remove the sacrificial layer (115) in the area exposed by the mask layer (116) as shown in FIG. 16. The filter separator (180) can be formed in a position corresponding to the first pixel separator (107) and extends in the first direction (X) and the second direction (Y). In the example of FIG. 16, the filter separator (180) is shown to have a width smaller than that of the first pixel separator (107), but it is not necessarily limited to this shape.

[0091] Next, referring to FIG. 17, color filters (181) may be formed between filter separators (180), and a flattening layer (183) and micro lenses (184) may be formed on the color filters (181). Referring to FIG. 17, one color filter (181) and one micro lens (184) may be shared among pixels included in a pixel group.

[0092] As previously described, in the operation of the image sensor (100), light passing through one of the color filters (381) can be incident on a photodiode (PD) placed in each of the plurality of pixel regions (PA). In order to improve the sensitivity of the image generated by the image sensor (100), it is desirable that as much light as possible passing through the color filter (381) is introduced into the photodiode (PD). That is, the absorption of light passing through the color filter (181) by the pixel separator (107, 108) must be minimized. According to an embodiment of the present invention, the second pixel separator (108) between pixels included in a single pixel group may not contain polysilicon and may be composed only of silicon oxide. Since the pixel separator (108) can absorb less light than the pixel separator (107) containing polysilicon, the sensitivity of the image can be improved.

[0093] In particular, as illustrated in FIG. 17, when pixels included in a single pixel group have a 2×2 matrix structure and share a single microlens, light from the microlens can be most concentrated at the point where the second pixel separator (108) intersects in the first direction (X) and the second direction (Y). According to an embodiment of the present invention, since the pixel separator (108) can absorb less light than the pixel separator (107), the photodiode (PD) can effectively receive light reflected from the point where the light is most concentrated. Therefore, the sensitivity of the image can be more effectively improved.

[0095] Meanwhile, according to an embodiment of the present invention, the first pixel separator (107) may still include polysilicon. According to an embodiment, by applying a negative bias voltage to the first pixel separator (107), the occurrence of dark current in the image sensor can be mitigated and the dark characteristics of the image sensor can be improved. An example of an image sensor in which dark characteristics can be improved is described with reference to FIGS. 18 and 19.

[0096] FIGS. 18 and FIGS. 19 are drawings for explaining a pixel array of an image sensor according to an embodiment of the present invention.

[0097] FIG. 18 is a simplified diagram illustrating a pixel array of an image sensor according to an embodiment of the present invention. Referring to FIG. 18, the pixel array (60) of the image sensor according to an embodiment of the present invention may include a plurality of pixels (61-64) arranged along a first direction (X) and a second direction (Y). For example, the pixel array (60) may include red pixels (61), green pixels (62), and blue pixels (63) in the center. The red pixels (61), green pixels (62), and blue pixels (63) may be referred to as color pixels (61-63). The pixel array (60) may further include dummy pixels (64) in the periphery of the color pixels (61-63).

[0098] Color pixels (61-63) may correspond to the pixels (51-53) described with reference to FIG. 2. Dummy pixels (64) may be defined by a pixel separator similar to the color pixels (61-63). However, dummy pixels (64) may not include a microlens and a color filter.

[0099] According to an embodiment of the present invention, a third pixel separator disposed between dummy pixels may comprise polysilicon, similar to the first pixel separator. The third pixel separator may be electrically connected to the first pixel separator and may receive a negative bias voltage from the outside through a conductive contact.

[0100] FIG. 19 is a cross-sectional view showing the II-II' direction and III-III' direction cross-section of FIG. 18.

[0101] The II-II' direction cross-section represents a cross-section of pixels included in a pixel group, and the III-III' direction cross-section represents a cross-section of a dummy pixel. The II-II' direction cross-section may be similar to that shown in FIG. 17.

[0102] Referring to FIG. 19, the substrate (201), the interlayer insulating layer (260), and the horizontal insulating layer (270) may extend into the dummy pixel area. A third pixel separator (217) may be formed in the substrate (201) of the dummy pixel area in the same way as the first pixel separator (207) is formed. That is, the third pixel separator (217) may be formed by depositing silicon oxide (216) in the trench of the substrate (201) and filling the remaining space with polysilicon (216).

[0103] The dummy pixel area may further include a conductive contact (290). The conductive contact (290) is electrically connected to an external wiring layer (not shown) to apply a negative bias voltage to the third pixel separator. As shown in FIG. 18, the pixel separators may be formed in a first direction (X) and a second direction (Y) to form a grid pattern. Thus, the first pixel separator (207) and the third pixel separator (217) may be electrically connected. Meanwhile, the second pixel separator (208) may only include an insulating material having a resistivity lower than that of polysilicon, and a negative bias voltage may not be applied to the second pixel separator (208).

[0104] When a negative bias voltage is applied through the conductive contact (290), holes within the substrate (101) can move toward and accumulate on the interface of the first pixel separator (107). Accordingly, the dark current generation of the image sensor can be reduced, and the dark characteristics of the image generated by the image sensor can be improved.

[0105] Meanwhile, in the example of FIG. 19, the conductive contact (290) is provided on the horizontal insulating layer (270) of the substrate, but alternatively, the conductive contact may be provided on the interlayer insulating layer (260).

[0107] As described with reference to FIGS. 2 through 19, the present invention may be applied in cases where pixels included in a pixel group have a matrix structure and share a single microlens. However, the present invention is not limited thereto. Specifically, the present invention may also be applied in a structure in which adjacent pixels for detecting light of the same color form a pixel group, where each pixel included in the pixel group includes a microlens. Hereinafter, embodiments of the present invention are described in detail with reference to FIGS. 20 through 23.

[0108] FIG. 20 is a diagram simply showing a pixel array of an image sensor according to an embodiment of the present invention.

[0109] Referring to FIG. 20, the pixel array (70) of an image sensor according to an embodiment of the present invention may include a plurality of pixels (71-73) arranged along a first direction (X) and a second direction (Y). The pixels (71-73) arranged in the pixel array (70) may be arranged similarly to the pixels (51-53) described with reference to FIG. 2. That is, pixels configured to detect light of the same color may be arranged in a 2×2 matrix structure to form a pixel group.

[0110] However, referring to FIG. 20, the pixels included in a pixel group may each include a microlens. An image obtained from an image sensor in which each pixel has a microlens may have excellent signal-to-noise ratio (SNR) and sensitivity. Meanwhile, some of the adjacent pixels included in different pixel groups may share a microlens (75) with each other, and these pixels may provide an autofocus function (AF).

[0111] According to an embodiment of the present invention, even when pixels included in a pixel group each include a microlens, a first pixel separator disposed between pixel groups may include polysilicon, and a second pixel separator between adjacent pixels within a pixel group may be composed solely of silicon oxide without including polysilicon. Since the second pixel separator can absorb less light than the first pixel separator, the sensitivity of the image sensor may be improved.

[0112] FIG. 21 is a drawing for explaining a pixel array of an image sensor according to an embodiment of the present invention. Specifically, FIG. 21 may be a cross-sectional view showing a cross-section in the direction of IV-IV' of FIG. 20.

[0113] The image sensor (300) illustrated in FIG. 21 may have a structure similar to the image sensor (100) described with reference to FIG. 6. However, the pixels included in the image sensor (300) may each have a micro lens (384) and a color filter (382).

[0114] According to an embodiment of the present invention, silicon oxide (305) may be deposited on the surface of a first pixel separator (307) disposed between pixels having different color filters, and polysilicon (306) may be filled in the space remaining after the silicon oxide is deposited. Accordingly, the occurrence of crosstalk between pixels for detecting different colors of light may be prevented.

[0115] According to an embodiment, the image sensor (300) may further include dummy pixels and a third pixel separator disposed between the dummy pixels, and the first pixel separator (307) may be connected to the third pixel separator in a manner similar to that described with reference to FIG. 19 and receive a negative bias voltage. Thus, the dark characteristics of the image obtained through the image sensor (300) may be improved.

[0116] And, the second pixel separator (308) placed between pixels having the same color filter may not contain polysilicon and may be filled with silicon oxide. Since the second pixel separator (308) can absorb a smaller amount of light compared to the first pixel separator (307), the sensitivity of the image sensor may be improved.

[0117] FIG. 22 is a diagram simply showing a pixel array of an image sensor according to an embodiment of the present invention.

[0118] Referring to FIG. 22, a pixel array (80) according to an embodiment of the present invention may include a plurality of pixels (81-83) arranged along a first direction (X) and a second direction (Y). Among the pixels arranged in the pixel array (80), pixels configured to detect light of the same color may be arranged in a 3×3 matrix structure to form a pixel group.

[0119] Referring to FIG. 22, pixels included in a pixel group may each include a microlens. Meanwhile, some adjacent pixels included in different pixel groups may share a microlens with each other, and these pixels may provide an autofocus (AF) function.

[0120] FIG. 23 is a drawing for explaining a pixel array of an image sensor according to an embodiment of the present invention. Specifically, FIG. 23 is a cross-sectional view showing a cross-section in the V-V' direction of FIG. 22.

[0121] The image sensor (400) illustrated in FIG. 23 shows a form in which three pixels for detecting light of the same color are adjacent in a first direction (X). Referring to FIG. 22 and FIG. 23, nine pixels for detecting light of the same color form a pixel group and may be adjacent in a first direction (X) and a second direction (Y). Each pixel included in the pixel group may have a micro lens (484) and a color filter (482).

[0122] According to an embodiment of the present invention, silicon oxide (405) may be deposited on the surface of a first pixel separator (407) disposed between pixels having different color filters, and polysilicon (406) may be filled in the space remaining after the silicon oxide is deposited. Additionally, a second pixel separator (408) disposed between pixels having the same color filters may be filled with silicon oxide without containing polysilicon. Thus, image sensitivity can be improved while minimizing image quality degradation caused by crosstalk between adjacent pixels.

[0124] According to an embodiment of the present invention described with reference to FIGS. 1 to 23, a first pixel separator disposed between pixels configured to detect different colors and a second pixel separator disposed between pixels configured to detect the same color may be composed of different materials. Specifically, the first pixel separator may include polysilicon, and the second pixel separator may not include polysilicon and may be composed of silicon oxide.

[0125] The first pixel isolation layer can have a lower transmittance than the second pixel isolation layer, so it can prevent optical crosstalk between adjacent pixels. Also, since the first pixel isolation layer is conductive, when an external negative bias voltage is applied, holes accumulate around it, and dark characteristics can be improved.

[0126] Since the second pixel isolation layer can have a higher transmittance compared to the first pixel isolation layer, light passing through the microlens can effectively be incident on the photodiode without being absorbed by the second pixel isolation layer. Although optical crosstalk may occur between adjacent pixels on both sides of the second pixel isolation layer, crosstalk between pixels detecting light of the same color may not significantly adversely affect image quality. Therefore, image sensitivity can be effectively improved while minimizing image quality degradation.

[0128] 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

[0130] 100, 200, 300, 400: Image sensor PX: Pixel PD: Photodiode 101, 201, 301, 401: Board 107, 207, 307, 407: 1st pixel separator 108, 208, 308, 408: 2nd pixel separator 120, 220, 320, 420: Transmission gate structure 130, 230, 330, 430: Floating diffusion area 140, 240, 340, 440: Impurity region 170, 270, 370, 470: Horizontal insulation layer 180, 280, 380, 480: Filter separator 182, 282, 382, ​​482: Color filters 183, 283, 383, 483: Leveling layer 184, 284, 384, 484: Microlenses

Claims

Claim 1 An image sensor comprises: a substrate including a first surface and a second surface opposite thereto; a first pixel group including a plurality of first photodiodes arranged in an L / L matrix structure in a plane and a first single color filter formed on the plurality of first photodiodes; a second pixel group including a plurality of second photodiodes arranged in an L / L matrix structure in the plane and a second single color filter formed on the plurality of second photodiodes; and a first insulating trench penetrating at least a portion of the substrate from the second surface between the first pixel group and the second pixel group. The image sensor comprises a second insulating trench penetrating at least a portion of the substrate from the second surface between the plurality of second photodiodes, wherein the first insulating trench is filled with N layers, each layer extending from the second surface toward the first surface, and the second insulating trench is filled with M layers, each layer extending from the second surface toward the first surface, N and M are each integers greater than or equal to 1, L is an integer greater than or equal to 2, N is different from M, the first pixel group is adjacent to the second pixel group, and the image sensor is configured to receive light incident through the second surface, and the first single color filter and the second single color filter transmit light of different colors. Claim 2 In paragraph 1, the above N is an image sensor larger than M. Claim 3 An image sensor according to claim 1, wherein the N layers comprise a first material and the M layers comprise a second material different from the first material. Claim 4 In paragraph 3, the second material is an image sensor that is an insulating material. Claim 5 In paragraph 4, the image sensor is the second material being silicon oxide. Claim 6 In paragraph 4, the N layers are an image sensor comprising silicon oxide. Claim 7 In paragraph 4, the first pixel group further comprises a transmission gate structure, and at least a portion of the transmission gate structure extends from the first surface into the substrate of the image sensor. Claim 8 In paragraph 4, the image sensor comprises a horizontal insulating layer formed on the second surface, and the horizontal insulating layer comprises aluminum. Claim 9 In claim 8, the substrate further comprises a dummy pixel region and a third insulating trench formed within the dummy pixel region, wherein the third insulating trench is filled with N layers, and each layer extends from a second surface toward a first surface. Claim 10 In claim 9, the image sensor further comprises a plurality of micro-lenses arranged in an LХL matrix structure in a plane, wherein the first pixel group is a first pixel group.

Images