Image sensor, manufacturing method and electronic device

Abstract

The application provides an image sensor, a preparation method and an electronic device. The image sensor comprises a pixel array layer, a color film layer and a lens array layer which are stacked in sequence along a stacking direction; the pixel array layer comprises at least one target focusing pixel group; the lens array layer comprises at least one target lens; the color film layer comprises at least one target color film structure, the target color film structure corresponds to the target lens one by one, and in the stacking direction, a first projection area of the target color film structure is smaller than a second projection area of the target focusing pixel group. When the image is out of focus, the formed light spot deviates from the position of the light spot in the in-focus state, part of the light spot enters the area where the target color film structure is not arranged, the light entering the area is not filtered, the light signal of the area is significantly enhanced, a larger signal response difference appears in the target focusing pixel group, the separation ratio becomes larger, the sensitivity of the automatic focusing is improved, and the image quality is not affected.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to an image sensor, a fabrication method, and an electronic device. Background Technology

[0002] In image sensors, the basic principle of Phase Detection Auto Focus (PDAF) is that when an image is out of focus, the amount of light received by the two focusing pixels (also called PDAF pixels) differs. By adjusting to reduce this difference, focusing is achieved. Specifically, the two focusing pixels share a lens, located on opposite sides below the lens. When the image is out of focus, the incident light shifts, causing a difference in the response of the two focusing pixels. The angle of change of the incident light changes in opposite directions when the image is in focus or out of focus, causing the responses of the two focusing pixels to change in opposite directions as well. By sensing this change, the direction and magnitude of the change in the lens focal length in the camera module can be determined, thus achieving fast autofocus. The Segregation Ratio (SR) is the difference in response between the two focusing pixels when out of focus, reflecting the focusing sensitivity. A larger SR indicates a greater response difference, resulting in more accurate focusing and higher autofocus sensitivity.

[0003] However, the core requirement of an image sensor is to ensure that the image and color are not distorted, which means that the signal distribution of each pixel must be uniform after focusing is completed. Therefore, it is necessary to carefully measure the uniformity of pixel signals and the sensitivity of autofocus.

[0004] Typically, priority is given to ensuring pixel signal uniformity and chromatic aberration, which directly affect image quality, while the separation ratio, which characterizes autofocus sensitivity, is sacrificed to some extent. Therefore, how to improve the separation ratio and enhance autofocus sensitivity without compromising image quality has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide an image sensor, a manufacturing method, and an electronic device that can improve the sensitivity of autofocus while ensuring image quality. The specific solution is as follows:

[0006] This application provides an image sensor, characterized in that it comprises:

[0007] The pixel array layer, color filter layer, and lens array layer are stacked sequentially along the stacking direction;

[0008] The pixel array layer includes at least one target focusing pixel group; the lens array layer includes at least one target lens;

[0009] The color filter layer includes at least one target color filter structure, which corresponds one-to-one with the target lens. In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group.

[0010] In one possible implementation, when light is obliquely incident on the target lens, the light has a stacking component in the stacking direction and a target component in the target direction; the target direction is a first direction or a second direction, and the first direction and the second direction are perpendicular to each other with respect to the stacking direction.

[0011] In the target direction, the first length of the target color filter structure is less than the second length of the target focusing pixel group.

[0012] In one possible implementation, the target direction is the first direction and the second direction;

[0013] In the target direction, the first length of the target color filter structure is less than or equal to the second length of the target focusing pixel group.

[0014] In one possible implementation, the first projected area of ​​the target color filter structure is greater than or equal to the spot area generated by the focused light from the target lens;

[0015] In the stacking direction, the projection of the target color filter structure completely covers the target projection of the light spot, which is the projection of the light spot when in focus.

[0016] In one possible implementation, the center of the target focusing pixel group may or may not coincide with the center of the target sub-color filter structure.

[0017] In one possible implementation, the target focusing pixel group includes a 2*2 pixel structure, a 2*1 pixel structure, a dual-pixel structure, or a semi-masked pixel structure; the target focusing pixel group includes a first focusing pixel and a second focusing pixel, and focusing is achieved by the difference in the response of the first focusing pixel and the second focusing pixel to the light signal.

[0018] In one possible implementation, the projected shape of the target color filter structure in the stacking direction includes a rectangle, a circle, or a cross.

[0019] This application also provides a method for fabricating an image sensor, comprising:

[0020] A pixel array layer is formed, the pixel array layer including at least one target focusing pixel group;

[0021] A color filter layer is formed on one side of the pixel array layer, the color filter layer including at least one target color filter structure;

[0022] A lens array layer is formed on the side of the color filter layer away from the pixel array layer, and the lens array layer includes at least one target lens;

[0023] The target lens corresponds one-to-one with the target color filter structure;

[0024] In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group.

[0025] In one possible implementation, a color filter layer is formed on one side of the pixel array layer, including:

[0026] A color filter material layer is formed on one side of the pixel array layer;

[0027] The color filter material layer is photolithographically processed by a preset mask pattern to obtain the color filter layer; the preset mask pattern includes at least one target mask area, the target mask area includes a light-shielding area and a light-transmitting area, and the target color filter structure is formed by the light-shielding area during the photolithography process.

[0028] This application also provides an electronic device including the aforementioned image sensor.

[0029] This application provides an image sensor, a fabrication method, and an electronic device. The image sensor includes a pixel array layer, a color filter layer, and a lens array layer stacked sequentially along a stacking direction. The pixel array layer includes at least one target focusing pixel group; the lens array layer includes at least one target lens; and the color filter layer includes at least one target color filter structure, with each target color filter structure corresponding to a target lens. In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group. Thus, during focusing, since the target color filter structure does not completely cover the area where the target focusing pixel group is located, when the image is out of focus, light will obliquely enter the target lens, and the resulting light spot will deviate from its position when in focus. Some light spots will enter areas where the target color filter structure is not present. Light entering these areas will not be filtered, resulting in a significant increase in the light signal in these areas. Consequently, a large difference in signal response will appear in the target focusing pixel group, increasing the separation ratio and thus improving the sensitivity of autofocus. Furthermore, since the target color filter structure is still present in some areas, pixel uniformity is ensured, and image quality is not affected. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A cross-sectional schematic diagram of an image sensor provided in an embodiment of this application is shown;

[0032] Figure 2 A top view of an image sensor provided in an embodiment of this application is shown;

[0033] Figure 3 A top view of yet another image sensor provided in an embodiment of this application is shown;

[0034] Figure 4 This illustration shows a structural schematic diagram of an image sensor provided in an embodiment of this application;

[0035] Figure 5 This paper shows a schematic diagram of the structure of another image sensor provided in an embodiment of this application;

[0036] Figure 6 A top view of yet another image sensor provided in an embodiment of this application is shown;

[0037] Figure 7 A top view of yet another image sensor provided in an embodiment of this application is shown;

[0038] Figure 8 A top view of yet another image sensor provided in an embodiment of this application is shown;

[0039] Figure 9 A top view of yet another image sensor provided in an embodiment of this application is shown;

[0040] Figure 10 A schematic flowchart of a method for fabricating an image sensor according to an embodiment of this application is shown. Detailed Implementation

[0041] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0042] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0043] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0044] For ease of understanding, the following detailed description, in conjunction with the accompanying drawings, provides an image sensor, a fabrication method, and an electronic device according to embodiments of this application.

[0045] refer to Figure 1 The image shown is a cross-sectional schematic diagram of an image sensor provided in an embodiment of this application, including a pixel array layer 11, a color filter layer 12, and a lens array layer 13 stacked sequentially along the stacking direction.

[0046] Image sensors are used to convert light signals into electrical signals, thereby generating images. Image sensors can be, for example, charge-coupled device (CCD) image sensors, complementary metal-oxide-semiconductor (CMOS) image sensors, or other types of image sensors.

[0047] The pixel array layer 11 may include at least one target focusing pixel group 14. Specifically, the pixel array layer 11 may include at least one pixel 111, which is used to convert light signals into electrical signals to achieve photoelectric conversion. The pixel 111 may be, for example, a photodiode (PD). At least one pixel 111 can form a focusing pixel group, which can be used to achieve focusing. Any focusing pixel group can be referred to as the target focusing pixel group 14.

[0048] The lens array layer 13 may include at least one target lens. Specifically, the lens array layer 13 may include at least one lens 131, which may be, for example, a microlens 131. Multiple lenses 131 may be arranged in an array, and each lens 131 corresponds to a pixel 111. One pixel 111 may be disposed below each lens 131, or multiple pixels 111 may be disposed below each lens 131. Light passes through the lens 131 and is incident on the pixel 111. The pixel 111 can convert the received light signal into an electrical signal to generate an image.

[0049] The lens 131 located directly above the target focusing pixel group 14 can be used as the target lens 1311. In the stacking direction, the projection of the target lens 1311 can at least partially cover the projection of the target focusing pixel group 14. The stacking direction can be vertical, such as vertically upward or vertically downward. As an example, if the projection of the target lens 1311 is, for example, a circle, and the projection of the target focusing pixel group 14 is, for example, a rectangle, then the circle can be located inside the rectangle.

[0050] The target focusing pixel group 14 includes a first focusing pixel 141 and a second focusing pixel 142. That is, the lens array layer 13 has a target lens 1311, and the pixels 111 located directly below the target lens 1311 can form the target focusing pixel group 14, which includes two focusing pixels: the first focusing pixel 141 and the second focusing pixel 142. The focusing pixels are used to achieve focusing; the specific relationship between the focusing pixels and the pixels 111 in the pixel array layer 11 will be explained later.

[0051] The target focusing pixel group 14 is used to achieve focusing when light is incident on the target lens 1311 by adjusting the difference in the response of the first focusing pixel 141 and the second focusing pixel 142 to the light signal. In short, when the image is out of focus, light will obliquely enter the target lens 1311, and the amount of light will not be evenly distributed between the two focusing pixels. One focusing pixel will receive more light than the other, resulting in a difference in the amount of light between the two focusing pixels. Consequently, the electrical signals converted from the light signals also differ, meaning their responses to the light signals are different. By adjusting this difference to zero, the amount of light entering the two focusing pixels is equal, thus achieving focusing and resulting in the highest image sharpness.

[0052] The color filter layer 12 is used to filter light. The color filter layer 12 may include at least one color filter structure 121, with one color filter structure 121 corresponding to one lens 131. That is, the portion of the color filter layer 12 located below the lens 131 can be referred to as color filter structure 121, and each lens 131 has a color filter structure 121 directly below it. The color filter structure 121 can be used to allow light of a specific color to pass through, such as allowing red light to pass through, so that the pixel 111 located below the color filter structure 121 will only convert the red light signal into an electrical signal. The color filter structure 121 can also allow blue or green light to pass through.

[0053] The color filter layer 12 includes at least one target color filter structure 1211, which corresponds one-to-one with the target lens 1311. That is, the color filter structure 121 located directly below the target lens 1311 can be referred to as the target color filter structure 1211 corresponding to the target lens 1311.

[0054] refer to Figure 1As shown, the stacking direction is vertically upward, and light is incident from top to bottom. The image sensor includes a lens array layer 13, a color film layer 12, and a pixel array layer 11 stacked in sequence from top to bottom. There are 3 lenses 131 in the lens array layer 13. The middle lens 131 is taken as the target lens 1311, and the color film structure 121 directly below the target lens 1311 is taken as the target color film structure 1211. There are 6 pixels 111 in the pixel array layer 11. The two pixels 111 directly below the target color film structure 1211 form the target focus pixel group 14, and the two pixels 111 are respectively used as the first focus pixel 141 and the second focus pixel 142.

[0055] In the stacking direction, the first projected area of the target color film structure 1211 can be smaller than the second projected area of the target focus pixel group 14. Refer to Figure 2 As shown, it is a top view of an image sensor provided by an embodiment of the present application. Figure 2 The adjacent first focus pixel 141 and second focus pixel 142 are shown. The larger ellipse is the target lens 1311, the smaller ellipse is the area where the light spot 15 is located, and the square area is the target color film structure 1211. The light spot 15 is formed after the target lens focuses light.

[0056] The area of the projection of the target color film structure 1211 in the stacking direction is denoted as the first projected area S 1, and the area of the projection of the target focus pixel group 14 in the stacking direction is denoted as the second projected area S 2, and S 1 < S 2. In other words, the projection boundary of the target color film structure 1211 is located within the projection boundary of the target focus pixel group 14, or there is partial overlap.

[0057] In other words, compared with the related art in which the color film layer 12 completely covers the pixel array layer 11, in the present application, the color film layer 12 partially covers the pixel array layer 11, that is, the first projected area of the target color film structure 1211 is smaller than the second projected area of the target focus pixel group 14. A part of the area of the target focus pixel group 14 (such as the edge area) is a completely transparent area, that is, light can directly enter the underlying focus pixels without passing through the filtering process.

[0058] Furthermore, during the focusing process, since the target color film structure 1211 does not completely cover the area where the target focus pixel group 14 is located, when the image is out of focus and light is obliquely incident on the target lens 1311, the formed light spot 15 will deviate from the position where the light spot is located in the focused state. For example, the position where the light spot is located in the focused state can be the central area of the target focus pixel group 14. Refer to Figure 2As shown, a large portion of the light spot 15 is located in the area where the first focusing pixel 141 is located, and another portion of the light spot 15 is located in the area where the second focusing pixel 142 is located. The portion of the light spot 15 located in the area where the first focusing pixel 141 is located has a significantly larger light intensity because some of the light is not filtered. Compared with the difference in light intensity between the two portions of the light spot 15 in related technologies, the difference in light intensity is significantly larger in this application.

[0059] That is, some light spots 15 will enter the area without the color filter structure 121. The light entering this area will not be filtered, resulting in a significant enhancement of the light signal in the focusing pixel of that area. Consequently, the signal response difference between the two focusing pixels will be greater, the separation ratio will increase, and thus the sensitivity of autofocus will be improved. Furthermore, since some areas still have the target color filter structure 1211, the uniformity of pixel 111 is guaranteed, and the image quality will not be affected.

[0060] In one possible implementation, the target focusing pixel group 14 may include a 2*2 pixel structure, a 2*1 pixel structure, a dual-pixel structure, or a half-shielded pixel structure. The target focusing pixel group includes a first focusing pixel and a second focusing pixel, and focusing is achieved by the difference in the response of the first focusing pixel and the second focusing pixel to the light signal. The 2*2 pixel structure can also be referred to as a 2*2 quad-phase detection (QPD) pixel structure, the 2*1 pixel structure as a 2*1 PDAF pixel structure, the dual-pixel structure as a Dual PD pixel structure, and the half-shielded pixel structure as a Halfshield PDAF pixel structure.

[0061] When the target focusing pixel group 14 has a 2*2 pixel structure, the target focusing pixel group 14 includes 4 sequentially adjacent pixels 111, the first focusing pixel 141 includes two adjacent pixels 111, and the second focusing pixel 142 includes another two adjacent pixels 111.

[0062] Specifically, the four pixels 111 can be divided vertically, with the top two pixels 111 designated as the first focusing pixel 141 and the bottom two pixels 111 designated as the second focusing pixel 142. Alternatively, the four pixels 111 can be divided horizontally, with the left two pixels 111 designated as the first focusing pixel 141 and the right two pixels 111 designated as the second focusing pixel 142. (Reference) Figure 3 As shown, this is a schematic diagram of a target focusing pixel group 14 provided in an embodiment of this application. (a) shows four pixels 111, with the two pixels 111 on the left serving as the first focusing pixels 141 and the two pixels 111 on the right serving as the second focusing pixels 142.

[0063] Furthermore, when calculating the response difference between two focus pixels, it does not specifically designate which two are the first focus pixel 141 and which two are the second focus pixel 142. Instead, it can calculate both sets of focus images obtained by dividing the image vertically and horizontally. That is, if there is no response difference for the focus pixels obtained by dividing the image vertically, the response difference for the focus pixels obtained by dividing the image horizontally will be used as the basis for focusing.

[0064] In addition, regardless of the structure of the target focusing pixel group 14, in order to compare the response differences under the same standard, the first focusing pixel 141 and the second focusing pixel 142 can be set to the same color, that is, the target color filter structure 1211 above them only allows light of the same color to pass through, such as red.

[0065] In a 2x2 pixel arrangement, all pixels 111 in pixel array layer 11 can be used to form target focusing pixel group 14, meaning that in pixel array layer 11, every four pixels 111 correspond to the same lens 131. Figure 3 In the diagram, the large circle represents the boundary of the target lens 1311, and the small circle represents the boundary of the light spot 15.

[0066] When the target focusing pixel group 14 has a 2*1 pixel structure, the target focusing pixel group 14 may include two adjacent pixels 111, and the two pixels 111 may be used as the first focusing pixel 141 and the second focusing pixel 142 respectively.

[0067] refer to Figure 3 As shown in (b), two pixels 111 are shown. The left pixel 111 serves as the first focus pixel 141, and the right pixel 111 serves as the second focus pixel 142. That is, one pixel 111 can serve as one focus pixel.

[0068] In this structure, for the other pixels 111 in the pixel array layer 11, one pixel 111 can correspond to one lens 131. Since two focusing pixels correspond to one lens 131, the focusing pixels are specially designed pixels 111, meaning that not all pixels 111 can be used as focusing pixels.

[0069] When the target focusing pixel group 14 is a dual-pixel structure, the target focusing pixel group 14 may include one pixel 111, and the two halves of the pixel 111 serve as the first focusing pixel 141 and the second focusing pixel 142, respectively.

[0070] refer to Figure 3As shown in (c), a pixel 111 is illustrated, with its left half serving as the first focusing pixel 141 and its right half serving as the second focusing pixel 142. Thus, response differences can be obtained using only one pixel 111. In this structure, each pixel 111 in the pixel array layer 11 can serve as a focusing pixel group, with each pixel 111 corresponding to a lens 131.

[0071] When the target focusing pixel group 14 is a semi-occluded pixel structure, the target pixel group 111 includes two pixels 111, and the occluded areas of the two pixels 111 are different. The two pixels 111 serve as the first focusing pixel 141 and the second focusing pixel 142, respectively.

[0072] In other words, both pixels 111 have partially occluded areas, but the occluded areas are in different locations; they can be understood as being occluded in opposite directions. For example, if the occluded area of ​​one pixel 111 is the left half, then the occluded area of ​​the other pixel 111 is the right half. The unoccluded areas of each pixel can serve as focus pixels. Furthermore, these two pixels 111 can be adjacent or non-adjacent; when they are not adjacent, they are generally close to each other.

[0073] refer to Figure 3 As shown in (d), two pixels 111 are illustrated. The lower pixel 111 obscures the right half, and the unobscured portion serves as the first focusing pixel 141. The upper pixel 111 obscures the left half, and the unobscured portion serves as the second focusing pixel 142. In this structure, not every pixel 111 in the pixel array layer 11 can serve as a focusing pixel. The focusing pixel is a special pixel structure, and multiple groups of focusing pixels can be distributed in multiple locations throughout the image sensor.

[0074] In one possible implementation, when light is obliquely incident on the target lens 1311, the light has a stacking component in the stacking direction and a target component in the target direction; the target direction is a first direction or a second direction, and the first direction and the second direction are perpendicular to each other with the stacking direction; in the target direction, the first length of the target color filter structure 1211 is less than the second length of the target focusing pixel group 14.

[0075] Specifically, the image sensor has a large number of lenses 131 on its entire plane. When light is incident on the lenses 131, for lenses 131 located in the central region, the light can be considered to be incident perpendicularly, while for lenses 131 located in the edge region, the light is incident obliquely. When light is incident obliquely on the lenses 131, the light not only has a component along the stacking direction (e.g., the z-axis direction), i.e., the stacking component, but also a component along a first direction (e.g., the x-direction) or a second direction (e.g., the y-direction), i.e., the target component. The first direction and the second direction are perpendicular to each other with respect to the stacking direction.

[0076] When the target direction is the first direction, the first length of the target color filter structure 1211 in the first direction is less than the second length of the target focusing pixel group 14 in the same direction. Specifically, when the light has a light component in the first direction, it means that when the light is out of focus, it will move along the first direction, and the light spot 15 will also move. In order to ensure that some of the light spots 15 are not filtered, the target color filter structure 1211 needs to be set with a smaller length in the direction of movement of the light spot 15 (i.e., the first direction). That is, the first length of the target color filter structure 1211 in the first direction is smaller and less than the second length of the target focusing pixel group 14.

[0077] refer to Figure 4 As shown in Figure (a), a three-dimensional schematic diagram of light incident on the image sensor is presented. The light is incident on the image sensor 10 from top to bottom, showing that some light rays are incident perpendicularly. The angle of incidence between the light rays and the surface of the image sensor 10 increases as they move outward from the center, resulting in a more oblique incidence. Based on the incident direction of the light, the size of the target color filter structure 1211 can be designed. That is, along the first direction, the target color filter structure 1211 cannot completely cover the target focusing pixel group 14.

[0078] Along the first direction, the area near the two side boundaries of the image sensor 10 is referred to as the first boundary region 101. The design of the pixel 111 focusing pixel group and the target color filter structure 1211 in this region can be such that the first length of the target color filter structure 1211 in the first direction is smaller than the second length of the target focusing pixel group 14 in the same direction.

[0079] Figure 4 Image (b) shows a top view of the target focusing pixel group 14 and the target color filter structure 1211 located within the first boundary region 101. The light spot 15 moves laterally. The two pixels 111 on the left serve as the first focusing pixels 141, and the two pixels 111 on the right serve as the second focusing pixels 142. The length of the target color filter structure 1211 in the lateral direction is less than the length of the target focusing pixel group 14 in the lateral direction. Furthermore, to more accurately determine the area, shape, and position of the target color filter structure 1211, relevant calculations can be performed based on optical simulation.

[0080] Similarly, when the target direction is the second direction, the first length of the target color filter structure 1211 in the second direction is less than the second length of the target focusing pixel group 14 in that direction. Specifically, when the light has a light component in the second direction, it means that when the light is out of focus, it will move along the second direction, and the light spot 15 will also move. In order to ensure that some of the light spot 15 is not filtered, the target color filter structure 1211 needs to be set with a smaller length in the direction of movement of the light spot 15 (i.e., the second direction). That is, the first length of the target color filter structure 1211 in the second direction is smaller and less than the second length of the target focusing pixel group 14.

[0081] refer to Figure 5 As shown in Figure (a), a three-dimensional schematic diagram of light incident on the image sensor is presented. The light is incident on the image sensor 10 from top to bottom, showing that some light rays are incident perpendicularly. The angle of incidence between the light rays and the surface of the image sensor 10 increases as they move outward from the center, resulting in a more oblique incidence. Based on the incident direction of the light, the size of the target color filter structure 1211 can be designed. That is, along the second direction, the target color filter structure 1211 cannot completely cover the target focusing pixel group 14.

[0082] Along the second direction, the region near the two side boundaries of the image sensor 10 is referred to as the second boundary region 102. The design of the pixel 111 focusing pixel group and the target color filter structure 1211 in this region can be such that the first length of the target color filter structure 1211 in the second direction is smaller than the second length of the target focusing pixel group 14 in the same direction.

[0083] Figure 5 (b) shows a top view of the target focusing pixel group 14 and the target color filter structure 1211 located within the first boundary region 101. The light spot 15 moves along the longitudinal direction. The two upper pixels 111 serve as the first focusing pixel 141, and the two lower pixels 111 serve as the second focusing pixel 142. The length of the target color filter structure 1211 in the longitudinal direction is less than the length of the target focusing pixel group 14 in the lateral direction.

[0084] Therefore, when light is obliquely incident on lens 131, the light spot 15 will move in the direction (i.e. the target direction) along the light incident direction. By designing the color filter structure 121 to be shorter in this direction, the shape and position of the color filter structure 121 can be precisely designed, which can further improve the response difference and further improve the separation ratio.

[0085] In one possible implementation, the target direction is a first direction and a second direction. In most cases, light has three light components: a stacking component along the stacking direction, a first component along the first direction, and a second component along the second direction. For example, for the four corner regions of an image sensor, the light incident on these regions has three light components.

[0086] In the target direction, the first length of the target color filter structure 1211 is less than or equal to the second length of the target focusing pixel group 14. When the first length is less than the second length, that is, the size of the target color filter structure 1211 is relatively small in both the first and second directions, i.e., the target color filter structure 1211 is smaller than the size of the target focusing pixel group 14 in both directions.

[0087] refer to Figure 6 As shown in (a), a rectangular target color filter structure 1211 is illustrated. The sides of the target color filter structure 1211 are parallel to the sides of the target focusing pixel group 14. The dimensions of the target color filter structure 1211 in both the horizontal and vertical directions are smaller than the dimensions of the target focusing pixel group 14, and the boundaries of the target color filter structure 1211 are completely within the boundaries of the target focusing pixel group 14. This design structure can be positioned, for example, near the diagonal of the image sensor, such as in a corner region.

[0088] The first length can also be equal to the second length. In this case, it can be understood that the rectangular target color filter structure 1211 has been rotated, and the first length is the length of the diagonal of the rectangle. (Refer to...) Figure 6 As shown in (b) in the diagram. In this way, when the light spot 15 moves diagonally along the target focusing pixel group 14, it can ensure that as much light as possible falls into the transparent area, that is, it will not be filtered, further increasing the response difference between the two focusing pixels and further improving the separation ratio.

[0089] In one possible implementation, the projected shape of the target color filter structure 1211 in the stacking direction may include a rectangle, a circle, or a cross. (See reference) Figure 6 As shown, the projected shape of the target color filter structure 1211 in (a), (d) and (e) is a rectangle, the projected shape in (b) and (c) is a rotated rectangle, and (f) is a cross shape.

[0090] refer to Figure 7 The image sensor is shown in a top view when the target focusing pixel group 14 has a 2*1 pixel structure. In (a), the horizontal dimension of the target color filter structure 1211 is smaller than the horizontal dimension of the target focusing pixel group 14, and the target color filter structure 1211 is a vertically elongated strip shape. In (b), the target color filter structure 1211 is a rotated rectangular structure. (Reference) Figure 8The image shown is a top view of the target focusing pixel group 14 when it is a semi-occluded pixel structure. A vertical strip-shaped target color filter structure 1211 is set in both focusing pixels, and the two target color filter structures 1211 are the same size.

[0091] In one possible implementation, the first projected area of ​​the target color filter structure 1211 can be greater than or equal to the area of ​​the light spot generated by the focused light from the target lens. That is, the size of the target color filter structure 1211 is not less than the size of the light spot 15. (Reference) Figure 9 As shown, the target color filter structure 1211 is a square structure, that is, its length is equal to the diameter of the light spot 15.

[0092] In the stacking direction, the projection of the target color filter structure 1211 completely covers the target projection of the light spot 15, and the target projection is the projection of the light spot 15 when in focus.

[0093] In other words, the projection of the light spot 15 in the stacking direction during focusing can be denoted as the target projection. For example... Figure 9 As shown, the target color filter structure 1211 completely covers the light spot 15, and their centers coincide. Since the incident direction of light on the lens 131 located at different positions is different, for example, the light will be incident normally on the lens 131 near the center and obliquely on the lens 131 near the edge, the light spot may not necessarily fall on the exact center of the target focusing pixel group 14 during focusing. That is, the center of the target projection may not coincide with the center of the target focusing pixel group 14.

[0094] For example, the center of the target projection may coincide with the center of the target focusing pixel group 14, which means that when in focus mode, light is incident on the center position of the target focusing pixel group 14. Of course, the center of the target projection may not coincide with the center of the target focusing pixel group 14, which means that when in focus mode, light is not incident on the center position of the target focusing pixel group 14.

[0095] In this way, by setting the target color filter structure 1211 at the location of the light spot 15 in the focusing state, that is, there is no blank area at this location, it can be ensured that when the focusing is completed, the light spot 15 can completely pass through the target color filter structure 1211, ensuring that the light entering the focusing pixel is a single color, achieving normal imaging, without affecting the color correlation performance of the pixel 111, and the uniformity of the pixel 111 is better, ensuring higher image quality.

[0096] In one possible implementation, the center of the target focusing pixel group 14 may or may not coincide with the center of the target color filter structure 1211. When their centers coincide, the target color filter structure 1211 is evenly distributed in the two regions where the two focusing pixels are located, which simplifies the manufacturing process and reduces manufacturing costs. When their centers do not coincide, the area of ​​the target color filter structure 1211 located in the first focusing pixel 141 will be larger (or smaller), and the area of ​​the target color filter structure 1211 located in the second focusing pixel 142 will be smaller (or larger), thus allowing for customized design based on actual needs.

[0097] This application provides an image sensor comprising a pixel array layer, a color filter layer, and a lens array layer stacked sequentially along a stacking direction. The pixel array layer includes at least one target focusing pixel group; the lens array layer includes at least one target lens; and the color filter layer includes at least one target color filter structure, with each target color filter structure corresponding to a target lens. In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group. Thus, during focusing, since the target color filter structure does not completely cover the area where the target focusing pixel group is located, when the image is out of focus, light will obliquely enter the target lens, and the resulting light spot will deviate from its position when in focus. Some light spots will enter areas without a color filter structure. Light entering these areas will not be filtered, resulting in a significant increase in the light signal in these areas. Consequently, a large difference in signal response will appear in the target focusing pixel group, increasing the separation ratio and thus improving the sensitivity of autofocus. Furthermore, since some areas still have a target color filter structure, pixel uniformity is ensured, and image quality is not affected.

[0098] This application also provides a method for fabricating an image sensor, referring to... Figure 10 The diagram shown is a flowchart illustrating a method for fabricating an image sensor according to an embodiment of this application, which specifically includes the following steps.

[0099] S101, forming pixel array layer 11.

[0100] The pixel array layer 11 includes at least one target focusing pixel group 14.

[0101] S102, a color filter layer 12 is formed on one side of the pixel array layer 11.

[0102] The color filter layer 12 includes at least one target color filter structure 1211.

[0103] S103, a lens array layer 13 is formed on the side of the color filter layer 12 away from the pixel array layer 11.

[0104] The lens array layer 13 includes at least one target lens 1311, which corresponds one-to-one with the target color filter structure 1211.

[0105] In the stacking direction, the first projected area of ​​the target color filter structure 1211 is smaller than the second projected area of ​​the target focusing pixel group 14.

[0106] In one possible implementation, a color filter layer 12 is formed on one side of the pixel array layer 11. Specifically, a color filter material layer is formed on one side of the pixel array layer 11; the color filter material layer is photolithographically processed by a preset mask pattern to obtain the color filter layer 12.

[0107] In other words, a color filter material layer can be deposited on the surface of the pixel array layer 11, a preset mask pattern can be placed on top of the color filter material layer, and photolithography can be performed to obtain a color filter layer 12 with the corresponding pattern. During the photolithography process, photoresist can be coated on top of the color filter material layer, the preset mask pattern can be transferred onto the photoresist, and then the color filter material layer can be etched using the photoresist as a mask to obtain the color filter layer 12, thereby improving the etching accuracy and etching efficiency of the color filter layer 12.

[0108] Specifically, the preset mask pattern may include at least one target mask region, which may include a light-shielding area and a light-transmitting area. During the photolithography process, the light-shielding area is used to form a target color filter structure. The target mask region may be a mask region located above the target focusing pixel group 14. The light-shielding area of ​​the target mask region is used to provide a shielding effect to prevent light from illuminating the color filter layer 12 below it, while the light-transmitting area is used to allow light to illuminate the color filter layer 12 below it. Through the material difference between the illuminated color filter layer 12 and the unilluminated color filter layer 12, the target color filter structure 1211 can be formed on the color filter layer 12 by development.

[0109] In practical applications, the photoresist used can be positive photoresist or negative photoresist. When using positive photoresist, the color filter layer 12 located below the light-shielding area is retained to form the target color filter structure 1211. At this time, the pattern of the target mask area is the same as the pattern of the color filter layer. When using negative photoresist, the color filter layer 12 located below the light-shielding area is removed, and the color filter layer 12 located below the light-transmitting area is retained to form the target color filter structure 1211. At this time, the pattern of the target mask area is opposite to the pattern of the color filter layer.

[0110] This application provides a method for fabricating an image sensor. During the focusing process, because the target color filter structure does not completely cover the area where the target focusing pixel group is located, when the image is out of focus, light will obliquely enter the target lens, and the resulting light spot will deviate from its position when in focus. Some light spots will enter the area where the color filter structure is not set. The light entering this area will not be filtered, resulting in a significant increase in the light signal in this area. Consequently, a large difference in signal response will appear in the target focusing pixel group, and the separation ratio will increase, thereby improving the sensitivity of autofocus. Furthermore, since the target color filter structure is still set in some areas, pixel uniformity is ensured, and image quality is not affected.

[0111] This application also provides an electronic device, including an image sensor. The electronic device can be, for example, a mobile phone, tablet, computer, or other device that needs to acquire images, and will not be described in detail further. This electronic device can achieve a high resolution, improve autofocus sensitivity, and does not affect image quality.

[0112] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the method embodiments are basically similar to the apparatus embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the apparatus embodiments.

[0113] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. An image sensor, characterized in that, include: The pixel array layer, color filter layer, and lens array layer are stacked sequentially along the stacking direction; The pixel array layer includes at least one target focusing pixel group; the lens array layer includes at least one target lens; The color filter layer includes at least one target color filter structure, which corresponds one-to-one with the target lens. In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group.

2. The image sensor according to claim 1, characterized in that, When light is obliquely incident on the target lens, the light has a stacking component in the stacking direction and a target component in the target direction; The target direction is either a first direction or a second direction, and the first direction and the second direction are perpendicular to each other with the stacking direction. In the target direction, the first length of the target color filter structure is less than the second length of the target focusing pixel group.

3. The image sensor according to claim 2, characterized in that, The target direction is the first direction and the second direction; In the target direction, the first length of the target color filter structure is less than or equal to the second length of the target focusing pixel group.

4. The image sensor according to claim 1, characterized in that, The first projected area of ​​the target color filter structure is greater than or equal to the area of ​​the light spot generated by the focused light of the target lens; In the stacking direction, the projection of the target color filter structure completely covers the target projection of the light spot, which is the projection of the light spot when in focus.

5. The image sensor according to claim 1, characterized in that, The center of the target focusing pixel group may or may not coincide with the center of the target color filter structure.

6. The image sensor according to claim 1, characterized in that, The target focusing pixel group includes a 2*2 pixel structure, a 2*1 pixel structure, a dual-pixel structure, or a semi-masked pixel structure; the target focusing pixel group includes a first focusing pixel and a second focusing pixel, and focusing is achieved by the difference in the response of the first focusing pixel and the second focusing pixel to light signals.

7. The image sensor according to claim 1, characterized in that, In the stacking direction, the projected shape of the target color filter structure includes a rectangle, a circle, or a cross.

8. A method for fabricating an image sensor, characterized in that, include: A pixel array layer is formed, the pixel array layer including at least one target focusing pixel group; A color filter layer is formed on one side of the pixel array layer, the color filter layer including at least one target color filter structure; A lens array layer is formed on the side of the color filter layer away from the pixel array layer, and the lens array layer includes at least one target lens; The target lens corresponds one-to-one with the target color filter structure; In the stacking direction, the first projected area of ​​the target color filter structure is smaller than the second projected area of ​​the target focusing pixel group.

9. The method for fabricating an image sensor according to claim 8, characterized in that, A color filter layer is formed on one side of the pixel array layer, including: A color filter material layer is formed on one side of the pixel array layer; The color filter material layer is photolithographically processed by a preset mask pattern to obtain the color filter layer; the preset mask pattern includes at least one target mask area, the target mask area includes a light-shielding area and a light-transmitting area, and the target color filter structure is formed by the light-shielding area during the photolithography process.

10. An electronic device, characterized in that, Including the image sensor as described in any one of claims 1-7.

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