Image sensor and electronic device thereof

Abstract

The utility model provides an image sensor and an electronic device thereof, the image sensor comprises a pixel array, the pixel array comprises a plurality of pixel units arranged in an array, one part of the plurality of pixel units is image pixels, the other part of the plurality of pixel units is focusing pixels, the focusing pixels comprise photosensitive elements, micro lenses, metal shielding structures and optical anti-reflection layers, wherein the metal shielding structure is located between the micro lens and the photosensitive element to shield part of incident light entering the photosensitive element, the optical anti-reflection layer covers the upper surface of the metal shielding structure, and the photosensitive element is located below the metal shielding structure. According to the utility model, on the premise that the function of the focusing pixel is not influenced, the reflection of the surface of the metal layer is reduced through the optical anti-reflection layer, and the crosstalk near the focusing pixel is reduced, thereby facilitating the improvement of the final image quality.

Description

Technical Field

[0001] This utility model belongs to the field of optical and sensing technology, and relates to an image sensor and its electronic device. Background Technology

[0002] CMOS image sensors (CIS) are already ubiquitous in our daily lives, from smartphones to cars, security cameras, robots, and AR / VR entertainment devices. This trend is driven by strong demand for smart, connected, and autonomous consumer products as we transition to the Internet of Things (IoT) era. Thanks to advancements in manufacturing processes, CIS has evolved from front-illuminated to back-illuminated structures, significantly improving photosensitivity with smaller pixels, reducing optical crosstalk, and enhancing the final image quality.

[0003] On-chip autofocus technology on CMOS image sensors has also been widely used in consumer electronics. Phase detection autofocus (PDAF) is characterized by its fast focusing speed and high accuracy, making it the mainstream autofocus solution. To achieve on-chip phase detection autofocus, special pixel optical structures are typically designed, mainly including metal semi-obscured types, 2×1 pixel microlens types, and 2×2 pixel microlens types. Using these structures, the pixels acquire sensitivity to the angle of incident light, thus enabling phase detection. For focusing pixels using metal semi-obscured types, the metal shielding structure covers the pixels, and metal has high reflectivity. This reflected light, after passing through the organic planarization layer and microlens, can be reflected again and enter neighboring pixels, easily causing crosstalk and leading to abnormal pixel signals near the focusing pixel.

[0004] Therefore, how to reduce crosstalk near the focusing pixel without affecting the focusing pixel function has become an important technical problem that needs to be solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Utility Model Content

[0006] In view of the shortcomings of the prior art described above, the purpose of this utility model is to provide an image sensor and its electronic device to solve the problem of large crosstalk near the focus pixel in the prior art.

[0007] To achieve the above and other related objectives, this utility model provides an image sensor, including a pixel array. The pixel array includes multiple pixel units arranged in an array, a portion of which are image pixels and another portion are focus pixels. The focus pixels include:

[0008] Photosensitive element;

[0009] Microlenses are located above the photosensitive element;

[0010] A metal shielding structure is located between the microlens and the photosensitive element to partially block incident light from reaching the photosensitive element;

[0011] An optical antireflective layer is applied to the upper surface of the metal shielding structure.

[0012] Optionally, the pixel array includes a metal grid structure, and the metal occlusion structure is located on the same layer as the metal grid structure.

[0013] Optionally, the optical antireflective layer also covers the upper surface of the metal grid structure; and / or, the top surface of the metal shielding structure is flush with or lower than the top surface of the metal grid structure.

[0014] Optionally, each pixel unit is provided with a color filter, and the color filter and the metal shielding structure are configured in the following ways:

[0015] The color filter is located on the same layer as the metal shielding structure, wherein there is a gap between the color filters of two adjacent pixel units; or, the color filters of two adjacent pixel units are connected above the metal grid structure or above the metal shielding structure; or, the color filter is located in a layer above the metal shielding structure.

[0016] Optionally, at least one of the metal shielding structure, the metal grid structure, and the microlens is offset relative to the corresponding photosensitive element toward the center of the pixel array. When the pixel unit is provided with a color filter, at least one of the metal shielding structure, the metal grid structure, the microlens, and the color filter is offset relative to the corresponding photosensitive element toward the center of the pixel array.

[0017] Optionally, each offset structure has a corresponding offset distance, and the offset distance corresponding to each type of offset structure increases from the center of the pixel array toward the edge of the pixel array.

[0018] Optionally, the pixel array includes at least two types of shared pixel structures for acquiring focus information, each of the shared pixel structures including at least two focus pixels, and at least two of the shared pixel structures of the same type have different proportions of incident light blocking.

[0019] Optionally, the shared pixel structure includes four focusing pixels arranged in a 2×2 array, wherein the shared pixel structure includes a staggered occlusion pixel structure, wherein the four metal occlusion structures corresponding to the four focusing pixels in the staggered occlusion pixel structure have the same phase and different occlusion ratios; and / or, the occlusion ratio of the metal occlusion structure corresponding to a single focusing pixel in the shared pixel structure to the incident light is between 20% and 80%.

[0020] Optionally, the optical antireflection layer includes at least one of a metal layer and a dielectric layer.

[0021] Optionally, the optical antireflection layer includes at least one interference extinction unit, which reduces the reflection of light incident on the metal light-shielding structure.

[0022] Optionally, the interference extinction unit includes a stacked metal layer and a dielectric layer; and / or, an interference auxiliary layer is further provided between the interference extinction unit and the metal shielding structure.

[0023] Optionally, when the interference extinction unit comprises a stacked metal layer and a dielectric layer, the configuration of the interference extinction unit includes:

[0024] The surface of the metal layer is further provided with a surface transition layer, and / or the thickness of the metal layer is less than the thickness of the dielectric layer; and / or the thickness of the metal layer is between 5nm and 15nm.

[0025] When an interference auxiliary layer is provided between the interference extinction unit and the metal shielding structure, the interference auxiliary layer is made of the same material as the metal layer in the interference extinction unit and / or the metal material of the interference auxiliary layer is different from that of the metal shielding structure.

[0026] Optionally, the optical anti-reflection layer covers the entire upper surface of the metal shielding structure, or the upper surface of the portion of the metal shielding structure near the center region of the focusing pixel is not covered by the optical anti-reflection layer; and / or, the upper surface and side surfaces of the combined structure consisting of the metal shielding structure and the optical anti-reflection layer are covered by a dielectric layer; and / or, the color filter corresponding to the focusing pixel is a green color filter.

[0027] This invention also provides an electronic device that includes an image sensor as described in any of the above embodiments.

[0028] As described above, the image sensor of this invention includes a pixel array, which comprises multiple pixel units arranged in an array. A portion of these pixel units are image pixels, and another portion are focus pixels. Each focus pixel includes a photosensitive element, a microlens, a metal shielding structure, and an optical anti-reflection layer. The metal shielding structure is located between the microlens and the photosensitive element to block some of the incident light reaching the photosensitive element. The optical anti-reflection layer covers the upper surface of the metal shielding structure, and the photosensitive element is located below the metal shielding structure. This invention can reduce the reflection from the metal surface through the optical anti-reflection layer without affecting the function of the focus pixels, thereby reducing crosstalk near the focus pixels and contributing to improved final image quality. Attached Figure Description

[0029] Figure 1 The diagram shown is a partial cross-sectional view of the image sensor of this invention in one embodiment.

[0030] Figure 2 The diagram shown is a partial cross-sectional view of the image sensor of this invention in another embodiment.

[0031] Figure 3 The diagram shown is a partial cross-sectional view of the image sensor of this utility model in another embodiment.

[0032] Figure 4 The diagram shown is a partial cross-sectional view of the image sensor of this utility model in another embodiment.

[0033] Figure 5 The diagram shows a cross-sectional view of a pixel array employing a high-metal grid (HMG) structure.

[0034] Figure 6 The diagram shows a cross-sectional view of a pixel array employing a low-metal grid (LMG) structure.

[0035] Explanation of reference numerals in the attached figures

[0036] 101 Semiconductor Substrate

[0037] 102 Anti-reflective layer

[0038] 103 Metal Grid

[0039] 104 silicon oxide layer

[0040] 105 Color Filter Layers

[0041] 106 Flattening layer

[0042] 107 microlenses

[0043] 108 Metal shielding structure

[0044] 200 green image pixels

[0045] 300 blue image pixels

[0046] 400 focus pixels

[0047] 401 Microlens

[0048] 402 Metal shielding structure

[0049] 403 Optical Antireflective Layer

[0050] 500 semiconductor substrate

[0051] 600 Metal Grid Structure

[0052] 700 dielectric layer

[0053] 800 color filter

[0054] 900 anti-reflective layer

[0055] 1000 leveling layer Detailed Implementation

[0056] To reduce reflections on the metal layer surface and minimize crosstalk near the focusing pixel without affecting its function, this invention improves the pixel structure design, particularly the focusing pixel structure design, to achieve a low-crosstalk metal semi-occluded phase detection focusing pixel. Specifically, by adding an optical anti-reflection layer to the metal occlusion structure, the reflections on the metal layer surface can be reduced, thereby minimizing crosstalk near the focusing pixel, without affecting its function.

[0057] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model.

[0058] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0059] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0060] In the detailed description of the embodiments of this utility model, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of this utility model. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0061] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0062] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0063] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0064] The image sensor of this invention includes a pixel array, which comprises multiple pixel units arranged in an array. A portion of the multiple pixel units are image pixels, and another portion are focus pixels. The focus pixels can realize on-chip phase detection autofocus.

[0065] As an example, the pixel array uses a Bayer array, which typically employs a 2×2 repeating pattern, with green (G) pixels making up half and red (R) and blue (B) pixels each making up a quarter. This arrangement takes into account the human eye's higher sensitivity to green light, thus the number of green pixels is twice that of red and blue pixels. Of course, other arrangements in existing technologies, such as the CMMY array arrangement, can also be used, depending on the actual needs.

[0066] In some implementations, the high density distribution of green pixels makes them play a dominant role in the brightness information of the image. In some embodiments of this invention, the color filter corresponding to the focus pixel is preferably a green color filter.

[0067] It should be noted that in some cases, it is not ruled out that the color filter corresponding to the focus pixel may be a red or blue color filter.

[0068] Specifically, since the focusing pixels disrupt the Bayer array to some extent, the proportion of image pixels in the pixel array is relatively high, while the proportion of focusing pixels is relatively low. For example, in some embodiments of this utility model, the proportion of focusing pixels can be 1.5%-12%, and further can be 3%-6%.

[0069] For example, please refer to Figure 1 The image sensor of this utility model is shown as a partial structural cross-sectional view in one embodiment, which passes through two green image pixels 200, two blue image pixels 300 and one focus pixel 400.

[0070] Specifically, the focusing pixel 400 includes a photosensitive element (not shown), a microlens 401, a metal shielding structure 402, and an optical antireflective layer 403. The photosensitive element is located in a semiconductor substrate 500 and can be a photodiode (PD). The metal shielding structure 402 is located between the microlens 401 and the photosensitive element to block a portion of the incident light incident on the photosensitive element. For example, the metal shielding structure 402 blocks half of the incident light incident on the photosensitive element. The image pixel has a similar structure to the focusing pixel 400, except that it does not have the metal shielding structure 402.

[0071] As an example, the semiconductor substrate 500 may be a silicon substrate or other suitable substrate, and each of the image pixels and each of the focus pixels has its own corresponding photosensitive element in the conductor substrate 500. Adjacent photosensitive elements may be isolated from each other by an isolation structure.

[0072] Specifically, in Figure 1 From a certain perspective, the metal shielding structure 402 is located in the right region of the focusing pixel 400, thereby blocking light entering the right side of the photosensitive element from the microlens. In other regions of the pixel structure, the metal shielding structure 402 may also be located in the left region of the focusing pixel 400, thereby blocking light entering the left side of the photosensitive element from the microlens.

[0073] Specifically, the optical antireflection layer 403 is provided on the upper surface of the metal shielding structure 402, which can suppress the reflection of light by the metal shielding structure 402, thereby reducing crosstalk caused by metal reflection, reducing crosstalk near the focus pixel, and improving the abnormal pixel signal near the focus pixel.

[0074] Specifically, the optical antireflection layer 403 utilizes the principle of light interference, that is, when light is incident on the interface of different media, reflection and refraction will occur. When light is incident on the optical antireflection layer 403, it will be reflected on the upper and lower surfaces of the film, forming two beams of reflected light. By designing the thickness and refractive index of the film layer, the phase difference between the two beams of reflected light is π (i.e., the optical path difference is λ / 2), so that the two beams of reflected light can cancel each other out, thereby reducing the reflected light.

[0075] As an example, the optical antireflection layer 403 can adopt a single-layer film structure or a multi-layer film structure. In the latter case, by stacking thin films with different refractive indices and thicknesses, low reflection can be achieved in a wider wavelength range. By accurately calculating and optimizing the thickness and refractive index of each thin film, the best antireflection effect can be achieved in a specific spectral range.

[0076] As an example, the total thickness of the optical antireflection layer 403 is less than 200 nm. When the optical antireflection layer 403 adopts a multilayer film structure, the thickness of each film layer in the multilayer film structure is 1 nm to 100 nm.

[0077] As an example, the optical antireflection layer 403 includes at least one of a metal layer and a dielectric layer. The metal layer may be a titanium layer, a titanium nitride layer, or other suitable metal material layer, and the dielectric layer may be a silicon oxide layer, a silicon nitride layer, or other suitable dielectric material layer.

[0078] As an example, the optical antireflection layer 403 includes at least one interference extinction unit (not shown in the figure), which reduces the reflection of light incident on the metal light-shielding structure 402.

[0079] As an example, the interference extinction unit includes a stacked metal layer and a dielectric layer.

[0080] As an example, an interference auxiliary layer is also provided between the interference extinction unit and the metal shielding structure 402.

[0081] As an example, when the interference extinction unit includes a stacked metal layer and a dielectric layer, the configuration of the interference extinction unit includes at least one of the following three methods: that is, the surface of the metal layer is further provided with a surface transition layer, such as a material layer to prevent metal diffusion, such as a titanium nitride layer; and the thickness of the metal layer is less than the thickness of the dielectric layer, which is beneficial to the transmission and reflection of incident light to form interference light; and / or the thickness of the metal layer is between 5nm and 15nm, for example, the thickness of the metal layer can be 8nm, 10nm, 12nm, etc., which is beneficial to the transmission of incident light and interface reflection.

[0082] As an example, when an interference auxiliary layer is provided between the interference extinction unit and the metal shielding structure 402, the reduction of reflected light is further enhanced by the interference auxiliary layer disposed on the surface of the metal shielding structure. The interference auxiliary layer is made of the same material as the metal layer in the interference extinction unit. Further, the material of the interference auxiliary layer is different from the material of the metal shielding structure 402. For example, the metal layer in the interference extinction unit and the interference auxiliary layer are selected as titanium layers, and the metal shielding structure is selected as a tungsten layer.

[0083] In some embodiments, the interference extinction unit includes a stacked metal layer (such as a titanium layer or a gold layer) and a dielectric layer (such as a silicon oxide layer), wherein the metal layer is located on the side closer to the incident light. Further, an interference auxiliary layer is provided between the interference extinction unit and the metal shielding structure 402; that is, an interference auxiliary layer is provided between the optical antireflection layer 403 and the metal shielding structure 402. The interference auxiliary layer can be a metal layer, such as a titanium layer. In a specific example, the optical antireflection layer 403 is a stacked structure consisting of an interference auxiliary layer, a dielectric layer, and a metal layer sequentially between the metal shielding structure 402 and the incident light.

[0084] As an example, the optical antireflection layer 403 may be formed by vacuum evaporation, magnetron sputtering, chemical vapor deposition (CVD), sol-gel method or other suitable methods.

[0085] As an example, the pixel array includes a metal grid structure 600, which is mainly used for optical isolation, i.e., blocking light from entering adjacent photosensitive elements, thereby reducing optical crosstalk between pixels and ensuring that each pixel can accurately capture its corresponding light signal, thereby improving the contrast and sharpness of the image.

[0086] As an example, the metal shielding structure 402 and the metal grid structure 600 are located on the same layer and can be made of the same metal material. Being on the same layer can mean that the vertical projections of the metal shielding structure 402 and the metal grid structure 600 in a direction perpendicular to the surface of the photosensitive element have an overlapping area.

[0087] As an example, the top surface of the metal shielding structure 402 is flush with or lower than the top surface of the metal grid structure 600. When the top surface of the metal shielding structure 402 is flush with the top surface of the metal grid structure 600, or when the metal shielding structure 402 and the metal grid structure 600 are at the same height, the metal shielding structure 402 and the metal grid structure 600 can be manufactured simultaneously. However, when the top surface of the metal shielding structure 402 is lower than the top surface of the metal grid structure 600, or when the metal shielding structure 402 and the metal grid structure 600 are not at the same height, the metal shielding structure 402 and the metal grid structure 600 can be manufactured in stages, for example, the metal grid structure 600 can be manufactured first, and then the metal shielding structure 402 can be manufactured.

[0088] As an example, the optical antireflective layer 403 also covers the upper surface of the metal grid structure 600, which helps to reduce reflected light from the surface of the metal grid structure 600 from entering adjacent photosensitive elements.

[0089] As an example, the optical antireflection layer on the surface of the metal shielding structure 402 and the optical antireflection layer on the surface of the metal grid structure 600 can be formed simultaneously, and the optical antireflection layer 403 is compatible with existing metal grid structures.

[0090] As an example, the upper surface and side surfaces of the combined structure consisting of the metal shielding structure 402 and the optical antireflection layer 403 are covered by a dielectric layer 700, which may be, for example, a silicon oxide layer. Similarly, the upper surface and side surfaces of the metal grid structure 600, or the upper surface and side surfaces of the combined structure consisting of the metal grid structure 600 and the optical antireflection layer 403, are also covered by the dielectric layer 700. The dielectric layers corresponding to the metal shielding structure 402 and the optical antireflection layer 403, and the dielectric layer corresponding to the metal grid structure 600, can be formed using the same process.

[0091] As an example, each pixel unit is provided with a color filter 800. For instance, a green (G) pixel is provided with a green color filter, a red (R) pixel is provided with a red color filter, a blue (B) pixel is provided with a blue color filter, and the focusing pixel 400 is provided with a green color filter. The color filter 800 may use organic dyes to achieve light filtering of specific wavelengths, exhibiting good color selectivity and high transmittance.

[0092] As an example, the color filter 800 can be located on the same layer as the metal shielding structure 402, for example... Figure 3 The example shown.

[0093] As an example, there is a gap between the color filters of two adjacent pixel units, for example in Figure 3 In the embodiment shown, the metal shielding structure 402 and the metal grid structure 600 are wrapped by a thicker dielectric layer 700 after the optical antireflection layer 403 is attached. The top surface of the dielectric layer 700 is substantially the same as or slightly higher than the top surface of the color filter 800, and there is no longer any organic color filter material on the top surface of the dielectric layer 700.

[0094] As an example, an antireflection layer 900 is further provided between the semiconductor substrate 500 and the layer containing the metal lattice structure 600 to improve light transmittance. The antireflection layer 900 may be one or more thin films with a specific thickness and refractive index, thereby reducing the reflection loss of the semiconductor substrate 500.

[0095] As an example, a planarization layer 1000 is further provided between the layer containing the color filter 800 and the layer containing the microlens 401. The planarization layer 1000 provides a smooth surface, allowing light to pass through the color filter array more uniformly, reducing light scattering caused by surface unevenness, ensuring tighter optical coupling between the microlens array and the color filter array, and enabling more light to be focused onto the photosensitive element by the microlens, thereby improving the sensor's sensitivity. Furthermore, the planarization layer 1000 also protects the color filter array and provides stable mechanical support for the microlens array. The planarization layer 1000 can be made of organic or inorganic materials. Organic materials may include, for example, polydimethylsiloxane (PDMS) or polymethyl methacrylate (PMMA), while inorganic materials may include, for example, spin-on glass or silicon dioxide.

[0096] For example, please refer to Figure 2 The image sensor of this utility model is shown as a partial structural cross-sectional schematic diagram in another embodiment, and... Figure 1 The difference between the embodiments shown is that, Figure 2 In the illustrated embodiment, the color filters of two adjacent pixel units are connected above the metal grid structure 600 or the metal shielding structure 402. The dielectric layer 700 that encloses the metal shielding structure 402 and the metal grid structure 600 is relatively thin, and a thin layer of color filter material is also present above the dielectric layer 700.

[0097] It should be pointed out that, in Figure 1 and Figure 2 In the illustrated embodiment, the optical antireflection layer 403 covers the entire upper surface of the metal shielding structure 402; however, in some other embodiments, the optical antireflection layer 403 may not completely cover the entire upper surface of the metal shielding structure 402.

[0098] For example, please refer to Figure 3The image sensor of this invention is shown in a partial cross-sectional view in another embodiment. In this embodiment, the upper surface of the portion of the metal shielding structure 402 near the center region of the focusing pixel 400 is not covered by the optical anti-reflection layer 403. That is, the optical anti-reflection layer 403 only covers the surface of the metal shielding structure 402 in the edge region of the focusing pixel 400, and only eliminates reflected light from the edge region, which is more likely to cause crosstalk. Based on the above design, it is beneficial for light entering the corresponding pixel through the microlens 401 to enter the photosensitive area not blocked by the metal shielding structure 402, thereby improving the photosensitive performance of the focusing pixel and improving the focusing accuracy.

[0099] It should be pointed out that, in Figure 1 , Figure 2 , Figure 3 In the embodiments shown, the color filters 800 are all located on the same layer as the metal shielding structure 402. However, in some other embodiments, the color filters 800 may also be located in a layer above the metal shielding structure 402.

[0100] For example, please refer to Figure 4 The image sensor of this utility model is shown as a partial structural cross-sectional schematic diagram in another embodiment, wherein the color filter 800 is located in a layer above the metal shielding structure 402.

[0101] It should be pointed out that, in Figures 1 to 4 In the illustrated embodiment, the metal grid structure 600 is not provided on the outside of the metal shielding structure 402 because the metal shielding structure 402 can act as the metal grid structure 600 here. However, in some other embodiments, for example when the design height of the metal grid structure 600 is higher than the height of the metal shielding structure 402, the metal grid structure 600 may be additionally provided on the outside of the metal shielding structure 402.

[0102] As an example, at least one of the metal shielding structure 402, the metal grid structure 600, and the microlens 401 is offset relative to the corresponding photosensitive element toward the center of the pixel array. When the pixel unit is provided with the color filter 800, at least one of the metal shielding structure 402, the metal grid structure 600, the microlens 401, and the color filter 800 is offset relative to the corresponding photosensitive element toward the center of the pixel array. Different pupil correction amounts can be implemented in different areas of the pixel array to reduce the sensitivity degradation of the photosensitive element.

[0103] In a further example, each offset structure has a corresponding offset distance. From the center of the pixel array toward the edge of the pixel array, the offset distances corresponding to each type of offset structure show an increasing trend. For example, for the metal occlusion structure 402, it occludes half of the corresponding pixel area to achieve half-occlusion and obtain phase information. Taking a certain pixel row as an example, there are at least two focusing pixels in the row, with at least two metal occlusion structures. In this row, the occlusion area of ​​the metal occlusion structure located in the center area of ​​the pixel array is 50%. For the metal occlusion structure far from the center of the pixel array, its center is offset toward the center of the pixel array by an occlusion offset distance. For this offset distance, the further away the metal occlusion structure is from the center of the pixel array, the larger the corresponding offset distance. Here, the so-called increasing trend can be that each one gradually increases, or there are several consecutive metal occlusion structures with the same offset distance, but the overall trend is gradually increasing.

[0104] As an example, the pixel array includes at least two types of shared pixel structures for acquiring focus information, each of the shared pixel structures including at least two of the focus pixels, and at least two of the shared pixel structures of the same type having different proportions of incident light blocking.

[0105] Among these, at least two types of shared pixel structures can be shared pixel structures that acquire left phase information and shared pixel structures that acquire right phase information, or they can be shared pixel structures that acquire upper phase information and shared pixel structures that acquire lower phase information, or they can be shared pixel structures that acquire left phase information, shared pixel structures that acquire right phase information, shared pixel structures that acquire upper phase information, and shared pixel structures that acquire lower phase information, thereby enabling phase-detection autofocus in different directions. Specifically, due to the light angle sensitivity, CIS with PDAF function has higher requirements for the matching degree of the lens's principal ray angle. In addition, in fields such as digital camera applications, a CIS usually needs to be compatible with multiple lenses. These lenses have a large span of principal ray angles, which can reach or even exceed 10° at the same image height, and the aperture adjustment range of the lenses is also wide. Among the shared pixel structures of the same type, there are at least two shared pixel structures with different incident light blocking ratios, which can achieve greater principal ray angle compatibility without increasing the focus point density, reduce the difficulty of algorithm correction, and improve image quality.

[0106] As an example, the shared pixel structure includes four focusing pixels arranged in a 2×2 array. The shared pixel structure includes a staggered occlusion pixel structure. In the staggered occlusion pixel structure, the four metal occlusion structures corresponding to the four focusing pixels have the same phase but different occlusion ratios. For example, in one example, the occlusion ratios of the four metal occlusion structures corresponding to the four focusing pixels are all different. It can be that the occlusion ratios of the metal occlusion structures corresponding to the upper left focusing pixel, upper right focusing pixel, lower left focusing pixel, and lower right focusing pixel increase sequentially to the incident light.

[0107] As an example, the metal blocking structure corresponding to a single focusing pixel blocks the incident light by a proportion between 20% and 80%, such as 20%, 30%, 40%, 50%, 60%, or 80%.

[0108] As an example, the pixel array forms rows and columns corresponding to the photosensitive elements. The occlusion ratio of the metal occlusion structure increases in the row direction and reaches 50% at the center of the pixel array, or the occlusion ratio of the metal occlusion portion decreases and reaches 50% at the center of the pixel array. In another implementation, the occlusion ratio trends of the metal occlusion structure in different rows of the same shared pixel structure differ in the column direction. Furthermore, the distribution of the metal occlusion structure varies in different corresponding rows in different types of shared pixel structures in the column direction. For example, the occlusion ratio of a single pixel is between 20% and 80%. The rule for the change in the occlusion ratio of left and right pixels can be that pixels on the left side of the pixel array with an occlusion ratio <50% gradually increase their occlusion ratio from the left to the right side, reaching exactly 50% on the left-right axis of symmetry of the pixel array; pixels on the left side of the pixel array with an occlusion ratio >50% gradually decrease their occlusion ratio from the left to the right side, reaching exactly 50% on the left-right axis of symmetry of the pixel array.

[0109] Please see Figure 5 and Figure 6 As shown, based on the design of this application, two comparative examples are provided.

[0110] Please see Figure 5 The diagram shows a cross-sectional view of a pixel array with a high metal grid (HMG) structure, including a semiconductor substrate layer 101, an anti-reflection layer 102, a metal grid 103, a silicon oxide layer 104, a color filter layer 105, a planarization layer 106, and a microlens 107. Some pixels in the pixel array are focusing pixels with a metal semi-mask type and have a metal masking structure 108. Figure 1The arrows in the diagram illustrate the optical path through which the metal shielding structure 108 causes crosstalk to surrounding pixels. This is because metal has high reflectivity, and the light incident on the metal shielding structure 108 is reflected to produce reflected light. After passing through the organic planarization layer and microlens, this reflected light can be reflected again and enter neighboring pixels, which can easily cause crosstalk and lead to abnormal pixel signals near the focused pixel.

[0111] Please see Figure 6 The diagram shows a cross-sectional view of a pixel array employing a low-metal grid (LMG) structure, whose structure is similar to... Figure 1 The structures shown are basically the same, the difference being that... Figure 1 In the structure shown, the metal shielding structure 108 and the metal grid 103 are encased in a relatively thick silicon oxide layer 104. The top surface of the silicon oxide layer is substantially the same as or slightly higher than the top surface of the color filter layer 105, and is not covered by the color filter layer. Figure 2 In the structure shown, the silicon oxide layer 104 that encloses the metal shielding structure 108 and the metal grid 103 is relatively thin, and there is also a relatively thin color filter layer above the structure. Figure 2 The arrows also illustrate the optical path through which the metal shielding structure 108 causes crosstalk to surrounding pixels, and the same problem of abnormal pixel signals near the focus pixel caused by the metal shielding structure 108 exists.

[0112] The image sensor of this invention is easy to manufacture. A method for manufacturing the image sensor is provided herein, comprising the following steps:

[0113] A semiconductor substrate is provided, the semiconductor substrate including the photosensitive element;

[0114] The metal shielding structure and the optical antireflection layer are fabricated on the semiconductor substrate;

[0115] The microlens is fabricated on the optical antireflection layer;

[0116] The steps for forming the metal shielding structure and the optical antireflection layer include:

[0117] A metal shielding material layer and an optical antireflection material layer are sequentially formed on the semiconductor substrate, and the optical antireflection material layer and the metal shielding material layer are sequentially etched to obtain the metal shielding structure and the optical antireflection layer.

[0118] As an example, the process of fabricating the metal shielding structure and the optical antireflection layer also includes the step of fabricating a metal grating structure, wherein:

[0119] After forming a metal shielding material layer and an optical antireflection material layer sequentially on the semiconductor substrate, the optical antireflection material layer and the metal shielding material layer are etched sequentially to obtain the metal shielding structure, the metal grid structure and the optical antireflection layer. The metal shielding structure and the metal grid structure are integrally formed based on the metal shielding material layer.

[0120] Specifically, for the design of the metal shielding structure 402 and the optical anti-reflection layer 403 in this application, the corresponding material layers can be formed layer by layer, and then the material layers can be etched. Thus, the corresponding metal shielding structure 402 and optical anti-reflection layer 403 can be obtained simultaneously based on the etching process. This simplifies the process, saves on photomasks, reduces costs, and improves the stability of the process. Furthermore, in a preferred design, the metal shielding structure 402, the optical anti-reflection layer 403, and the metal grid structure 600 can also be obtained simultaneously based on the same metal material layer. That is, the corresponding metal shielding structure 402, the optical anti-reflection layer 403, and the metal grid structure 600 can be obtained simultaneously based on the etching process. Furthermore, a covering dielectric layer 700 can be fabricated on the formed structure. The above process steps are compatible with existing metal grid structures.

[0121] This invention also provides an electronic device, including an image sensor as described in any of the above embodiments. The electronic device can be a security monitoring device, vehicle electronics, a mobile phone camera, a machine vision device, etc. The image sensor based on this invention can acquire high-quality image information and can be used in infrared utilization devices.

[0122] In summary, the image sensor of this invention includes a pixel array, comprising multiple pixel units arranged in an array. A portion of these pixel units are image pixels, and another portion are focusing pixels. Each focusing pixel includes a microlens, a metal shielding structure, an optical anti-reflection layer, and a photosensitive element. The metal shielding structure is located below the microlens, and its vertical projection onto the plane of the microlens shields half of the microlens. The optical anti-reflection layer covers the upper surface of the metal shielding structure, and the photosensitive element is located below the metal shielding structure. This invention can reduce reflection from the metal layer surface and decrease crosstalk near the focusing pixels without affecting the function of the focusing pixels, thereby improving the final image quality. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0123] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An image sensor comprising a pixel array, the pixel array comprising a plurality of pixel cells arranged in an array, a portion of the plurality of pixel cells being image pixels and another portion of the plurality of pixel cells being focus pixels, characterized in that, The focusing pixel comprises: a photosensitive element; a microlens located above the photosensitive element; a metal shielding structure located between the microlens and the photosensitive element to shield part of the incident light incident on the photosensitive element; an optical anti-reflection layer covering the upper surface of the metal shielding structure.

2. The image sensor of claim 1, wherein: The pixel array comprises a metal grid structure, and the metal shielding structure and the metal grid structure are located in the same layer.

3. The image sensor of claim 2, wherein: The optical anti-reflection layer also covers the upper surface of the metal grid structure; and / or the top surface of the metal shielding structure is flush with or lower than the top surface of the metal grid structure.

4. The image sensor of claim 2, wherein: Each pixel unit is provided with a color filter, and the color filter and the metal shielding structure are arranged in the following manner: The color filter and the metal shielding structure are located in the same layer, wherein there is a gap between the color filters of two adjacent pixel units; or the color filters of two adjacent pixel units are connected above the metal grid structure or above the metal shielding structure; or the color filter is located in a layer above the metal shielding structure.

5. The image sensor of claim 2, wherein: At least one of the metal shielding structure, the metal grid structure and the microlens is offset relative to the corresponding photosensitive element towards the center of the pixel array, and when the pixel unit is provided with a color filter, at least one of the metal shielding structure, the metal grid structure, the microlens and the color filter is offset relative to the corresponding photosensitive element towards the center of the pixel array.

6. The image sensor of claim 5, wherein: Each offset structure has a corresponding offset distance, and the offset distance of each type of offset structure increases in the direction from the center of the pixel array to the edge of the pixel array.

7. The image sensor of claim 1, wherein: The pixel array comprises at least two types of shared pixel structures for obtaining focusing information, each shared pixel structure comprises at least two focusing pixels, and there are at least two shared pixel structures with different shielding ratios of incident light in the same type of shared pixel structure.

8. The image sensor of claim 7, wherein: The shared pixel structure comprises four focusing pixels arranged in a 2x2 array, wherein the shared pixel structure comprises a staggered shielding pixel structure, the phases of the four metal shielding structures corresponding to the four focusing pixels in the staggered shielding pixel structure are the same, and the shielding ratios are different; and / or the shielding ratio of the metal shielding structure corresponding to a single focusing pixel in the shared pixel structure to incident light is between 20% and 80%.

9. The image sensor of claim 1, wherein: The optical anti-reflection layer comprises at least one of a metal layer and a dielectric layer.

10. The image sensor of claim 1, wherein: The optical anti-reflection layer comprises at least one interference extinction unit, and the reflection of light incident on the metal shielding structure is reduced based on the interference extinction unit.

11. The image sensor of claim 10, wherein: The interference extinction unit comprises a metal layer and a dielectric layer stacked; and / or an interference auxiliary layer is further provided between the interference extinction unit and the metal shielding structure.

12. The image sensor of claim 11, wherein: When the interference extinction unit comprises a metal layer and a dielectric layer stacked, the interference extinction unit is configured in the following manner: The metal layer surface is further provided with a surface transition layer, and / or the thickness of the metal layer is less than the thickness of the dielectric layer; and / or the thickness of the metal layer is between 5nm and 15nm. When the interference extinction unit and the metal shielding structure are further provided with an interference auxiliary layer, the interference auxiliary layer and the metal layer in the interference extinction unit are made of the same material, and / or the metal material of the interference auxiliary layer is different from that of the metal shielding structure.

13. The image sensor of claim 1, wherein: The optical anti-reflection layer covers the entire upper surface of the metal shielding structure or the upper surface of the part of the metal shielding structure close to the center area of the focus pixel is not covered by the optical anti-reflection layer; and / or the upper surface and the side surface of the combined structure composed of the metal shielding structure and the optical anti-reflection layer are covered by a medium layer; and / or the color filter corresponding to the focus pixel adopts a green color filter.

14. An electronic device, comprising: An image sensor as claimed in any one of claims 1 to 13.

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