Image sensor with optical structure for spot reduction

Abstract

An image sensor having an optical structure for spot reduction is described. The image sensor includes a plurality of pixels arranged to form an active pixel array, a plurality of contact pads disposed within a peripheral region of the image sensor surrounding the active pixel array, and an optical structure disposed within the peripheral region between the plurality of contact pads and the active pixel array. The optical structure is adapted to mitigate stray light from reaching the active pixel array.

Description

Technical Field

[0001] The present disclosure relates generally to image sensors and, in particular but not exclusively, to complementary metal oxide semiconductor image sensors. Background Art

[0002] Image sensors are a type of semiconductor device that have become ubiquitous and are now widely used in digital cameras, cell phones, security cameras, and medical, automotive, and other applications. As image sensors are integrated into a wider range of electronic devices, it is desirable to enhance the functionality, performance metrics, etc. of the electronic devices in as many ways as possible (e.g., resolution, power consumption, dynamic range, size, etc.) through both device architecture design and image acquisition processing.

[0003] A typical image sensor operates in response to image light reflected from an external scene being incident on the image sensor. The image sensor includes an array of pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charge when absorbing the image light. The image charge generated by the pixel light can be measured as an analog output image signal on a column bit line, which varies as a function of the incident image light. In other words, the amount of image charge generated is proportional to the intensity of the image light, which is read out from the column bit line as an analog image signal and converted into a digital value to produce a digital image (i.e., image data) representing the external scene.

[0004] However, the performance of an image sensor may be negatively affected by stray light that may inadvertently impinge on a pixel array having photosensitive elements. Stray light corresponds to unintended light that is incident on a pixel array, which may affect the amount of image charge generated and thus cause one or more imaging artifacts, such as light speckle. Light speckle is particularly due to internal reflections within an image sensor or lens grouping, which may degrade the quality of an image generated by the image sensor, or otherwise cause a given image to fail to accurately represent an external scene. Summary of the invention

[0005] In one aspect, the present disclosure relates to an image sensor comprising: a plurality of pixels arranged to form an active pixel array, wherein the plurality of pixels include a plurality of photodiodes formed within a semiconductor substrate and configured to generate image charges in response to incident light; a plurality of contact pads disposed in a peripheral region of the image sensor, the peripheral region surrounding the active pixel array; and an optical structure disposed on the semiconductor substrate in the peripheral region between the plurality of contact pads and the active pixel array, wherein the optical structure is suitable for mitigating stray light from reaching the active pixel array.

[0006] In another aspect, the present disclosure relates to an image sensor comprising: a plurality of pixels arranged to form an active pixel array, wherein the plurality of pixels include a plurality of photodiodes formed within a semiconductor substrate; an optical structure disposed within a peripheral region of the image sensor, the peripheral region surrounding the active pixel array; and a metal shield disposed within the peripheral region near a first side of the semiconductor substrate, wherein the metal shield is disposed between the first side of the semiconductor substrate and the optical structure, wherein the optical structure is segmented to form a plurality of regions of a first material separated by a low refractive index material, and wherein the plurality of regions of the first material have a first refractive index greater than a corresponding refractive index of the low refractive index material but less than a metal refractive index of a first metal contained in the metal shield. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of components must be labeled to avoid obscuring the drawings where appropriate. The drawings are not necessarily drawn to scale, emphasis instead being placed on illustrating the principles described.

[0008] Figure 1A A top view of an example of an image sensor having an optical structure suitable for mitigating stray light from reaching an active pixel array of the image sensor in accordance with an embodiment of the present disclosure is shown.

[0009] Figure 1B The optical structure according to the embodiment of the present disclosure is shown as follows: Figure 1A One possible implementation of the optical structure of image sensor 100 is shown in FIG.

[0010] Figure 1C The optical structure according to the embodiment of the present disclosure is shown as follows: Figure 1A One possible implementation of the optical structure of an image sensor is shown in FIG.

[0011] Figure 1D The optical structure according to the embodiment of the present disclosure is shown as follows: Figure 1A One possible implementation of the optical structure of an image sensor is shown in FIG.

[0012] Figure 2A The embodiment according to the present disclosure is shown along Figure 1B A cross-sectional view of line AA′ of the image sensor shown in FIG.

[0013] Figure 2B The embodiment according to the present disclosure is shown Figure 2A A more detailed view of the optical structure shown in .

[0014] Figure 2C The embodiment according to the present disclosure includes Figure 2A A top view of an example arrangement of multiple islands in the optical structure shown in FIG.

[0015] Figure 2D The embodiment according to the present disclosure includes Figure 2A 0046] A top view of another example arrangement of multiple islands forming an offset island pattern in the optical structure shown in FIG.

[0016] Figure 2E The embodiment according to the present disclosure includes Figure 2A A more detailed view of the attenuation structure in the multiple light attenuation structures.

[0017] Figure 2F A top view of an example two-by-two pixel cell array according to an embodiment of the present disclosure is shown, which may be included in Figure 1A in the active pixel array of an image sensor.

[0018] Figure 3 An example graph showing the relationship between reflection of light incident on an image sensor and angle when the image sensor includes an optical structure according to an embodiment of the present disclosure is shown.

[0019] Figure 4 An example stacked image sensor 400 is shown, which may be implemented in accordance with an embodiment of the present disclosure. Figures 1A to 1D The image sensor 100 shown in FIG. DETAILED DESCRIPTION

[0020] Embodiments of devices, systems, and / or methods related to image sensors with optical structures for speckle reduction are described herein. In the following description, many specific details are set forth to provide a thorough understanding of the embodiments. However, those skilled in the relevant art will recognize that the techniques described herein may be practiced without one or more of the specific details or using other methods, components, materials, etc. In other examples, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

[0021] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0022] Throughout this specification, several terms are used. These terms have their ordinary meaning in the fields from which they are derived, unless explicitly defined herein or the context of their use clearly indicates otherwise. It should be noted that component names and symbols can be used interchangeably throughout this document (e.g., Si and silicon); however, both have the same meaning.

[0023] Embodiments of image sensors having optical structures to mitigate stray light are described herein. In some embodiments, the image sensor will have an active pixel array (e.g., including multiple photodiodes to photogenerate image charge in response to incident light) surrounded by a peripheral region of the image sensor. It has been found that in an image sensor having a metal shield and a transparent cover extending within the peripheral region, stray light may be reflected within the peripheral region between the metal shield and the transparent cover and incident on the active pixel array, resulting in image quality degradation or other artifacts, such as light speckle. In order to mitigate the incidence of stray light on the active pixel array, the optical structure is configured to be disposed between the transparent cover and the metal shield within the peripheral region to reduce reflections. More specifically, the optical structure can be used as a light capture structure that captures or otherwise redirects stray light that will be disposed between the optical structure and the metal shield (e.g., to prevent a cascade effect in which stray light is reflected between the metal shield and the transparent cover until the stray light propagates toward or otherwise incident on the active pixel array). In some embodiments, the optical structure causes stray light to be reflected and scattered or captured between the optical structure and the metal shield until the stray light can be absorbed, attenuated, or otherwise directed away from the active pixel array. It has been found that in some embodiments, the optical structure can cause a reduction in reflection at the surface of the image sensor by as much as four to five times (e.g., in terms of the percentage of stray light reflected from the peripheral area).

[0024] Figure 1A A top view of an example of an image sensor 100 according to an embodiment of the present disclosure is shown, the image sensor 100 having an optical structure 110 suitable for mitigating stray light from reaching an active pixel array 105 of the image sensor 100. The image sensor 100 includes an active pixel area 102 and a peripheral area 104 that laterally surrounds the active pixel area 102 (e.g., when the image sensor 100 is viewed about an xy plane of a coordinate system 199). The active pixel area 102 of the image sensor 100 includes an active pixel array 105 formed in or on a semiconductor substrate 101. It should be appreciated that in some embodiments, the size of the active pixel area 102 is at least partially defined by the active pixel array 105, such that the active pixel area 102 includes the entire active pixel array 105. The peripheral area 104 of the image sensor 100 includes the optical structure 110 and a plurality of contact pads 115, each of which is formed in or on the semiconductor substrate 101. It should be appreciated that Figure 1AThe views presented in the drawings may omit certain features of image sensor 100 to avoid obscuring the details of the present disclosure. In other words, not all elements of image sensor 100 may be present in the drawings. Figure 1A Or labeled, shown, or otherwise illustrated in other figures throughout the present disclosure. It should be further understood that in some embodiments, image sensor 100 may not necessarily include all of the elements shown.

[0025] The active pixel array 105 of the image sensor 100 includes a plurality of pixels (see, for example, Figure 2A The plurality of pixels included in the active pixel array 105 may include, in particular, a plurality of photodiodes (see, for example, Figure 2A 1) to configure active pixel array 105 to generate image charge in response to incident light that will be read out and processed to form an image (e.g., to generate a digital image representing a scene external to image sensor 100). It should be appreciated that a plurality of photodiodes (e.g., pinned photodiodes) are formed or otherwise disposed within semiconductor substrate 101.

[0026] In the illustrated embodiment, semiconductor substrate 101 may correspond to a portion or all of a semiconductor wafer (e.g., a silicon wafer). In some embodiments, semiconductor substrate 101 includes or is otherwise formed of silicon, silicon-germanium alloy, germanium, silicon carbide alloy, indium gallium arsenide alloy, any other alloy formed from III-V compounds, combinations thereof, one or more epitaxial layers of the above materials, or a bulk substrate thereof. More specifically, semiconductor substrate 101 may correspond to any semiconductor material or combination of materials that may be doped or otherwise configured to include a plurality of photodiodes of active pixel array 105 of image sensor 100. For example, in some embodiments, semiconductor substrate 101 may correspond to one or more epitaxial layers (e.g., P or N doped silicon) formed on a carrier wafer. In such embodiments, a plurality of photodiodes of active pixel array 105 may be formed in one or more epitaxial layers corresponding to semiconductor substrate 101, while the carrier wafer may be removed or otherwise thinned during fabrication. In one embodiment, semiconductor substrate 101 is formed of intrinsic or extrinsic silicon having regions that are sufficiently doped to form a plurality of photodiodes of active pixel array 105.

[0027] The optical structure 110 is disposed within the peripheral region 104 of the image sensor 100 between the plurality of contact pads 115 and the active pixel array 105. In some embodiments, the optical structure 110 laterally surrounds the active pixel array 105 when the image sensor 100 is viewed from a top view. The optical structure is adapted or otherwise configured to mitigate stray light from reaching the active pixel array 105. The stray light corresponds to light that is incident on the image sensor 100 but not directly on the active pixel array 105 (e.g., light that is incident on the peripheral region 104 of the image sensor 100). As will be discussed in more detail later, the stray light may propagate from the peripheral region 104 toward the active pixel region 102 (e.g., via reflection or otherwise), which may result in various artifacts (e.g., light speckle) that may degrade the quality of an image generated by the image sensor 100. The optical structure 110 is configured to mitigate stray light from reaching the active pixel area 102 and the active pixel array 105 by redirecting the stray light away from the active pixel area 102 and the active pixel array 105 through scattering, refraction, reflection, absorption, or a combination thereof. In some embodiments, the configuration of the optical structure 110 is similar to that of a metal shield included in the image sensor 100 (e.g., see Figure 2A ) and a low refractive index material (e.g., see Figure 2A and Figure 2B The low refractive index material 217 shown in FIG. 1 ) in combination can be used together as a light capture structure that causes stray light to be reflected, scattered, or captured between the optical structure 110 and the metal shield until the stray light can be absorbed, attenuated, or otherwise directed away from the active pixel area 102.

[0028] It should be understood that the optical structure 110 includes one or more materials (e.g., a first material, a second material, etc.). The one or more materials may include titanium nitride, titanium, other metals, other metal nitrides, other metal oxides, or combinations thereof. In some embodiments, the one or more materials of the optical structure 110 form a homogeneous layer (e.g., a first layer of a first material, a second layer of a second material, etc., such as Figure 2A and Figure 2B ), which are stacked together to form a multilayer stack. In the same or other embodiments, optical structure 110 can be more generally described as being segmented to form multiple regions of a first material (or a combination of materials such as a second material or other or additional materials included in the multilayer stack) separated by a low refractive index material. In some embodiments, the multiple regions of the first material have a first refractive index that is greater than a corresponding refractive index of the low refractive index material but less than a metallic refractive index of a metal included in the metal shield (see, e.g., Figure 2B). In some embodiments, the optical structure 110 is disposed proximate to the metal shield (e.g., the metal shield 219 is disposed within the peripheral region 104 proximate to the first side 212 of the semiconductor substrate 101). More specifically, in some embodiments, the metal shield is disposed between the first side of the semiconductor substrate 101 and the optical structure 110 (e.g., the metal shield and the optical structure 110 both extend parallel to each other and to the xy plane of the coordinate system 199, as shown in FIG. Figure 2A ).

[0029] In the illustrated embodiment, one or more dimensions of the optical structure 110 are configured to be larger than corresponding dimensions of the active pixel array 105. For example, the optical structure 110 is defined by an inner boundary 111 and an outer boundary 112, both of which are disposed between the active pixel array 105 and the plurality of contact pads 115. Figure 1A As shown in , an inner width 173 as defined by the inner boundary 111 of the optical structure 110 (extending parallel to the y-direction of the coordinate system 199) and an outer width 174 as defined by the outer boundary 112 of the optical structure 110 (extending parallel to the y-direction of the coordinate system 199) are each greater than a width 171 (extending parallel to the y-direction of the coordinate system 199) of the active pixel array 105. Similarly, an inner length 175 as defined by the inner boundary 111 of the optical structure 110 (extending parallel to the x-direction of the coordinate system 199) and an outer length 176 as defined by the outer boundary 112 of the optical structure 110 (extending parallel to the x-direction of the coordinate system 199) are each greater than a length 172 (extending parallel to the x-direction of the coordinate system 199) of the active pixel array 105. In the same or other embodiments, optical structure 110 is a monolithic structure having a first dimension (e.g., inner width 173, outer width 174, inner length 175, or outer length 176) that is greater than a second dimension (e.g., width 171 or length 172) of active pixel array 105 (see, e.g., Figure 1C and Figure 1D ). It will be appreciated that in some embodiments, the first dimension and the second dimension extend along a common direction or are otherwise parallel to each other. It will be appreciated that the inner width 173 and the inner length 175 can be the same or different. Similarly, the outer width 174 and the outer length 176 can be the same or different.

[0030] In some embodiments, the distance between the active pixel array 105 and the plurality of contact pads 115 (e.g., the width of the optical structure 110) corresponds to an optical structure width 177. In some embodiments, the optical structure width 177 is at least 600 μm or greater to provide sufficient space for mitigating stray light within the peripheral region 104 of the image sensor 100. In some embodiments, the optical structure width 177 may be constant. In other embodiments, the optical structure width 177 varies (e.g., the minimum distance that the optical structure extends is different in the x-direction and the y-direction of the coordinate system 199). It should be appreciated that in some embodiments, Figure 1A Image sensor 100 shown in FIG. 1 may not necessarily be drawn to scale because one or more components may be disposed in or on semiconductor substrate 101 within peripheral region 104 but between optical structures 110 and active pixel array 105 (e.g., one or more photodiodes associated with an optical black pixel reference array and / or a dummy array, such as Figure 2A ).

[0031] In the illustrated embodiment, a plurality of contact pads 115 are disposed within the peripheral region 104 of the image sensor 100 and may provide external signal connections (e.g., between the image sensor 100 and a host or image processor). In some embodiments, the plurality of contact pads 115 laterally surround the optical structure 110. The plurality of contact pads 115 may include one or more conductive metals (e.g., metals such as Al, Au, Cu, other metals, metal alloys, polysilicon, other conductive materials, or combinations thereof) to facilitate electrical connection to one or more metal layers included in a metallization region of the image sensor 100 (e.g., a back end of a wire portion of the image sensor 100 to facilitate connections between components of the image sensor 100).

[0032] Figure 1B An optical structure 110-A according to an embodiment of the present disclosure is shown. Figure 1A One possible implementation of the optical structure 110 of the image sensor 100 is shown in FIG. Figure 1B The optical structure 110-A may include Figure 1A The optical structure 110 may have the same or similar features (e.g., overall size, relative position with respect to other components of the image sensor 100, composition, functionality, etc.) as the optical structure 110 of the image sensor 100.

[0033] In the illustrated embodiment, optical structure 110-A includes a plurality of islands 116 disposed within peripheral region 104 and collectively surrounding active pixel array 105. More specifically, plurality of islands 116 are arranged in rows and columns, and are further positioned to at least partially surround active pixel array 105 laterally (e.g., when image sensor 100 is viewed from an xy plane of coordinate system 199). It should be appreciated that the dimensions (e.g., length, width) of individual islands included in plurality of islands 116 are smaller than the dimensions (e.g., length, width) of active pixel array 105. Figure 1A ), and the common dimensions of the optical structures 110-A (e.g., Figure 1A The inner width 173, the outer width 174, the inner length 175 or the outer length 176 of the plurality of islands 116 are still larger than the size of the active pixel array 105. In some embodiments, individual islands included in the plurality of islands may be square or rectangular in shape (e.g., lateral dimensions of 0.15 μm×0.15 μm, 0.20 μm×0.20 μm, 0.25 μm×0.25 μm, 0.30 μm×0.30 μm, 0.5 μm×0.5 μm, or other dimensions). Therefore, in some embodiments, individual islands included in the plurality of islands 116 may have a width from 0.10 μm to 1.00 μm (e.g., measured along the direction of the y-axis of the coordinate system 199) and a length from 0.10 μm to 1.00 μm (e.g., measured along the direction of the x-axis of the coordinate system 199).

[0034] In some embodiments, adjacent islands included in the plurality of islands 116 are separated from each other by a low refractive index material (see, for example, a first island 116-1 adjacent to a second island 116-2 is separated from each other by a low refractive index material). Figure 2B 100). The low refractive index materials 217 shown in FIG. 10 are separated from each other. The separation distance between adjacent islands included in the plurality of islands 116 may be uniform or different. In some embodiments, the separation distance between adjacent islands is uniform and further optimized to mitigate stray light having a predetermined incident angle (e.g., an incident angle of 30° or greater) relative to the normal to the surface of the image sensor 100.

[0035] like Figure 1B, the individual islands included in the plurality of islands 116 each share a common shape (e.g., a rectangle or square as shown, or other shapes such as a circle, an oval, a triangle, a pentagon, a hexagon, an octagon, any other regular or irregular polygon, or other closed shape) and are evenly separated from adjacent islands. However, in other embodiments, the plurality of islands 116 may have different shapes (e.g., a rectangle or square as shown, or other shapes such as a circle, an oval, a triangle, a pentagon, a hexagon, an octagon, any other regular or irregular polygon, other closed shapes, or combinations thereof) and / or have uneven separation distances between adjacent islands included in the plurality of islands 116.

[0036] Figure 1C An optical structure 110-B according to an embodiment of the present disclosure is shown. Figure 1A One possible implementation of the optical structure 110 of the image sensor 100 is shown in FIG. Figure 1C The optical structure 110-B may include Figure 1A The optical structure 110 may have the same or similar features (e.g., overall size, relative position with respect to other components of the image sensor 100, composition, functionality, etc.) as the optical structure 110 of the image sensor 100.

[0037] In the illustrated embodiment, the optical structure 110-B is a monolithic structure that is patterned to form a plurality of openings 118. Each opening included in the plurality of openings 118 is filled with a low refractive index material (e.g., Figure 2B ) to form a plurality of islands that are laterally surrounded by one or more materials of the optical structure 110-B. More specifically, the optical structure is segmented to form regions of one or more materials (e.g., a first material, a second material, etc.) separated by individual islands of low refractive index material included in the plurality of islands. It should be understood that Figure 1C The optical structure 110-B can be considered as Figure 1B In particular, optical structure 110-B may have a pattern that is the opposite of the pattern of optical structure 110-A. Thus, the plurality of openings 118 of optical structure 110-B may have the same or similar features (e.g., in terms of shape, size, or arrangement) as the plurality of islands 116 of optical structure 110-A. In other words, both optical structure 110-A and optical structure 110-B are each segmented or otherwise patterned to form a plurality of islands 116 made of a low refractive index material (e.g., Figure 1B The optical structure 110-A and Figure 1C 110 -B) separated into a plurality of regions of the first material (e.g., included in Figure 1B The optical structure 110-A and Figure 1C110 -B) to configure optical structures 110 -A, 110 -B to mitigate stray light from reaching active pixel array 105. In some embodiments, the separation distance between segments can be optimized to mitigate stray light at specific incident angles on image sensor 100.

[0038] In some embodiments, Figure 1C The optical structure 110-B is a monolithic structure (e.g., formed from a single continuous shape or block) having a second dimension that is larger than the active pixel array 105 (e.g., as shown in FIG. Figure 1A The first dimension (e.g., width 171 or length 172) of the Figure 1A 173, outer width 174, inner length 175, or outer length 176). It should be appreciated that in some embodiments, the first dimension and the second dimension extend along a common direction or are otherwise parallel to each other. It should be further appreciated that in some embodiments, the first material having a first refractive index (e.g., included in Figure 1C ) is larger than the low refractive index material (e.g., contained in the black region of the optical structure 110-B shown in FIG. Figure 1C In addition, it should be appreciated that the individual openings in the plurality of openings 118 included in the optical structure 110-B may have a common shape (e.g., a rectangle or square as shown, or other shapes such as a circle, an ellipse, a triangle, a pentagon, a hexagon, an octagon, any other regular or irregular polygon, or similar shapes for Figure 1B 10-A) and are evenly separated from adjacent openings included in optical structure 110-B. However, in other embodiments, plurality of openings 118 may have different shapes (e.g., rectangular or square as shown, or other shapes such as circular, elliptical, triangular, pentagonal, hexagonal, octagonal, any other regular or irregular polygon, other closed shape, or combination thereof) and / or have uneven separation distances between adjacent openings included in plurality of openings 118.

[0039] It should be understood that Figure 1B The optical structure 110-A and Figure 1COne difference between the optical structure 110-B of the optical structure 110-A and the optical structure 110-B is that the optical structure 110-B is a monolithic structure, while the optical structure 110-A is formed of individually isolated islands contained in the plurality of islands 116, which may have different advantages or limitations in terms of manufacturability, depending on the geometric features (e.g., size) of the plurality of islands 116 of the optical structure 110-A and / or the plurality of openings 118 of the optical structure 110-B. For example, the plurality of islands 116 of the optical structure 110-A and / or the plurality of openings 118 of the optical structure 110-B may have different sizes, which means that the ease of manufacture and / or accurate reproduction of the optical structure 110-A and / or the optical structure 110-B may be different based on the critical dimensions of the dimensions relative to the manufacturing technology used to form the corresponding optical structure.

[0040] Figure 1D An optical structure 110-C according to an embodiment of the present disclosure is shown. Figure 1A One possible implementation of the optical structure 110 of the image sensor 100 is shown in FIG. Figure 1D The optical structure 110-C may include Figure 1A The optical structure 110-C may have the same or similar features (e.g., overall size, relative position relative to other components of the image sensor 100, composition, function, etc.) as the optical structure 110 of the image sensor 100. In the illustrated embodiment, the optical structure 110-C is a second dimension (e.g., such as Figure 1A The first dimension (e.g., width 171 or length 172) of Figure 1A 173, outer width 174, inner length 175, or outer length 176). It should be appreciated that in some embodiments, the first dimension and the second dimension extend along a common direction or are otherwise parallel to each other. As shown, the optical structure 110-C is a monolithic structure having a first dimension extending from an inner peripheral boundary to an outer peripheral boundary (e.g., from Figure 1A 110 -C may be a monolithic structure that is continuous and complete (e.g., has no openings or gaps) from the inner boundary 111 to the outer boundary 112 shown in FIG. 110 -C. In some embodiments, the optical structure 110 -C may be a sheet of one or more materials (e.g., a first layer of a first material, a second layer of a second material, etc.) having a flat upper surface and a central opening aligned with the active pixel array 105. In some embodiments, when the plurality of openings 118 are omitted, the optical structure 110 -C may correspond to Figure 1C The optical structure 110 -B is shown in FIG.

[0041] Figure 2A 1. FIG. 1 shows a circuit diagram of a circuit comprising an optical structure 110-A according to an embodiment of the present disclosure. Figure 1B 200 -AA' of the image sensor 100 shown in FIG. 1 . It should be understood that Figures 1B to 1D An image sensor 100 is shown having different embodiments of an optical structure 110 (eg, optical structures 110-A, 110-B, and 110-C). Figure 2A The elements of the image sensor 100 shown in FIG. 1 are not limited to having only the optical structure corresponding to the optical structure 110-A. Specifically, according to embodiments of the present disclosure, the image sensor 100 may alternatively or additionally utilize other embodiments of the optical structure (e.g., Figure 1C The optical structure 110-B, Figure 1D It should be further understood that Figure 2A The cross-sectional view 200-AA′ shown in FIG. 2 may be mirrored to extend across the entire image sensor 100 (eg, the peripheral region 104 of the image sensor extends around the active pixel region 102, as shown in FIG. 2 ). Figures 1A to 1D ).

[0042] Return to reference Figure 2A, the image sensor 100 includes a semiconductor substrate 101 having a first side 212 (e.g., a backside or front side) and a second side 211 (e.g., a frontside or back side), a plurality of contact pads 115 (e.g., a metal such as Al, Au, Cu, other metals, metal alloys, polysilicon, other conductive materials, or combinations thereof), an optical structure 110-A including a plurality of islands 116 (e.g., one or more materials that may include titanium nitride, titanium, other metals, other metal nitrides, other metal oxides, or combinations thereof), a plurality of deep trench isolation (DTI) structures 206 (e.g., one or more 207 (e.g., a high-k dielectric such as hafnium oxide, aluminum oxide, tantalum oxide, or any other material having a dielectric constant greater than silicon dioxide), a material stack 208 (e.g., one or more layers of high-k dielectric layers such as tantalum oxide, hafnium oxide, aluminum oxide, or any other material having a dielectric constant higher than silicon dioxide) for providing surface passivation and / or anti-reflection benefits, a buffer layer 209 (e.g., one or more dielectric or oxide materials such as silicon dioxide), a metal shield The plurality of photodiodes 220-1, 220-2, 220-3, and 220-4 may be made of a doped region having an opposite charge carrier type to the majority charge carrier type of the semiconductor substrate 101, such that the doped region has a lower refractive index than the plurality of islands 116 and / or the metal shield 219, and a plurality of photodiodes 220-1, 220-2, 220-3, and 220-4. The outer periphery of the impurity region forms a PN junction or a PIN junction of the photodiode), a metal grid 221 (for example, aluminum, copper, tungsten or other metal), a plurality of color filters 223 (one or more red, green, blue, infrared, colorless, transparent, cyan, magenta, yellow, black or any other color filter for filtering visible light or invisible light contained in the incident light 198), a plurality of micro lenses 224 (for example, a molded plastic or polymer material for forming an optical structure that focuses or otherwise directs the incident light onto the plurality of photodiodes 220), an active pixel array (for example, Figures 1A to 1D, a plurality of pixels 225 of an active pixel array 105 shown in the figure, a plurality of light attenuation structures 226 (e.g., one or more materials that may include titanium nitride, titanium, other metals, other metal nitrides, other metal oxides, or combinations thereof), a shallow trench isolation (STI) structure 242 (e.g., one or more dielectric or oxide materials, such as silicon dioxide), a first metal layer 244 (e.g., gold, silver, aluminum, copper, tantalum, other metal materials, or combinations thereof) included in a metallization region of the image sensor 100, and an interlayer dielectric 245 (e.g., silicon dioxide or other insulating material) included in a metallization region of the image sensor 100.

[0043] Disposed in the active pixel area 102 of the image sensor 100 are a plurality of pixels 225 that collectively form an active pixel array having a segmented pixel architecture (eg, Figures 1A to 1D 19. The active pixel array 105 shown in FIG. 19 is an image sensor 100 that includes an active pixel array 105 shown in FIG. 20. However, it should be appreciated that in other embodiments, the image sensor 100 may not have a split pixel architecture. In the illustrated embodiment, the plurality of pixels 225 include at least two types of pixels, including a first pixel 225-H and a second pixel 225-L. It should be appreciated that the first pixel 225-H and the second pixel 225-L do not necessarily differ in geometric size or area, but rather in sensitivity to incident light 198. In one embodiment, the second pixel 225-L is more sensitive to incident light 198 than the first pixel 225-H due to the plurality of attenuation structures 226 being optically disposed proximate to the first side 212 of the semiconductor substrate 101 between the first photodiodes (e.g., 220-2, 220-4) included in the plurality of photodiodes 220 and the corresponding optically aligned color filters (e.g., 223-2 and 223-4). Since the first pixel 225-H may not be as easily saturated by the incident light 198 as the second pixel 225-L, the split pixel architecture of the image sensor 100 facilitates high dynamic range image acquisition of the external scene. Specifically, the plurality of light attenuation structures 226 attenuate the intensity of light propagating through the first pixel 225-H via absorption, reflection, etc. It should be understood that in some embodiments, the individual light attenuation structures included in the plurality of light attenuation structures 226 each correspond to a multilayer stack structure including a first layer of a first material and a second layer of a second material (see, e.g., Figure 2E ).

[0044] like Figure 2AAs shown in , individual pixels included in the plurality of pixels 225 each include one of the plurality of photodiodes 220. Individual microlenses are optically aligned with underlying photodiodes included in the plurality of photodiodes and are shaped to focus or otherwise (e.g., in combination with one or more lenses included in a lens module of the image sensor) direct incident light 198 through underlying color filters included in the plurality of color filters to the underlying photodiodes to generate image charges representing an external scene of the image sensor 100. The plurality of color filters 223 may include green ("G"), red ("R"), blue ("B") color filters to form full-color image pixels. In other embodiments, additional or different color filters may be included in the plurality of color filters 223 (e.g., one or more red, green, blue, infrared, colorless, transparent, cyan, magenta, yellow, black, or any other color filters to filter visible or invisible light included in the incident light 198). In some embodiments, each of the plurality of photodiodes 220 is laterally surrounded by one of the plurality of DTI structures 206, which may correspond to an insulating material (e.g., silicon dioxide) filled in a trench lined with a liner material 207 (e.g., a high-k dielectric such as hafnium (IV) oxide, aluminum (III) oxide, tantalum (V) oxide, or any other material or combination of materials having a dielectric constant greater than silicon dioxide). In some embodiments, the liner material 207 may also be disposed between the buffer layer 209 and the semiconductor substrate 101 to provide surface passivation, or otherwise included in the material stack 208. The active pixel region 102 further includes a metal grid 221, which corresponds to one or more metal materials disposed between adjacent color filters (e.g., laterally surrounding individual color filters included in the plurality of color filters 223) to mitigate optical or electrical crosstalk between adjacent pixels included in the plurality of pixels 225. In some embodiments, a dielectric layer having a lower refractive index than each of the plurality of color filters 223 is disposed on the metal grid 221 to form a low refractive index grid. In such embodiments, the dielectric layer and the metal grid 221 together optically isolate and separate adjacent color filters included in the plurality of color filters 223. In some embodiments, the metal grid 221 is surrounded and embedded in the dielectric layer. In the example shown, the metal grid 221 is embedded in the low refractive index material 217, such as Figure 2A In some embodiments, the first metal included in the metal grid 221 may correspond to tungsten.

[0045] In the illustrated embodiment, a plurality of contact pads 115, an optical structure 110-A including a plurality of islands 116, a material stack 208, a low refractive index material 217, a buffer layer 209, a metal shield 219, a shallow trench isolation (STI) structure 242, a first metal layer 244 included in a metallization region of the image sensor 100, and an interlayer dielectric 245 included in a metallization region of the image sensor 100 are at least partially disposed within the peripheral region 104. In some embodiments, the metal shield 219 is disposed in or on the semiconductor substrate 101 and is proximate to the first side 212 of the semiconductor substrate 101 within the peripheral region 104. The metal shield is further disposed between the first side 212 of the semiconductor substrate 101 and the optical structure 110-A. In the same or other embodiments, individual islands in the plurality of islands 116 included in the optical structure 210-A each correspond to a multilayer stack structure including a first layer of a first material and a second layer of a second material (see, e.g., Figure 2B ). In addition, in some embodiments, individual islands in the plurality of islands 116 included in the optical structure 110 -A are each completely encapsulated by the low refractive index material 217 .

[0046] In some embodiments, the peripheral region 104 further includes at least one of an optical black reference array 260, a dummy array 262, or a peripheral circuit system 264 included in the image sensor 100, which may be formed in or on the semiconductor substrate 101 between the plurality of contact pads 115 and the active pixel array (e.g., the plurality of pixels 225). In most embodiments, a metal shield 219 is disposed between the optical structure 110-A and at least one of the optical black reference array 260, the dummy array 262, or the peripheral circuit system 264 included in the image sensor 100. In some embodiments, the metal shield 219 may mitigate or otherwise prevent incident light from reaching the optical black reference array 260 to ensure accurate black level detection. In the illustrated embodiment, the dummy array 262 is disposed between the optical black reference array 260 and the peripheral circuit system 264. However, other configurations (e.g., an optical black reference array disposed between the dummy array 262 and the peripheral circuit system 264) may be utilized in other embodiments. In some embodiments, the optical black reference array 260 and the dummy array 262 may each include a plurality of photodiodes (e.g., similar to or otherwise identical to the plurality of photodiodes 220) arranged in an array. The photodiodes included in the optical black reference array 260 may be isolated or otherwise shielded from light (e.g., by a metal shield 219) to configure the image charge generated by the photodiodes included in the optical black reference array 260 to correspond to a black reference level or dark current of the image sensor 100 (e.g., for dark current calibration or compensation when processing signals from or otherwise associated with the plurality of pixels 225 included in the active pixel array 105). In most embodiments, the photodiodes in the dummy array 262 may not be used for signal generation. Rather, the photodiodes in the dummy array 262 may be used to provide spacing, a buffer region, or otherwise mitigate noise or crosstalk between the peripheral circuitry 264 and the black reference array 260. In some embodiments, the peripheral circuitry 264 may include an array of decoupling capacitors to reduce circuitry noise between the semiconductor substrate 101 and the underlying logic die (see, e.g., Figure 4 ). In some embodiments, support circuitry that may be included in peripheral circuitry 264 may include, but is not limited to, row and column decoders and drivers, analog signal processing chains, digital imaging processing blocks, memories, timing and control circuits, input / output interfaces, vertical scanners, sample and hold circuitry, amplifiers, analog / digital converter circuitry, and any other embodiments of logic and / or circuitry suitable for the functionality of image sensor 100.

[0047] Peripheral region 104 further includes a plurality of contact pads 115 (e.g., metals such as Al, Au, Cu, other metals, metal alloys, polysilicon, other conductive materials, or combinations thereof) to facilitate electrical connection to one or more metal layers (e.g., first metal layer 244) included in a metallization region of image sensor 100 (e.g., a back end of a line portion of image sensor 100 that facilitates connection between components of image sensor 100). It should be appreciated that STI structures 242 (e.g., oxide materials such as silicon dioxide or other insulating materials) are disposed proximate second side 211 of semiconductor substrate 101 and further electrically isolate each individual contact pad included in the plurality of contact pads 115.

[0048] In the illustrated embodiment, both the active pixel region 102 and the peripheral region 104 include a material stack 208 (e.g., one or more material layers, which may include one or more high-k dielectric layers formed of tantalum oxide, hafnium oxide, aluminum oxide, or other oxide materials having a dielectric constant greater than that of silicon dioxide) to passivate surface hydroxyls on the first side 212 of the semiconductor substrate 101 and / or mitigate reflections at the interface defined by the first side 212 of the semiconductor substrate 101. In addition, both the active pixel region 102 and the peripheral region 104 include a buffer layer 209 (e.g., an oxide material such as silicon dioxide) to mitigate stress caused by processing (e.g., during chemical mechanical polishing). As shown, both the material stack 208 and the buffer layer 209 may extend continuously across the active pixel region 102 and the peripheral region 104. In some embodiments, the material stack 208 and the buffer layer 209 are disposed between the plurality of photodiodes 220 and the plurality of light attenuation structures 226. In the same or other embodiments, metal shield 219 is disposed between optical structure 110-A and both material stack 208 and buffer layer 209. In some embodiments, both material stack 208 and buffer layer 209 are disposed between optical structure 110-A and at least one of optical black reference array 260, dummy array 262, or peripheral circuitry 264 included in image sensor 100.

[0049] like Figure 2A, a transparent cover 240 (e.g., glass or other transparent material) also extends across both the active pixel area 102 and the peripheral area 104 to cover or otherwise protect the light receiving surface of the image sensor 100 while still allowing incident light 198 to reach the light receiving surface. As shown, a plurality of light attenuating structures 226 are disposed between the transparent cover 240 and the plurality of photodiodes 220. In addition, the optical structure 110-A is disposed between the transparent cover 240 and the metal shield 219. Similarly, the optical structure 110-A is disposed between the transparent cover 240 and at least one of the optical black reference array 260, the dummy array 262, or the peripheral circuitry 264 included in the image sensor 100.

[0050] exist Figure 2A In the illustrated embodiment of , incident light 198 includes stray light 198-A and 198-B, which is incident on the peripheral area 104 of the image sensor. However, since the incident angle is oblique (e.g., an incident angle of 30° relative to the normal of the surface of one or more components of the image sensor (e.g., the surface of the metal shield 219)), if it is optical structure 110-A (or other embodiments of optical structure 110, such as optical structure 110-B and / or 110-C), then the stray light 198-A (as shown) can be reflected from the metal shield 219, and then reflected from the inner surface of the transparent cover 240, and finally incident on the active pixel area 102. However, the optical structure 110-A, in combination with the low refractive index material 217 and the metal shield 219, forms a light trapping structure that redirects or otherwise traps light (e.g., by scattering, refraction, reflection, and / or absorption) to reduce reflections from between the metal shield 219 and the transparent cover 240, as shown by stray light 198-B. For example, stray light 198-B may be repeatedly reflected between one or more of the plurality of islands 116 and the metal shield 219, which may result in attenuation of the stray light 198-B or otherwise inhibit the stray light 198-B from reaching the active pixel region 102. In other words, various embodiments of the optical structure 110 (e.g., optical structures 110-A, 110-B, and / or 110-C) configure the image sensor 100 to mitigate instances of stray light 198-A, and more generally, mitigate stray light from reaching the active pixel region 102.

[0051] It should be further appreciated that certain elements of the image sensor 100 may have relative relationships. For example, in the illustrated embodiment, at least portions of individual light attenuation structures included in the plurality of light attenuation structures 226 of the optical structure 110-A and individual islands included in the plurality of islands 116 are aligned along a common plane 280 (e.g., a plane aligned parallel to the xy plane of the coordinate system 199). This is because, in some embodiments, the plurality of light attenuation structures 226 of the optical structure 110-A and the plurality of islands 116 (or more generally the optical structure 110-A) may share common components (e.g., the plurality of islands 116 or more generally the optical structure 110-A and the plurality of light attenuation structures 226 may be manufactured simultaneously to reduce costs or otherwise simplify the manufacture of the image sensor 100). Similarly, in some embodiments, the metal shield 219 and the metal grid 221 may be aligned along a common plane (e.g., parallel to the common plane 280) and further share common components (e.g., the metal shield 219 and the metal grid 221 may be manufactured simultaneously to reduce costs or otherwise simplify the manufacture of the image sensor 100).

[0052] Figure 2B The embodiment according to the present disclosure is shown Figure 2A . The illustrated view includes a plurality of islands 116 (e.g., a first island 116-1 and a second island 116-2) of the optical structure 110-A, wherein individual islands 116 included in the plurality of islands are completely encapsulated in a low refractive index material 217 and further disposed over a metal shield 219. More specifically, the low refractive index material 217 is disposed between the plurality of islands 116 (or more generally the optical structure 110-A) and the metal shield 219. Furthermore, adjacent islands included in the plurality of islands 116 (e.g., a first island 116-1 is adjacent to a second island 116-2, wherein no intervening islands are included in the plurality of islands 116 disposed between the first island 116-1 and the second island 116-2) are separated from one another by the low refractive index material 217.

[0053] In the illustrated embodiment, the plurality of islands 116 (or more generally the optical structure 210-A) comprises one or more materials (e.g., a first material 231 and a second material 232), which may be homogenous layers of one or more given materials. In other words, the optical structure 110-A is a multilayer stack structure comprising a first layer of the first material 231 and a second layer of the second material 232. In most embodiments, the layers included in the multilayer stack structure have substantially the same lateral dimensions (e.g., the width and length of the first layer and the second layer are substantially the same). It should be understood that the term "substantially" corresponds to a difference of 10% or less between the comparative features to account for process variations. In the same or other embodiments, the depths of the thickness layers included in the multilayer stack structure may be the same or different (e.g., the first layer and the second layer may have the same or different thicknesses). In some embodiments, the optical structure 110-A is not limited to two layers and / or two different materials. In other words, additional materials and / or additional layers may be included in the optical structure 110-A to facilitate mitigation of stray light. For example, in some embodiments, there may be more than one individual layer of each of the first material 231 and the second material 232 (e.g., layers of the first material 231 and the second material 232 may be repeated alternately to include more than two layers in the multilayer stack structure of the optical structure 110-A) to mitigate stray light having a specific incident angle. In the same or other embodiments, the layers of the optical structure 110-A are not limited to the first material 231 and the second material 232. Rather, additional materials or material layers may be further included in the optical structure 110-A.

[0054] In some embodiments, the optical structure 110 is configured to mitigate stray light by acting as a light capturing structure that redirects or otherwise captures light (e.g., by scattering, refraction, reflection, and / or absorption) to reduce reflections from the metal shield 219. In some embodiments, this is achieved at least in part by having the composition of one or more materials included in the optical structure 110 have a particular relative relationship in refractive index to nearby elements (e.g., the low refractive index material 217 and the metal shield 219).

[0055] In some embodiments, the first material 231 is titanium nitride, and the second material 232 is titanium. However, in other embodiments, the first material 231 and the second material 232 may be different materials as long as they meet certain design criteria of the optical structure 110-A to configure the optical structure 110-A to mitigate stray light. Specifically, in some embodiments, the first material 231 has a first refractive index, the second material 232 has a second refractive index, the first metal included in the metal shield has a metallic refractive index, and the low refractive index material has a corresponding refractive index. In such embodiments, the first refractive index of the first material 231 and the second refractive index of the second material 232 are each less than the metallic refractive index of the first metal included in the metal shield 219, but greater than the corresponding refractive index of the low refractive index material. In other words, the individual islands in the plurality of islands 116 included in the optical structure 110-A each include a first material having a first refractive index that is less than the metallic refractive index of the first metal included in the metal shield 219 but greater than the corresponding refractive index of the low refractive index material 217. It should be understood that in some embodiments, the compositional configuration of the optical structure 110-A (i.e., a multi-layer stacked structure) combined with the geometric dimensions and / or relative spacing of the plurality of islands 116 causes the optical structure 110-A to redirect stray light away from the active pixel area of ​​the image sensor (e.g., the stray light becomes trapped between the plurality of islands 116 and the metal shield 219, causing the stray light to be reflected, refracted, scattered, absorbed, attenuated, or a combination thereof).

[0056] In some embodiments, adjacent islands included in the plurality of islands 116 are separated from each other by a low refractive index material (see, for example, a first island 116-1 adjacent to a second island 116-2 separated from each other by a low refractive index material 217). The separation distances between adjacent islands included in the plurality of islands 116 may be uniform or different. In some embodiments, the separation distances between adjacent islands are uniform and further optimized to mitigate stray light having a predetermined incident angle (e.g., 30°) relative to the normal to the surface of the image sensor 100. More specifically, adjacent islands included in the plurality of islands 116 are separated from each other by a first separation distance 252 between the first island 116-1 and the second island 116-2. In the same or other embodiments, the adjacent islands are separated from the metal shield 219 by a second separation distance 266. In the same or other embodiments, the first separation distance 252 between the adjacent islands is greater than a combination of the thickness 263 of the adjacent islands and the second separation distance (e.g., the separation distance between the plurality of islands 116 and the metal shield 219, which corresponds to the second separation distance 266). In other words, the first separation distance 252 is greater than the sum of the thickness 263 and the second separation distance 266. In some embodiments, the plurality of islands 116 of the optical structure 110-A may be optimized to mitigate stray light having a predetermined incident angle based on the following equation:

[0057]

[0058] Wherein, d corresponds to a separation distance 252 between adjacent islands contained in the plurality of islands 116, t corresponds to a total thickness represented by a thickness 263 of the plurality of islands 116 plus a second separation distance 266, and θ corresponds to a predetermined incident angle of light relative to a normal (e.g., the xy plane of the coordinate system 199) to a surface of the image sensor (e.g., the illuminated surface plane of the first side 212).

[0059] In some embodiments, the plurality of islands 116 may be defined as having a length 261 (eg, along the x-axis of the coordinate system 199) and a width (eg, along the y-axis of the coordinate system 199 (eg, Figure 1B ), or otherwise corresponds to Figure 2C 199 ). In some embodiments, the length 261 and / or width of individual islands included in the plurality of islands 116 may be from 0.10 μm to 1.00 μm. In some embodiments, the first thickness 267 of the first material 231 and / or the second thickness 268 of the second material (e.g., along the z-axis of the coordinate system 199) is from 1 nm to 100 nm. In one embodiment, the first thickness 267 of the first material (e.g., titanium nitride) is greater than the second thickness 268 of the second material (e.g., titanium). In the same or other embodiments, the first thickness 267 of the first material is from 5 nm to 70 nm, while the second thickness 268 is from 2 nm to 60 nm. It should be understood that in some embodiments, the first thickness 267 and the second thickness 268 may be the same or different.

[0060] Figure 2C The embodiment according to the present disclosure includes Figure 2A FIG. 1 is a top view of an example arrangement of multiple islands 116 in the optical structure 110-A shown in FIG. 1 . It should be understood that Figure 2C The example arrangement of multiple islands shown in Figure 1C The optical structure 110-B shown in FIG. 1 is implemented in (eg, forming Figure 1C The plurality of openings 118 of the plurality of islands shown in FIG. 1 may have the same or similar arrangement as the plurality of islands 116. Return to Reference Figure 2C, individual islands included in the plurality of islands 116 of the optical structure, each defined as having a length 261 (e.g., a length along the x-axis of the coordinate system 199) and a width 291 (e.g., a width along the y-axis of the coordinate system 199), each have a common shape (e.g., a rectangle or square as shown, or other shapes such as a circle, an ellipse, a triangle, a pentagon, a hexagon, an octagon, any other regular or irregular polygon, or other closed shape) and are evenly separated from neighboring islands. However, in other embodiments, the plurality of islands 116 may have geometric sizes and / or different shapes (e.g., a rectangle or square as shown, or other shapes such as a circle, an ellipse, a triangle, a pentagon, a hexagon, an octagon, any other regular or irregular polygon, other closed shapes, or combinations thereof). In addition, in the illustrated embodiment, the individual islands included in the plurality of islands 116 are arranged into rows (e.g., R1, R2, R3, R4, etc.) and columns (e.g., C1, C2, C3, C4, etc.) such that the peripheral boundaries of the plurality of islands in common rows and / or common columns are aligned.

[0061] Figure 2D The embodiment according to the present disclosure includes Figure 2A 1 is a top view of another example arrangement of multiple islands 116 in an optical structure 110-A shown in FIG. 1 to form an offset island pattern (e.g., the low refractive index material 217 forms an offset grid defined by the positions of the multiple islands 116). It should be understood that Figure 2D The example arrangement of multiple islands shown in Figure 1C The optical structure 110-B shown in FIG. 1 is implemented in (eg, forming Figure 1C The plurality of openings 118 of the plurality of islands shown in FIG. 1 may have the same or similar arrangement as the plurality of islands 116. Return to Reference Figure 2C , adjacent rows included in a row (e.g., R1, R2, R3, R4) or adjacent columns included in a column (not labeled) are not aligned to configure the plurality of islands 116 to form an offset island pattern. For example, a first group of islands included in the plurality of islands 116 and positioned within R1 are not aligned with a second group of islands included in the plurality of islands 116 positioned within R2. In other words, an offset island pattern can be defined as having islands positioned in alternating rows that are aligned but offset from islands included in adjacent rows (e.g., individual islands in the plurality of islands 116 included in R1 and R3 are aligned relative to each other along direction 271, but are not aligned with adjacent islands in the plurality of islands 116 included in R2 and R4 along direction 272).

[0062] Figure 2E The embodiment according to the present disclosure includes Figure 2ADetailed view of an attenuation structure in the plurality of light attenuation structures 226. In some embodiments, each individual attenuation structure included in the plurality of light attenuation structures 226 may be disposed between a corresponding color filter and a corresponding photodiode of a given one of the first pixels 225-H included in the active pixel array (e.g., as shown in FIG. 1 ). Figure 2A As shown, each of the plurality of light attenuation structures 226 may include one or more materials (eg, a third material 281 and a fourth material 282, which may be respectively Figure 2B 1 and 1 ). The first material 231 and the second material 232 of the plurality of islands 116 shown in are the same). One or more materials of the plurality of light attenuation structures 226 may be a homogeneous layer of one or more given materials. In other words, the individual attenuation structures included in the plurality of light attenuation structures 226 may be a multilayer stack structure including corresponding layers of the third material 281 and the fourth material 282. In some embodiments, the plurality of light attenuation structures 226 are not limited to two layers and / or two different materials. In other words, additional materials and / or additional layers may be included in the plurality of light attenuation structures 226 to attenuate incident light. For example, in some embodiments, there may be more than one individual layer of each of the third material 281 and the fourth material 282 (for example, the layers of the third material 281 and the fourth material 282 may be repeated alternately to include more than two layers in the multilayer stack structure of the plurality of light attenuation structures 226). In the same or other embodiments, the layers of the plurality of light attenuation structures 226 are not limited to the third material 281 and the fourth material 282. Specifically, additional materials or material layers may be further included in the plurality of light attenuation structures 226. In some embodiments, the third material 281 is titanium nitride and the fourth material 282 is titanium. However, in other embodiments, the third material and the fourth material may be different materials. In some embodiments, the plurality of light attenuation structures 226 and the optical structures (e.g., Figure 1A The optical structure 110 shown in Figure 1B , 2A and the optical structure 110-A shown in 2B, Figure 1C The optical structure 110-B shown in Figure 1D The optical structures 110 -C) shown in FIG. 1 may be formed simultaneously (eg, to reduce processing costs and / or manufacturing complexity of the image sensor) and have the same composition.

[0063] In some embodiments, end portions 292 of the plurality of light attenuating structures 226 may be coplanar with the optical structure 110 (e.g., one or more elements of the optical structures 110-A, 110-B, or 110-C may be coplanar with the end portions 292 of the plurality of light attenuating structures 226). It should be appreciated that the end portions 292 correspond to the ends or distal ends of the plurality of light attenuating structures 226 that are substantially planar. It should be further appreciated that in some embodiments, one or more materials of the plurality of light attenuating structures 226 and individual layers of the optical structure 110 may be coplanar. For example, when referring to Figure 2B and 2D 110-A, and the layer of the fourth material 282 included in the end portions 292 of the plurality of light attenuating structures 226 may be coplanar with the layer of the second material 232 included in the plurality of islands 116 of the optical structure 110-A. In the same or different embodiments, the first thickness of the first material 231 may be substantially the same as the third thickness of the layer of the third material 281 included in the end portions 292 of the plurality of light attenuating structures 226. The second thickness of the second material 232 may be substantially the same as the fourth thickness of the layer of the fourth material 282 included in the end portions 292 of the plurality of light attenuating structures 226.

[0064] Figure 2F A top view of an example two-by-two pixel cell array 250 is shown, which may be included in the Figure 1A In the illustrated embodiment, the two-by-two pixel unit array 250 corresponds to an image sensor (eg, Figures 1A to 1D , which includes four pixel cells (e.g., 222-R, 222-G1, 222-G2, 222-B) arranged in a two-by-two pattern. In the illustrated embodiment, the minimal repeating unit includes two green pixel cells (e.g., 222-G1 and 222-G2), one red pixel cell (e.g., 222-R), and one blue pixel cell (e.g., 222-B) to form a full-color image pixel cell. It should be understood that the "color" of a given pixel cell indicates the color filter (e.g., 222-R) included in each pixel associated with the given pixel cell. Figure 2A However, as previously discussed, different arrangements may be utilized (e.g., other than a minimal repeating unit including two green, one blue, and one red pixel cells), and may include, but are not limited to, one or more red, green, blue, infrared, colorless, transparent, cyan, magenta, yellow, black, or any other pixel cells with corresponding color filters to filter visible or invisible light.

[0065] We should further understand that Figure 2F Multiple examples of the minimal repeating unit shown in can collectively form an active pixel array (e.g., Figures 1A to 1D The active pixel array 105 shown in FIG. 1 is a pixel array 105 shown in FIG. 1 . Figure 2F According to an embodiment of the present disclosure, each pixel unit includes a two-by-two arrangement of four pixels (e.g., three "low-light" pixels represented by the suffix "L" and one "high-contrast" pixel represented by the suffix "H") included in a plurality of pixels 225 arranged in a two-by-two array, each having a Figure 2A The corresponding structure indicated in .

[0066] Figure 3 An example graph 300 showing reflection relative to the angle of light incident on an image sensor when the image sensor includes an optical structure is shown in accordance with an embodiment of the present disclosure. More specifically, the graph shows the reflection of an embodiment without an optical structure (e.g., Figure 1A ), corresponding to line 391 and having Figure 1D The embodiment of the image sensor of the optical structure 110-C shown in FIG. 3 and the corresponding line 392 having Figure 1B 1 and 1 . An optical simulation of an embodiment of an image sensor of optical structure 110-A shown in FIG. 1 with respect to reflection of incident light. As can be seen, optical structure 110-C provides marginal improvement in reducing reflection of stray light when comparing line 391 to line 390. In addition, when comparing line 392 to both lines 391 and 390, optical structure 110-A provides significant improvement in mitigating stray light.

[0067] Figure 4 An example stacked image sensor 400 is shown, which may be implemented in accordance with an embodiment of the present disclosure. Figures 1A to 1D According to an embodiment of the present disclosure, a stacked image sensor 400 includes a semiconductor substrate 401 (which may correspond to Figures 1A to 1D The image sensor 100 shown in FIG. 1 and the second semiconductor substrate 451, each of which may correspond to a portion or the entirety of a semiconductor chip. The semiconductor substrate 401 includes an active pixel array 405, which may correspond to Figures 1A to 1D The active pixel array 105 shown in FIG. 4A and includes optical structures to mitigate stray light. The second semiconductor substrate 451 includes pixel cell circuitry 455 (eg, for reading out image charge from the active pixel array 405 ).

[0068] exist Figure 4In the illustrated embodiment, the stacked image sensor 400 is a stacked complementary metal oxide semiconductor (CMOS) device, which is at least partially formed by a semiconductor substrate 401 (e.g., a first die) and a second semiconductor substrate 451 (e.g., a second die), which are stacked and coupled together (e.g., electrically and / or physically) in a stacked chip scheme implemented via bonding (e.g., oxide bonding, metal bonding, hybrid bonding), silicon connection (e.g., through silicon vias), other suitable circuit coupling technology, or a combination thereof. In addition, it should be understood that Figure 4 The views presented in the drawings may omit certain elements of the stacked image sensor 400 to avoid obscuring the details of the present disclosure. In other words, not all elements of the stacked image sensor 400 may be present in the drawings. Figure 4 The present disclosure may be labeled, shown, or otherwise illustrated in other drawings or figures within or throughout the present disclosure.

[0069] Figure 4 The stacked chip scheme of the stacked image sensor 400 shown in FIG. 4 distributes components across multiple substrates. Specifically, the semiconductor substrate 401 includes photosensitive elements (e.g., multiple photodiodes, such as pinned photodiodes, etc., to form a plurality of active pixel arrays 405) including a plurality of photosensitive elements (e.g., multiple photodiodes, such as pinned photodiodes, etc., to form a plurality of active pixel arrays 405). Figure 2A ), while the second semiconductor substrate 451 includes a pixel unit circuit system 455 associated with the active pixel array 405 (e.g., pixel transistors such as reset transistors, source follower transistors, row selection transistors, switchable conversion gain transistors, etc., analog / digital circuit systems, signal processing circuit systems, or other circuit systems, or any one or a combination thereof, so as to facilitate imaging of external scenes using pixels included in the active pixel array 405). In other words, the second semiconductor substrate 451 unloads at least a portion of the circuit system associated with the active pixel array 405 from the semiconductor substrate 401, which advantageously provides additional space on the semiconductor substrate 401 (e.g., reducing the pixel pitch, increasing the photodiode sensing area relative to the total pixel area, etc.).

[0070] In some embodiments, the active pixel array 405 may be coupled to the pixel cell circuitry 455 by one or more hybrid bonds, by through silicon vias, other suitable circuitry coupling techniques, or combinations thereof. In some embodiments, the space saved on the semiconductor substrate 401 by offloading the circuitry to the second semiconductor substrate 451 (or other subsequent substrate in a stacked chip scheme) may be repurposed to increase the size of the individual photodiodes included in each individual pixel included in the active pixel array 405 to allow for increased pixel size, density, sensitivity, full well capacity, combinations thereof, etc. Additionally or alternatively, the functionality of the stacked image sensor 400 may be facilitated because the second semiconductor substrate 451 may have space for additional components or circuitry that may otherwise not be suitable on a separate substrate containing both the active pixel array 405 and the pixel cell circuitry 455, without affecting the performance and / or functionality of the stacked image sensor 400.

[0071] In the illustrated embodiment, a second semiconductor substrate 451 is coupled to the semiconductor substrate 401 to form a stacked semiconductor device. The semiconductor substrate 401 includes an active pixel array 405 arranged in rows (e.g., R1, R2, R3, ... RY) and columns (e.g., C1, C2, C3, ... CX) to form an array of pixel cells and may include, among other things, optical structures (e.g., Figures 1A to 2B ) to mitigate the peripheral area 404 of stray light.

[0072] At least Figures 1A to 2F and Figure 4 The embodiments of the present disclosure shown in the drawings may utilize conventional semiconductor device processing and microfabrication techniques known to those of ordinary skill in the art, which may include but are not limited to photolithography, ion implantation, chemical vapor deposition, physical vapor deposition, thermal evaporation, sputtering deposition, reactive ion etching, plasma etching, wafer bonding, chemical mechanical planarization, etc. It should be understood that the techniques described are merely illustrative and not exhaustive, and that other techniques may be utilized to fabricate one or more components of the various embodiments of the present disclosure.

[0073] The above description of the illustrated examples of the present invention (including the contents described in the Abstract) is not intended to be exhaustive or to limit the present invention to the precise forms disclosed. As will be appreciated by those skilled in the relevant art, although specific examples of the present invention are described herein for illustrative purposes, various modifications are possible within the scope of the present invention.

[0074] In light of the above detailed description, these modifications may be made to the present invention. The terms used in the appended claims should not be interpreted as limiting the present invention to the specific examples disclosed in the specification. Rather, the scope of the present invention will be determined entirely by the appended claims, which will be interpreted in accordance with established principles of claim interpretation.

Claims

1. An image sensor, comprising: a plurality of pixels arranged to form an active pixel array, wherein the plurality of pixels include a plurality of photodiodes formed within a semiconductor substrate and configured to generate image charge in response to incident light; a plurality of contact pads disposed within a peripheral region of the image sensor, the peripheral region surrounding the active pixel array; and An optical structure is disposed on the semiconductor substrate in the peripheral region between the plurality of contact pads and the active pixel array, wherein the optical structure is adapted to mitigate stray light from reaching the active pixel array.

2. The image sensor of claim 1 , further comprising a metal shield disposed in the peripheral region proximate to a first side of the semiconductor substrate, wherein the metal shield is disposed between the first side of the semiconductor substrate and the optical structure. 3 . The image sensor of claim 2 , wherein the metal shield comprises a first metal having a metal index of refraction, wherein the optical structure comprises a first material having a first refractive index less than the metal index of refraction of the first metal.

4. The image sensor of claim 3, further comprising a low refractive index material disposed between the optical structure and the metal shield, wherein the first refractive index of the first material is greater than a corresponding refractive index of the low refractive index material.

5. An image sensor according to claim 4, wherein the optical structure is a multilayer stack structure including a first layer of the first material and a second layer of a second material, the second material having a second refractive index less than the metal refractive index of the first metal but greater than the corresponding refractive index of the low refractive index material.

6. The image sensor of claim 2, wherein the optical structure comprises a plurality of islands, and wherein a low refractive index material is disposed between the plurality of islands and the metal shield. 7 . The image sensor according to claim 6 , wherein adjacent islands included in the plurality of islands are separated from each other by the low refractive index material.

8. An image sensor according to claim 6, wherein the metal shield comprises a first metal having a metallic refractive index, and wherein individual islands contained in the plurality of islands in the optical structure each comprise a first material having a first refractive index less than the metallic refractive index of the first metal but greater than the corresponding refractive index of the low refractive index material.

9. The image sensor of claim 7, wherein the adjacent islands are separated from each other by a first separation distance, wherein the adjacent islands are separated from the metal shield by a second separation distance, and wherein the first separation distance is greater than a combination of a thickness of the adjacent islands and the second separation distance.

10. The image sensor of claim 6, wherein individual islands included in the plurality of islands are arranged in rows and columns and are further positioned to at least partially laterally surround the active pixel array. 11 . The image sensor of claim 10 , wherein adjacent rows included in the rows or adjacent columns included in the columns are not aligned to configure the plurality of islands to form an offset island pattern.

12. The image sensor according to claim 6 further comprises a plurality of light attenuation structures, wherein the plurality of light attenuation structures are disposed near the first side of the semiconductor substrate, wherein the plurality of light attenuation structures are further disposed between the plurality of photodiodes and the plurality of color filters included in the plurality of pixels of the active pixel array, and wherein individual islands included in the plurality of islands of the optical structure and individual attenuation structures included in the plurality of light attenuation structures each correspond to a multilayer stacked structure including a first layer of a first material and a second layer of a second material.

13. An image sensor according to claim 12, wherein (i) the first layer of the first material contained in the individual island is at least partially coplanar with the first layer of the first material contained in the individual attenuation structure, or (ii) the second layer of the second material contained in the individual island is at least partially coplanar with the second layer of the second material contained in the individual attenuation structure.

14. The image sensor according to claim 6 further comprises a plurality of light attenuation structures, wherein the plurality of light attenuation structures are disposed proximate to the first side of the semiconductor substrate, wherein the plurality of light attenuation structures are further disposed between the plurality of photodiodes and a plurality of color filters included in the plurality of pixels of the active pixel array, wherein individual attenuation structures included in the plurality of light attenuation structures are at least partially aligned along a common plane with individual islands included in the plurality of islands of the optical structure.

15. An image sensor according to claim 14, wherein the plurality of pixels include a first pixel and a second pixel different from the first pixel, so that the active pixel array has a split pixel architecture, wherein the plurality of light attenuation structures are optically aligned to be disposed between a first photodiode associated with the first pixel included in the plurality of photodiodes and a corresponding optically aligned color filter included in the plurality of color filters, so that the second pixel is more sensitive to incident light than the first pixel.

16. The image sensor of claim 6 , further comprising a transparent cover extending over the active pixel array and the optical structure, wherein the optical structure is disposed between the transparent cover and the metal shield, and individual islands among the plurality of islands included in the optical structure are each completely encapsulated by the low refractive index material.

17. An image sensor according to claim 6, wherein the optical structure is a monolithic structure patterned to form a plurality of openings, each opening included in the plurality of openings is filled with the low refractive index material to form the plurality of islands, so that the optical structure is segmented to form a plurality of regions of a first material separated by individual islands of the low refractive index material included in the plurality of islands, and wherein the plurality of regions of the first material have a first refractive index greater than a corresponding refractive index of the low refractive index material but less than a metal refractive index of a first metal included in the metal shield.

18. The image sensor of claim 2, wherein the optical structure is a monolithic structure having a first dimension greater than a second dimension of the active pixel array, wherein the first dimension and the second dimension extend along a common direction.

19. The image sensor according to claim 2 further includes at least one of a peripheral circuit system, a dummy pixel array, or a black reference pixel array, wherein the peripheral circuit system, the dummy pixel array, or the black reference pixel array is disposed in the peripheral area of ​​the image sensor between the plurality of contact pads and the active pixel array, wherein the metal shield is disposed between the optical structure and at least one of the peripheral circuit system, the dummy pixel array, or the black reference pixel array.

20. An image sensor, comprising: a plurality of pixels arranged to form an active pixel array, wherein the plurality of pixels include a plurality of photodiodes formed within a semiconductor substrate; an optical structure disposed within a peripheral region of the image sensor, the peripheral region surrounding the active pixel array; and a metal shield disposed in the peripheral region proximate to a first side of the semiconductor substrate, wherein the metal shield is disposed between the first side of the semiconductor substrate and the optical structure, wherein the optical structure is segmented to form a plurality of regions of a first material separated by a low refractive index material, and wherein the plurality of regions of the first material have a first refractive index greater than a corresponding refractive index of the low refractive index material but less than a metal refractive index of a first metal contained in the metal shield.

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