Semiconductor Image Sensor

Abstract

Embodiments of the present invention relate to semiconductor image sensors. A backside illuminated BSI image sensor includes: a substrate including a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate; and a color filter disposed above the pixel sensor. The pixel sensor includes a plurality of first microstructures disposed above the back side of the substrate, and the color filter includes a plurality of second microstructures disposed above the back side of the substrate.

Description

Technical Field

[0001] The embodiments of the present invention relate to semiconductor image sensors. Background Technology

[0002] Digital cameras and other imaging devices use image sensors. An image sensor converts an optical image into digital data that can be represented as a digital image. An image sensor comprises an array of pixel sensors and supporting logic circuitry. The pixel sensors in the array are unit devices for measuring incident light, and the supporting logic circuitry facilitates the readout of the measurement results. One type of image sensor commonly used in optical imaging devices is the back-side illumination (BSI) image sensor. BSI image sensors can be manufactured and integrated into conventional semiconductor processes to achieve low cost, small size, and high integration. Furthermore, BSI image sensors feature low operating voltage, low power consumption, high quantum efficiency, low readout noise, and allow random access. Summary of the Invention

[0003] Embodiments of the present invention relate to a back-side illumination (BSI) image sensor, comprising: a substrate including a front side and a back side opposite to the front side; a plurality of pixel sensors disposed in the substrate, each of the pixel sensors including a photosensing device and a plurality of microstructures disposed on the back side of the substrate above the photosensing device; an isolation structure disposed in the substrate; a plurality of color filters disposed on the back side of the substrate above the pixel sensors; and a plurality of microlenses disposed above the color filters, wherein the microstructures and photosensing device of one of the pixel sensors are isolated from the microstructures and photosensing devices of adjacent pixel sensors by the isolation structure.

[0004] Embodiments of the present invention relate to a back-side illumination (BSI) image sensor, comprising: a substrate including a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate, the pixel sensor including a plurality of first microstructures disposed above the back side of the substrate; and a color filter disposed above the pixel sensor, the color filter including a plurality of second microstructures disposed above the back side of the substrate.

[0005] Embodiments of the present invention relate to a back-side illumination (BSI) image sensor, comprising: a substrate including a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate, the pixel sensor including a plurality of first microstructures disposed above the back side of the substrate and a plurality of second microstructures disposed above the front side of the substrate; and a color filter disposed above the pixel sensor, the color filter including a plurality of third microstructures disposed above the back side of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] When read in conjunction with the accompanying drawings, aspects of this disclosure are best understood from the following detailed description. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of explanation.

[0007] Figure 1A A cross-sectional view of a BSI image sensor according to an aspect of this disclosure in one or more embodiments.

[0008] Figure 1B for Figure 1A A partially magnified view of the BSI image sensor.

[0009] Figure 2A A cross-sectional view of a BSI image sensor according to an aspect of this disclosure in one or more embodiments.

[0010] Figure 2B for Figure 2A A partially magnified view of the BSI image sensor.

[0011] Figures 3 to 7 This is a partial enlarged view of a BSI image sensor according to aspects of this disclosure in some embodiments.

[0012] Figure 8 A cross-sectional view of a BSI image sensor according to an aspect of this disclosure in one or more embodiments.

[0013] Figures 9 to 12 This is a partial enlarged view of a BSI image sensor according to aspects of this disclosure in some embodiments. Detailed Implementation

[0014] The following disclosure provides numerous different embodiments or instances for implementing various features of the provided subject matter. Specific examples of elements and arrangements are described below to simplify this disclosure. Of course, these elements and arrangements are merely examples and are not intended to be limiting. For example, in the following description, the formation of a first feature over or on a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features may be formed between the first and second features such that the first and second features may not be in direct contact. Additionally, reference numerals and / or letters may be repeated in various instances of this disclosure. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0015] Additionally, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” “on,” and similar terms may be used herein to describe the relationship of one element or feature to another element(s) or feature(s), as illustrated in the figures. Besides the orientations depicted in the figures, the spatial relative terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein shall be interpreted accordingly.

[0016] As used herein, terms such as “first,” “second,” and “third” describe various elements, components, areas, layers, and / or segments, and these elements, components, areas, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, area, layer, or segment from another. Unless the context clearly indicates otherwise, the use of terms such as “first,” “second,” and “third” herein does not imply any order or sequence.

[0017] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and account for small variations. When used in conjunction with an event or situation, the terms may refer to a situation where the event or situation has clearly occurred or is very close to occurring. For example, when used in conjunction with a numerical value, the terms may refer to a range of variation less than or equal to ±10% of that value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two values ​​is less than or equal to ±10% of the average of the values, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%, then the two values ​​can be considered "substantially" the same or equal. For example, "substantially" parallel can refer to an angular variation range of less than or equal to ±10° relative to 0°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1°, less than or equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to ±0.05°. For example, "generally" vertical can refer to an angle variation range of less than or equal to ±10° relative to 90°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1°, less than or equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to ±0.05°.

[0018] As used herein, “microstructure” refers to a recessed or protruding structure on a non-uniform or rough surface that forms a substrate or color filter. As used herein, “groove” is a structure recessed from the periphery or edge of another structure, and “protrusion” is a structure that protrudes from the periphery or edge of another structure.

[0019] BSI image sensors comprise an array of pixel sensors. Typically, a BSI image sensor includes: an integrated circuit having a semiconductor substrate and photodiodes corresponding to the pixel sensors disposed within the substrate; a back-end processing (BEOL) metallization of the integrated circuit disposed above the front side of the substrate; and an optical stack including color filters and microlenses corresponding to the pixel sensors disposed above the back side of the substrate. As the size of BSI image sensors decreases, they face several challenges. One challenge is crosstalk between adjacent pixel sensors, and another is light collection. As BSI image sensors become smaller, the surface area for light collection becomes smaller, thereby reducing the sensitivity of the pixel sensors. This is problematic in low-light environments. Therefore, it is necessary to increase the absorption efficiency and angular response of the pixel sensors to improve the sensitivity of the BSI image sensors.

[0020] Therefore, this disclosure provides a BSI image sensor that includes a color filter with microstructures, thereby eliminating the need for microlenses and reducing the height of the optical stack. More importantly, the reduced height improves angular response. This disclosure further provides a BSI image sensor that includes a thin photodiode having microstructures positioned above the back and / or front sides, and due to the microstructures positioned above the back side, a longer light travel distance is generated within the photodiode. In other words, light is trapped within the thinner photodiode, thus improving the sensitivity of the pixel sensor.

[0021] Figure 1A This is a cross-sectional view of a BSI image sensor 100 according to aspects of this disclosure in some embodiments, and Figure 1B for Figure 1A A partially magnified view of the pixel sensor 110 of the BSI image sensor 100. (See image below.) Figure 1A and 1BAs shown, the BSI image sensor 100 includes a substrate 102, which includes, but is not limited to, a bulk semiconductor substrate such as, but not limited to, a bulk silicon (Si) substrate, or a silicon-on-insulator (SOI) substrate. The substrate 102 has a front side 102F and a back side 102B opposite to the front side 102F. The BSI image sensor 100 includes a plurality of pixel sensors 110 typically arranged in an array, each of which includes a light-sensing device, such as a photodiode 112 disposed in the substrate 102. In other words, the BSI image sensor 100 includes a plurality of photodiodes 112 corresponding to the pixel sensors 110. The photodiodes 112 are arranged in rows and columns in the substrate 102 and configured to accumulate charge (e.g., electrons) from photons incident thereon. Additionally, logic devices (not shown), such as transistors, are disposed on the front side 102F above the substrate 102 and configured to read out the photodiodes 112.

[0022] Back-to-office (BEOL) metallization stack 120 is disposed on the front side 102F of substrate 102. BEOL metallization stack 120 includes a plurality of metallization layers 122 stacked in interlayer dielectric (ILD) layers 124. One or more contacts of BEOL metallization stack 120 are electrically connected to logic devices. In some embodiments, ILD layers 124 may comprise a low-k dielectric material (i.e., a dielectric material with a dielectric constant less than 3.9) or an oxide, but this disclosure is not limited thereto. The plurality of metallization layers 122 may comprise metals such as copper (Cu), tungsten (W), or aluminum (Al), but this disclosure is not limited thereto. In some embodiments, another substrate (not shown) may be disposed between metallization structure 120 and an external connector such as a ball grid array (BGA) (not shown). And BSI image sensor 100 is electrically connected to other devices or circuits via external connectors, but this disclosure is not limited thereto.

[0023] Deep trench isolation (DTI) structure 104 is placed in substrate 102, such as Figure 1A and 1B As shown in the figure. In some embodiments, the DTI structure 104 can be formed by the following operations. For example, a first etching is performed from the back side 102B of the substrate 102. The first etching creates a plurality of deep trenches (not shown) surrounding the photodiode 112 and therebetween. An insulating material, such as silicon oxide (SiO), is then formed to fill the deep trenches using any suitable deposition technique, such as chemical vapor deposition (CVD). In some embodiments, at least the sidewalls of the deep trenches are lined with a coating 104c (in Figure 1B(Note: The text appears to be incomplete and contains errors. A more accurate translation would require the full context.) The coating 104c may comprise a metal, such as W, Cu, or AlCu, or a low-n material having a refractive index (n) less than that of the color filter formed below. The low-n material may comprise SiO or hafnium oxide (HfO), but this disclosure is not limited thereto. In some embodiments, the insulating material filling the deep trench may comprise a low-n insulating material. Planarization is then performed to remove excess insulating material, thus exposing the surface of the substrate 102 on the back side 102B, and obtaining the DTI structure 104 surrounding the photodiode 112 and therebetween, as shown below. Figure 1A and 1B As shown in the diagram. The DTI structure 104 provides optical isolation between adjacent pixel sensors 110 and photodiodes 112, thereby acting as a substrate isolation grid and reducing crosstalk.

[0024] In some embodiments, a plurality of color filters 150 corresponding to the pixel sensor 110 are placed on the back side 102B of the substrate 102 above the pixel sensor 110. Additionally, in some embodiments, a low-n structure 140 is disposed between the color filters 150. In some embodiments, the low-n structure 140 includes a grid structure and the color filters 150 are located within the grid. Therefore, the low-n structure 140 surrounds each color filter 150 and separates the color filters 150 from each other, as... Figure 1A and 1B As shown in the diagram. The low-n structure 140 may be a composite structure comprising multiple layers with a refractive index less than that of the color filter 150. In some embodiments, the low-n structure 140 may comprise a composite stack comprising at least a metal layer and a dielectric layer disposed above the metal layer. In some embodiments, the metal layer may comprise W, Cu, or AlCu. The dielectric layer comprises a material with a refractive index less than that of the color filter 150 or a material with a refractive index less than that of Si, but this disclosure is not limited thereto. Due to its low refractive index, the low-n structure 140 acts as a light guide to direct or reflect light to the color filter 150. Therefore, the low-n structure 140 effectively increases the amount of light incident on the color filter 150. Additionally, due to its low refractive index, the low-n structure 140 provides optical isolation between adjacent color filters 150.

[0025] Each of the color filters 150 is positioned above each of the corresponding photodiodes 112. The color filters 150 are assigned to light of a corresponding color or wavelength and are configured to filter out all light except for the assigned color or wavelength. Typically, the color filters 150 are assigned alternately between red, green, and blue light, such that the color filters 150 include red, green, and blue filters. In some embodiments, the red, green, and blue filters are arranged in a Bayer mosaic pattern, but this disclosure is not limited thereto.

[0026] In some embodiments, a plurality of microlenses 160 corresponding to the pixel sensor 110 are positioned above the color filter 150. It should be readily understood that the position and area of ​​each microlens 160 correspond to the position and area of ​​the color filter 150, such as... Figure 1A and 1B As shown in the image.

[0027] In some embodiments, each of the pixel sensors 110 includes a plurality of microstructures 130 disposed above the back side 102B of the substrate 102, such as Figure 1A and 1B As shown in the diagram. Additionally, multiple microstructures 130 are positioned above the photodiode 112 and surrounded by a DTI structure 104. The microstructures 130 and photodiode 112 of one pixel sensor 110 are isolated from the microstructures 130 and photodiode 112 of adjacent pixel sensors 110 by the DTI structure 104, as shown in the diagram. Figure 1A As shown in the figure. In some embodiments, the microstructure 130 can be formed by the following operations. A mask layer (not shown) is placed on the back side 102B above the surface of the substrate 102, and then a patterned photoresist (not shown) is formed over the mask layer. The substrate 102 is then etched from the back side 102B through the patterned photoresist and the mask layer, and thus a plurality of microstructures 130 are formed over the back side 102B of the substrate 102 in each of the pixel sensors 110. The patterned photoresist and the mask layer are then removed. In some embodiments, other operations such as wet etching may be performed. As a result, the upper and lower portions of the microstructure 130 are gradually narrowed or rounded to obtain a corrugated pattern, such as Figure 1A and 1B As shown in the figure. In some embodiments, the sidewalls of the microstructure 130 include at least an angle θ1 with the horizontal direction of the substrate (shown in the figure). Figure 1B The included angle θ1 is related to the material of the microstructure 130. In some embodiments, the included angle θ1 is related to the refractive index of the microstructure 130. For example, when the refractive index of the microstructure 130 is about 3.6, the included angle θ1 is between about 48° and about 58°. Light will be tilted to about 40° after passing through the microstructure 130. In addition, the light angle increases with the refractive index gap between the microstructure 130 and the dielectric layer 108. In some embodiments, the height of the microstructure 130 is between about 0.2 micrometers (μm) and about 0.7 μm, and the width of the microstructure 130 is between about 0.3 μm and about 0.6 μm, but this disclosure is not limited thereto. In addition, various microstructures 130 can be obtained by modifying the operations used to form the microstructure 130, such as Figures 3 to 5 As shown in the figure. Additionally, in some embodiments, the microstructures 130 are spaced apart from each other (e.g., Figure 6 (As shown in the figure). Those various microstructures 130 will be further described in one or more of the following embodiments.

[0028] In some embodiments, an anti-reflective coating (ARC) 106 and a dielectric layer 108 are placed on the back side 102B of the substrate 102 above the microstructure 130. For example... Figure 1B As shown, the surface of microstructure 130 is lined with a conformally formed ARC106. A dielectric layer 108 fills the spaces between microstructures 130 and provides a generally uniform surface over the back side 102B of substrate 102. In some embodiments, the dielectric layer 108 may comprise, for example, an oxide of silicon dioxide, but this disclosure is not limited thereto. Additionally, in some embodiments, another coating 109 corresponding to pixel sensor 110 may be placed over the front side 102F of substrate 102 for light reflection.

[0029] See Figure 1B Incident light is condensed by microlenses 160 above each color filter 150 and then focused onto the color filter 150. However, the incident light passing through the color filter 150 is scattered or diffused by the microstructure 130 of the pixel sensor 110. Furthermore, when entering the photodiode 112, the directly incident light is tilted or angled by the microstructure 130, thus creating a longer light travel distance in the photodiode 112. Additionally, light can be reflected back to the photodiode 112 by the coating 109 and the DTI structure 104. In other words, light is trapped in the photodiode 112, thus improving the sensitivity of the pixel sensor 110. Furthermore, due to the extended light travel distance, the thickness of the photodiode 112 or the substrate 102 can be reduced, thereby further simplifying and improving the manufacturing process.

[0030] Figure 2A This is a cross-sectional view of a BSI image sensor 200 according to aspects of this disclosure in some embodiments, and Figure 2B for Figure 2A A partially enlarged view of the pixel sensor 210 of the BSI image sensor 200. It should be noted that the same elements in the BSI image sensor 100 and BSI image sensor 200 may contain the same materials and / or be formed by the same operations, and therefore those details are omitted for brevity. The BSI image sensor 200 includes a substrate 202, and the substrate 202 has a front side 202F and a back side 202B opposite to the front side 202F. The BSI image sensor 200 includes a plurality of pixel sensors 210 typically arranged in an array. A plurality of light-sensing devices, such as photodiodes 212, corresponding to the pixel sensors 210, are placed in the substrate 202. The photodiodes 212 are arranged in rows and columns in the substrate 202. Additionally, logic devices (not shown), such as transistors, are placed above the front side 202F of the substrate 202 and configured to read out the photodiodes 212.

[0031] A BEOL metallization stack 220 is disposed on the front side 202F of the substrate 202. As mentioned above, the BEOL metallization stack 220 includes a plurality of metallization layers 222 stacked in the ILD layer 224. One or more contacts of the BEOL metallization stack 220 are electrically connected to logic devices. In some embodiments, another substrate (not shown) may be disposed between the metallization structure 220 and an external connector, such as a ball grid array (BGA) (not shown). The BSI image sensor 200 is electrically connected to other devices or circuits via the external connector, but this disclosure is not limited thereto. A DTI structure 204 is disposed in the substrate 202, as... Figure 2A and 2B As shown in the diagram. In some embodiments, the DTI structure 204 may comprise a low-n material with a refractive index less than that of the color filter formed below. In some embodiments, the DTI structure 204 may comprise an insulating material, wherein a low-n coating is sandwiched between the insulating material and the substrate 202. The DTI structure 204 surrounding the photodiode 212 and therebetween provides optical isolation between adjacent pixel sensors 210 and photodiode 212, thereby acting as a substrate isolation grid and reducing crosstalk.

[0032] In some embodiments, a plurality of color filters 250 corresponding to the pixel sensor 210 are placed on the back side 202B of the substrate 202 above the pixel sensor 210. Additionally, in some embodiments, a low-n structure 240 is disposed between the color filters 250. As mentioned above, the low-n structure 240 includes a grid structure and the color filters 250 are located within the grid. Therefore, the low-n structure 240 surrounds the color filters 250 and separates the color filters 250 from each other, as... Figure 2A and 2B As shown in the diagram, the low-n structure 240 can be a composite structure comprising multiple layers with a refractive index lower than that of the color filter 250. Due to its low refractive index, the low-n structure 240 acts as a light guide to direct or reflect light to the color filter 250. Therefore, the low-n structure 240 effectively increases the amount of light incident on the color filter 250. Additionally, due to its low refractive index, the low-n structure 240 provides optical isolation between adjacent color filters 250.

[0033] In some embodiments, each of the pixel sensors 210 includes a plurality of microstructures 230 disposed above the back side 202B. The microstructures 230 can be formed by the operations mentioned above, and therefore those details are omitted for brevity. As mentioned above, various types of microstructures 230 can be obtained by modifying the operations used to form the microstructures 230. These various microstructures 230 will be further described in one or more embodiments below. In some embodiments, an ARC 206 and / or a dielectric layer 208 are disposed above the microstructures 230 at the back side 202B of the substrate 202. Figure 2A and 2B As shown, the surface of microstructure 230 is lined with conformally formed ARC 206. Dielectric layer 208 fills the spaces between microstructures 230 and provides a generally uniform surface over the back side 202B of substrate 202. Additionally, in some embodiments, another coating 209 corresponding to pixel sensor 210 may be placed over the front side 202F of substrate 202 for light reflection, such as... Figure 2B As shown in the image.

[0034] In some embodiments, each of the color filters 250 comprises a plurality of microstructures 232 formed on the back side 202B of the substrate 202 above the pixel sensor 210. The color filters 250 are assigned to light of a corresponding color or wavelength and configured to filter out all light except the assigned color or wavelength. In some embodiments, the operations for forming the color filters 250 and the microstructures 232 may include forming a color filter layer and a patterned color filter layer for each of the different colors in the color assignment to obtain the color filter 250. After forming the color filter 250, a patterned photoresist (not shown) may be formed over the color filter 250. A process such as hot reflow may be performed to round or gradually narrow the patterned photoresist. Subsequently, the color filter 250 is etched via the rounded or gradually narrowed patterned photoresist to form a plurality of microstructures 232 in each of the color filters 250. In some embodiments, the operation for forming the microstructure 232 may include forming a photosensitive material layer (not shown) and a patterned photosensitive material layer over the color filter 250. In some embodiments, the photosensitive material layer and the color filter 250 may contain the same material. However, in other embodiments, the photosensitive material layer and the color filter 250 may contain different materials. Processes such as heat reflow may be performed to make the patterned photosensitive material layer rounded or gradually narrowed, such as... Figure 2A and 2B As shown in the figure. Therefore, multiple microstructures 232 are obtained. In addition, various microstructures 232 can be formed by modifying those operations used to form the microstructures 232, and various microstructures 232 of each of the color filters 250 will be further described according to one or more embodiments.

[0035] Figures 3 to 7 This is a partially enlarged view of a BSI image sensor 200 according to one or more embodiments. As mentioned above, each of the pixel sensors 210 of the BSI image sensor 200 includes a plurality of microstructures 230 formed above the back side 202B of the substrate 202, and each of the color filters 250 includes a plurality of microstructures 232 formed above the back side 202B of the substrate 202. In some embodiments, the microstructures 230 include a corrugated pattern in the cross-sectional view, such as... Figures 2A to 5As shown in the figure. In some embodiments, the sidewalls of the microstructure 230 include at least an angle θ1 with the horizontal direction of the substrate. As mentioned above, the angle θ1 is related to the refractive index of the microstructure 230. For example, when the refractive index of the microstructure 230 is about 3.6, the angle θ1 is between about 48° and about 58°, as shown in the figure. Figures 2A to 5 As shown in the illustration, but not limited thereto. In some embodiments, the microstructure 230 may include at least one central portion 230a and a plurality of peripheral portions 230b, wherein the bottom width of the central portion 230a is greater than the bottom width of the peripheral portions 230b, and the height of the microstructure 230 is the same. Figure 3 As shown in the diagram. Additionally, the sidewall of the central portion 230a forms an angle θ1 with the horizontal direction of the substrate, and the sidewall of the peripheral portion 230b forms another angle θ1' with the horizontal direction of the substrate, and angle θ1 is different from angle θ1', as shown in the diagram. Figure 3 As shown in the figure. In some embodiments, the microstructure 230 may include at least one central portion 230a and a plurality of peripheral portions 230b, wherein the height of the central portion 230a is greater than the height of the peripheral portions 230b, and the bottom width of the microstructure 230 is the same, as shown in the figure. Figure 4 As shown in the diagram. Additionally, the sidewall of the central portion 230a forms an angle θ1 with the horizontal direction of the substrate, and the sidewall of the peripheral portion 230b forms another angle θ1' with the horizontal direction of the substrate, and angle θ1 is different from angle θ1', as shown in the diagram. Figure 4 As shown in the illustration. In some embodiments, the microstructures 230 are spaced apart from each other, as illustrated in the illustration. Figure 5 As shown in the diagram. In other words, microstructure 230 is a discrete structure. Additionally, flat surfaces can be placed between adjacent microstructures 230, such as... Figure 5 The present disclosure is as shown, but is not limited thereto. Additionally, in some embodiments of this disclosure, the top surface of the DTI structure 204 is located between the bottom surface of the microstructure 230 and the bottom surface of the color filter 250, such as... Figures 2A to 5 As shown in the image.

[0036] Return to view Figures 2A to 5 As mentioned above, each of the color filters 250 includes a plurality of microstructures 232 formed above the back side 202B of the substrate 202. In some embodiments, the microstructure 232 may include at least one central portion 232a and a plurality of peripheral portions 232b. The central portion 232a includes an isosceles triangular profile, while the peripheral portions 232b include non-isosceles triangular profiles, such as right-angled triangular profiles, as shown below. Figure 2BThe following is shown, but this disclosure is not limited thereto. The bottom width of the central portion 232a is greater than the bottom width of the peripheral portion 232b. Additionally, at least one sidewall of the central portion 232a includes an angle θ2 with respect to the material of the color filter 250 in the horizontal direction of the substrate. In some embodiments, the angle θ2 is related to the refractive index of the color filter 250. For example, when the refractive index of the color filter 250 is about 1.6, the angle θ2 is between about 35° and about 55°. Figure 2B As shown, but not limited thereto. Light will be tilted to approximately 20° after passing through microstructure 232. Furthermore, the light angle increases with the refractive index of color filter 250. In some embodiments, the sidewalls of the peripheral portion 232b include another angle θ2' with the horizontal direction of the substrate, and this angle θ2' differs from the angle θ2, such as... Figure 2B As shown in the figure, but not limited thereto. In some embodiments, all microstructures 232 include the same bottom width and isosceles triangular profile, and the sidewalls of microstructures 232 include an angle θ2 with the horizontal direction of the substrate, such as... Figure 3 and 4 As shown in the figure. In some embodiments, the top surface of the low-n structure 240 is located between the topmost portion of the microstructure 232 and the bottom surface of the color filter, as illustrated in the figure. Figure 3 As shown in the figure. In some embodiments, the topmost portion of the microstructure 232 in each of the color filters 250 is coplanar with the top surface of the low-n structure 240, and the lowest portion of the microstructure 232 is located between the top surface of the low-n structure 240 and the bottom surface of the color filter, as shown in the figure. Figure 4 and 5 As shown in the figure. In some embodiments, the sidewalls of the microstructure 232 have two different included angles θ2 and θ2' with the substrate in the horizontal direction, and at least the included angle θ2 is between about 35° and about 55°, as illustrated in the figure. Figure 5 This disclosure is shown in the document, but is not limited thereto.

[0037] In some embodiments, the microstructure 230 may be arranged symmetrically with respect to axis A, such as... Figures 3 to 5 As shown in the figure, but not limited thereto. In some embodiments, the microstructure 232 may be arranged symmetrically with respect to axis A', such as Figures 3 to 5 The present disclosure is as shown, but is not limited thereto. It should be understood that the arrangement of microstructures 230 and 232 is independent.

[0038] As mentioned above, various types of microstructures 230 and 232 can be obtained by modifying the operations used to form microstructures 230 and 232. For example, in some embodiments, rounding or narrowing operations are not performed. Therefore, the microstructures 232 are spaced apart from each other, such as... Figure 6As shown in the figure. In other words, the microstructure 230 is a discrete structure. In some embodiments, the width "b" of the microstructure 230 is between about 0.3 μm and about 0.6 μm, the spacing width "e" between the microstructures 230 is between about 0.3 μm and about 0.6 μm, and the height "h1" of the microstructure 230 is between about 0.2 μm and about 0.7 μm, but this disclosure is not limited thereto. See still Figure 6 In some embodiments, the operations used to form the microstructures 232 are modified. For example, omitting the heat reflow operation causes the microstructures 232 to be spaced apart from each other, such as... Figure 6 As shown in the figure. In other words, microstructure 232 is a discrete structure. In some embodiments, the width "a" of microstructure 232 is between about 0.3 μm and about 0.6 μm, the spacing width "d" between microstructures 232 is between about 0.3 μm and about 0.6 μm, and the height "h2" of microstructure 232 is between about 0.2 μm and about 0.6 μm, but this disclosure is not limited thereto. In some embodiments, the height h2 of microstructure 232 is smaller than the height h1 of microstructure 230, but this disclosure is not limited thereto.

[0039] Please refer to Figure 7 It should be noted that the various microstructures 230 and 232 are formed independently. Therefore, the various microstructures 230 and 232 can have any combination. For example, in some embodiments, the pixel sensor 210 may include continuous or joined microstructures 230, and the color filter 250 may include continuous or joined microstructures 232, such as... Figures 2A to 5 As shown in the figure. In some embodiments, the pixel sensor 210 may include discrete microstructures 230, and the color filter 250 may include discrete microstructures 232, such as Figure 6 As shown in the figure. In some embodiments, the pixel sensor 210 may include continuous or joined microstructures 230, while the color filter 250 may include discrete microstructures 232, such as Figure 7 As shown in the text, or vice versa.

[0040] Return to view Figure 2B Due to the microstructure 232 of the color filter 250, the light entering the color filter 250 is diffused, thus achieving a longer light travel distance. More importantly, microlenses are no longer needed in the BSI image sensor 200 because the color filter 250 containing the microstructure 232 acts as a color lens. Therefore, the height of the optical stack is reduced and the angular response is improved. See still Figure 2BDue to the microstructures 232 of the color filter 250 and the pixel sensor 210, light is diffused within the color filter 250 and the photodiode 212. Furthermore, when entering the photodiode 212, directly incident light passes through the microstructures 230 and 232 at an angle or tilt, thus achieving a longer light travel distance. This increases the absorption rate of the photodiode 212. Additionally, since light can be reflected back to the photodiode 212 through the DTI structure 204 and the coating 209, it is considered that the light is trapped within the photodiode 212. Figure 2B As shown in the diagram, more photons are absorbed, thus improving the sensitivity of the BSI image sensor 200. Furthermore, due to the extended light travel distance, the thickness of the photodiode 212 or the substrate 202 is reduced, thereby further simplifying and improving the fabrication process.

[0041] See Figure 8 This document provides cross-sectional views of a BSI image sensor 300 according to aspects of this disclosure in some embodiments. It should be noted that the same elements in BSI image sensors 100 / 200 and BSI image sensor 300 may comprise the same materials and / or be formed by the same operations, and therefore those details are omitted for brevity. The BSI image sensor 300 includes a substrate 302 having a front side 302F and a back side 302B opposite to the front side 302F. The BSI image sensor 300 includes a plurality of pixel sensors 310 typically arranged in an array. A plurality of photodiodes 312 corresponding to the pixel sensors 310 are disposed in the substrate 302. Additionally, logic devices (not shown), such as transistors, are disposed above the front side 302F of the substrate 302 and configured to enable readout of the photodiodes 312.

[0042] A BEOL metallization stack 320 is disposed on the front side 302F of the substrate 302. As mentioned above, the BEOL metallization stack 320 includes a plurality of metallization layers 322 stacked in the ILD layer 324. One or more contacts of the BEOL metallization stack 320 are electrically connected to logic devices. In some embodiments, another substrate (not shown) may be disposed between the metallization structure 320 and an external connector, such as a ball grid array (BGA) (not shown). The BSI image sensor 300 is electrically connected to other devices or circuits via an external connector, but this disclosure is not limited thereto. A DTI structure 304 is disposed in the substrate 302, as... Figure 8As shown in the diagram. In some embodiments, the DTI structure 304 may comprise a low-n material with a refractive index less than that of the color filter formed below. In some embodiments, the DTI structure 304 may comprise an insulating material, wherein a low-n coating is sandwiched between the insulating material and the substrate 302. The DTI structure 304 surrounding the photodiode 312 and therebetween provides optical isolation between adjacent pixel sensors 310 and photodiode 312, thereby acting as a substrate isolation grid and reducing crosstalk.

[0043] In some embodiments, each of the pixel sensors 310 includes a plurality of microstructures 330 formed above the back side 302B of the substrate 302 and a plurality of microstructures 334 formed above the front side 302F, such as Figure 8 As shown in the figure. In some embodiments, ARC 306 and dielectric layer 308 are disposed on the back side 302B of substrate 302 above microstructure 330. As mentioned above, the surface of microstructure 330 may be lined with conformally formed ARC 306. Dielectric layer 308 fills the spaces between microstructures 330 and provides a generally uniform surface over the back side 302B of substrate 302. In some embodiments, dielectric layer 307 and ARC 309 are disposed on the front side 302F of substrate 302 above microstructure 334, as shown in the figure. Figure 8 As shown in the figure. Dielectric layer 307 fills the space between microstructures 334 and provides a generally uniform surface above the front side 302F of substrate 302. ARC 309 is formed above the uniform surface to improve light reflection. The microstructures 330 and 334 of each in pixel sensor 310 will be further described according to one or more embodiments.

[0044] In some embodiments, a plurality of color filters 350 corresponding to the pixel sensor 310 are placed on the back side 302B of the substrate 302 above the pixel sensor 310. Additionally, in some embodiments, a low-n structure 340 is disposed between the color filters 350. As mentioned above, the low-n structure 340 includes a grid structure and the color filters 350 are located within the grid. Therefore, the low-n structure 340 surrounds the color filters 350 and separates the color filters 350 from each other, as... Figure 8 As shown in the diagram, the low-n structure 340 can be a composite structure comprising multiple layers with a refractive index lower than that of the color filter 350. Due to its low refractive index, the low-n structure 340 acts as a light guide to direct or reflect light to the color filter 350. Therefore, the low-n structure 340 effectively increases the amount of light incident on the color filter 350. Additionally, due to its low refractive index, the low-n structure 340 provides optical isolation between adjacent color filters 350.

[0045] Color filters 350 assign light of a corresponding color or wavelength and are configured to filter out all light except for the assigned color or wavelength. More importantly, each of the color filters 350 includes multiple microstructures 332, such as... Figure 8 As shown above, various types of microstructures 332 can be obtained by modifying the operations used to form the microstructures 332. Various microstructures 332 in the color filter 350 will be further described according to one or more embodiments.

[0046] Figures 9 to 10 This is a partially enlarged view of a BSI image sensor 300 according to one or more embodiments. As mentioned above, each of the pixel sensors 310 of the BSI image sensor 300 includes a plurality of microstructures 330 formed above the back side 302B of the substrate 302. In some embodiments, the microstructures 330 include a corrugated pattern in the cross-sectional view, such as... Figures 9 to 10 As shown in the figure. In some embodiments, the sidewalls of the microstructure 330 include at least an angle θ1 with the horizontal direction of the substrate. As mentioned above, the angle θ1 is related to the refractive index of the microstructure 330. For example, when the refractive index of the microstructure 330 is about 3.6, the angle θ1 is between about 48° and about 58°, as shown in the figure. Figures 9 to 10 As shown in the diagram, but not limited thereto. As mentioned above, light will be tilted to approximately 40° after passing through microstructure 330. Furthermore, the light angle increases with the refractive index gap between microstructure 330 and dielectric layer 308. In some embodiments, microstructure 330 may include a corrugated pattern in cross-sectional views, such as... Figures 3 to 5 The details shown are omitted for simplicity.

[0047] As mentioned above, each of the pixel sensors 310 in the BSI image sensor 300 includes a plurality of microstructures 334 formed above the front side 302F of the substrate 302. In some embodiments, the microstructures 334 can be formed by operations similar to those used to form the microstructures 330, and therefore those details are omitted for brevity. Various types of microstructures 334 can be obtained by modifying the operations used to form the microstructures 334. In some embodiments, the microstructures 334 include a corrugated pattern in the cross-sectional view, such as... Figures 9 to 10 As shown in the figure. In some embodiments, the sidewalls of the microstructure 334 include at least an angle θ3 with the horizontal direction of the substrate. The angle θ3 is related to the refractive index of the microstructure 334. For example, when the refractive index of the microstructure 334 is about 3.6, the angle θ3 is between about 48° and about 58°, as illustrated in the figure. Figures 9 to 10 This disclosure is shown in the document, but is not limited thereto.

[0048] As mentioned above, each of the color filters 350 includes a plurality of microstructures 332 formed on the back side 302B of the substrate 302 above the pixel sensor 310. In some embodiments, the microstructures 332 can be formed by the operations described above, and details are therefore omitted for brevity. By modifying the operations used to form the microstructures 332, various types of microstructures 332 can be obtained, such as Figures 9 to 10 As shown in the figure. In some embodiments, the microstructure 332 includes a corrugated pattern in the cross-sectional view, such as... Figures 9 to 10 As shown in the figure. In some embodiments, at least one sidewall of one of the microstructures 332 includes an angle θ2 with respect to the horizontal direction of the substrate. As mentioned above, the angle θ2 is related to the refractive index of the color filter 350. For example, when the refractive index of the color filter 350 is about 1.6, the angle θ2 is between about 35° and about 55°, as shown in the figure. Figure 9 As shown, but not limited thereto. As mentioned above, light will be tilted to approximately 20° after passing through microstructure 332. Furthermore, the light angle increases with the refractive index of color filter 350. As mentioned above, in some embodiments, the top surface of low-n structure 340 is located between the topmost portion of microstructure 332 and the bottom surface of color filter, such as... Figure 9 As shown in the figure. In some embodiments, the sidewalls of the microstructure 332 have two different included angles θ2 and θ2' with the substrate in the horizontal direction, and at least the included angle θ2 is between about 35° and about 55°, as illustrated in the figure. Figures 9 to 10 As shown in the illustrations, but not limited thereto. In some embodiments, the microstructure 332 may include a corrugated pattern in the cross-sectional view, such as... Figures 3 to 5 The details shown are omitted for simplicity.

[0049] See Figure 11 In some embodiments, the operations used to form the microstructures 330 can be modified. For example, rounding or tapering operations are not performed, causing the microstructures 330 to be spaced apart from each other. In other words, the microstructures 330 are discrete structures, such as... Figure 11 As shown in the figure. In some embodiments, the width "b" of the microstructure 330 is between about 0.3 μm and about 0.6 μm, the spacing width "e" between the microstructures 330 is between about 0.3 μm and about 0.6 μm, and the height "h1" of the microstructure 330 is between about 0.2 μm and about 0.7 μm, but this disclosure is not limited thereto. Additionally, in some embodiments of this disclosure, the top surface of the DTI structure 304 is located between the bottom surface of the microstructure 330 and the bottom surface of the color filter 350, such as... Figure 11 As shown in the image.

[0050] See Figure 11In some embodiments, the operations used to form the microstructure 334 may be modified. For example, a rounding or tapering operation may not be performed, causing the microstructures 334 to be spaced apart from each other. In other words, the microstructures 334 are discrete structures. In some embodiments, the spacing width “c” between the microstructures 334 is between about 0.2 μm and about 0.6 μm, and the width “f” of the microstructure 334 is between about 0.2 μm and about 0.6 μm. The height h1 of the microstructure 330 is greater than the height “h3” of the microstructure 334. In some embodiments, the height h3 of the microstructure 334 is between about 0.05 μm and about 0.2 μm, but this disclosure is not limited thereto.

[0051] See also Figure 11 In some embodiments, the operations used to form the microstructures 332 are modified. For example, omitting the heat reflow operation causes the microstructures 332 to be spaced apart from each other, such as... Figure 11 As shown in the figure. In other words, microstructure 332 is a discrete structure. In some embodiments, the width "a" of microstructure 332 is between about 0.3 μm and about 0.6 μm, the spacing width "d" between microstructures 332 is between about 0.3 μm and about 0.6 μm, and the height "h2" of microstructure 332 is between about 0.2 μm and about 0.6 μm, but this disclosure is not limited thereto. In some embodiments, the height h2 of microstructure 332 is smaller than the height h1 of microstructure 330, but this disclosure is not limited thereto.

[0052] It should be noted that various microstructures 330, 332, and 334 can be formed independently. Therefore, the various microstructures 330, 332, and 334 can have any combination. For example, in some embodiments, the pixel sensor 310 may include continuous or joined microstructures 330 and 334, and the color filter 350 may include continuous or joined microstructures 332, such as... Figures 8 to 10 As shown in the figure. In some embodiments, pixel sensor 310 may include discrete microstructures 330 and 334, and color filter 350 may include discrete microstructure 332, such as Figure 11 As shown in the figure. In some embodiments, the pixel sensor 310 may include a continuous or bonded microstructure 330 above the back side 302B, and the color filter 350 may include a continuous or bonded microstructure 332, while the microstructure 334 above the front side 302F of the substrate 302 is a discrete structure, such as Figure 12 This disclosure is shown in the document, but is not limited thereto.

[0053] Return to view Figure 8Due to the microstructure 332 of the color filter 350, the light entering the color filter 350 is diffused, thus achieving a longer light travel distance. More importantly, microlenses are no longer needed in the BSI image sensor 300 because the color filter 350 containing the microstructure 332 acts as a color lens. Therefore, the height of the optical stack is reduced and the angular response is improved. See still Figure 8 Due to the microstructures 332 of the color filter 350 and the pixel sensor 310, light is diffused within the color filter 350 and the photodiode 312. Furthermore, when entering the photodiode 312, the incident light is tilted or angled through the microstructures 330 and 332, thus achieving a longer light travel distance. This increases the absorption rate of the photodiode 312. Additionally, the microstructure 334 formed above the front side 302F of the substrate 302 improves light reflection from the photodiode 312, and light can also be reflected back to the photodiode 312 through the DTI structure 304, thus creating a resonant cavity and trapping light within the photodiode 312. Therefore, more photons are absorbed, improving the sensitivity of the BSI image sensor 300. Furthermore, the extended light travel distance allows for a reduction in the thickness of the photodiode 312 or the substrate 302, further simplifying and improving the manufacturing process.

[0054] This disclosure provides a BSI image sensor that includes a color filter with microstructures, thereby allowing the removal of microlenses and reducing the height of the optical stack. More importantly, the reduced height improves angular response. This disclosure further provides a BSI image sensor that includes a thin photodiode with microstructures positioned above the front and / or back sides, thus generating a longer light travel distance within the photodiode and allowing light to be reflected back to the photodiode. In other words, light is trapped within the thinner photodiode, thereby improving the sensitivity of the pixel sensor.

[0055] In some embodiments, a BSI image sensor is provided. The BSI image sensor includes: a substrate having a front side and a back side opposite the front side; a plurality of pixel sensors disposed in the substrate; an isolation structure disposed in the substrate; a plurality of color filters disposed above the pixel sensors; and a plurality of microlenses disposed above the color filters. Each of the pixel sensors includes a photosensing device and a plurality of microstructures disposed above the back side of the substrate. The microstructures and photosensing device of one of the pixel sensors are isolated from the microstructures and photosensing devices of adjacent pixel sensors by the isolation structure.

[0056] In some embodiments, a BSI image sensor is provided. The BSI image sensor includes: a substrate having a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate; and a color filter disposed above the pixel sensor. The pixel sensor includes a plurality of first microstructures disposed above the back side of the substrate, and the color filter includes a plurality of second microstructures disposed above the back side of the substrate.

[0057] In some embodiments, a BSI image sensor is provided. The BSI image sensor includes: a substrate having a front side and a back side opposite the front side; a pixel sensor disposed in the substrate; and a color filter disposed above the pixel sensor. The pixel sensor includes a plurality of first microstructures disposed above the back side of the substrate and a plurality of second microstructures disposed above the front side of the substrate. The color filter includes a plurality of third microstructures disposed above the back side of the substrate.

[0058] The foregoing summary of features of several embodiments enables those skilled in the art to preferably understand aspects of this disclosure. Those skilled in the art will understand that this disclosure can be readily used as a basis for designing or modifying other processes and structures to achieve the same purposes and / or advantages of the embodiments introduced herein. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made herein without departing from the spirit and scope of this disclosure.

[0059] Symbol Explanation

[0060] 100 Backside Illumination (BSI) Image Sensor

[0061] 102 substrate

[0062] 102B Dorsal side

[0063] 102F Front

[0064] 104 Deep Trench Isolation (DTI) Structure

[0065] 104c coating

[0066] 106 Anti-reflective coating (ARC)

[0067] 108 dielectric layer

[0068] 109 Coating

[0069] 110 pixel sensor

[0070] 112 Photodiode

[0071] 120 Back-End Process (BEOL) Metallization Stack / Metallization Structure

[0072] 122 Metallization layer

[0073] 124 interlayer dielectric (ILD) layers

[0074] 130 microstructure

[0075] 140 Low n structure

[0076] 150 color filter

[0077] 160 microlenses

[0078] 200 Backside Illumination (BSI) Image Sensor

[0079] 202 substrate

[0080] 202B Rear Side

[0081] 202F Front

[0082] 204 Deep Trench Isolation (DTI) Structure

[0083] 206 Anti-reflective coating (ARC)

[0084] 208 dielectric layer

[0085] 209 Coating

[0086] 210 pixel sensor

[0087] 212 photodiode

[0088] 220 Back-End Process (BEOL) Metallization Stack

[0089] 222 Metallization layer

[0090] 224 Interlayer Dielectric (ILD) Layer

[0091] 230 Microstructure

[0092] 230a Central Section

[0093] 230b surrounding area

[0094] 232 Microstructure

[0095] 232a Central section

[0096] 232b surrounding area

[0097] 240 Low n structure

[0098] 250 color filter

[0099] 300 Backside Illumination (BSI) Image Sensor

[0100] 302 substrate

[0101] 302B Back Side

[0102] 302F Front

[0103] 304 Deep Trench Isolation (DTI) Structure

[0104] 306 Anti-reflective coating (ARC)

[0105] 307 dielectric layer

[0106] 308 dielectric layer

[0107] 309 Anti-reflective coating (ARC)

[0108] 310 pixel sensor

[0109] 312 photodiode

[0110] 320 Back-End Process (BEOL) Metallization Stack

[0111] 322 metallization layer

[0112] 324 Interlayer Dielectric (ILD) Layer

[0113] 330 microstructure

[0114] 332 Microstructure

[0115] 334 Microstructure

[0116] 340 Low n structure

[0117] 350 color filter

[0118] Axis A

[0119] A' axis

[0120] a width

[0121] b width

[0122] c Spacing width

[0123] d Spacing width

[0124] e Spacing width

[0125] f width

[0126] h1 height

[0127] h2 height

[0128] h3 height

[0129] θ1 included angle

[0130] θ1' included angle

[0131] θ2 included angle

[0132] θ2' included angle

[0133] θ3 included angle

Claims

1. A backside illuminated BSI image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate; a photodiode including a plurality of first microstructures and a plurality of second microstructures disposed in the pixel sensor, wherein the photodiode includes a first surface facing the back side of the substrate and a second surface opposite to the first surface facing the front side of the substrate; and a color filter disposed over the pixel sensor, the color filter comprising a plurality of third microstructures disposed over the back side of the substrate; The plurality of first microstructures are placed on the first surface of the photodiode, and the plurality of second microstructures are placed on the second surface of the photodiode. 2 . The BSI image sensor according to claim 1 , wherein a sidewall of the first microstructure and a horizontal direction of the substrate include at least a first angle, and the first angle is between 48° and 58°. 3 . The BSI image sensor according to claim 1 , wherein a sidewall of the second microstructure and a horizontal direction of the substrate include at least a second angle, and the second angle is between 48° and 58°. 4 . The BSI image sensor according to claim 1 , wherein a sidewall of the third microstructure and a horizontal direction of the substrate comprise at least one third angle, and the third angle is between 35° and 55°. 5 . The BSI image sensor according to claim 1 , wherein a height of the first microstructure is greater than a height of the second microstructure. 6 . The BSI image sensor of claim 1 , wherein the first microstructures are spaced apart from each other, the second microstructures are spaced apart from each other, and the third microstructures are spaced apart from each other.

7. A backside illuminated BSI image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a pixel sensor disposed in the substrate, the pixel sensor comprising a plurality of first microstructures disposed over the back side of the substrate; and a color filter disposed over the pixel sensor, wherein the color filter comprises a plurality of second microstructures disposed over the back side of the substrate, Each of the first microstructures has a first height, each of the second microstructures has a second height, and the second height is smaller than the first height. 8 . The BSI image sensor according to claim 7 , wherein a sidewall of the first microstructure and a horizontal direction of a substrate include at least a first angle, and a sidewall of the second microstructure and the horizontal direction of the substrate include at least a second angle. 9 . The BSI image sensor according to claim 8 , wherein the first angle and the second angle are different from each other. 10 . The BSI image sensor according to claim 8 , wherein the first angle is the same as the second angle. 11 . The BSI image sensor according to claim 7 , wherein each of the first microstructures has a first width, each of the second microstructures has a second width, and the first width and the second width are between 0.3 μm and 0.6 μm. 12 . The BSI image sensor according to claim 7 , wherein a bottom surface of the second microstructure is interposed between a top surface of the color filter and a bottom surface of the color filter.

13. The BSI image sensor of claim 7, further comprising a coating extending over the entire surface of the front side of the substrate.

14. A backside illuminated (BSI) image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a photodiode, the photodiode comprising a first surface facing the back side of the substrate and a second surface opposite to the first surface; a plurality of first microstructures, wherein the first microstructures are disposed on the first surface of the photodiode; a plurality of second microstructures, wherein the second microstructures are disposed on the second surface of the photodiode; and A color filter is placed above the photodiode. 15 . The BSI image sensor according to claim 14 , wherein a sidewall of the first microstructure and a horizontal direction of the substrate comprise at least a first angle, and the first angle is between 48° and 58°. 16 . The BSI image sensor according to claim 14 , wherein a sidewall of the second microstructure and a horizontal direction of the substrate include at least a second angle, and the second angle is between 48° and 58°. 17 . The BSI image sensor according to claim 14 , wherein a height of the first microstructure is greater than a height of the second microstructure. 18 . The BSI image sensor of claim 14 , wherein the first microstructures are spaced apart from each other, and the second microstructures are spaced apart from each other. 19 . The BSI image sensor of claim 14 , wherein a bottom surface of the second microstructure is between the first surface and the second surface of the photodiode.

20. The BSI image sensor of claim 19, further comprising a dielectric layer disposed over the front side of the substrate, wherein the second microstructures are spaced apart from each other by the dielectric layer.

21. The BSI image sensor of claim 20, further comprising a coating disposed on the front side of the substrate, wherein the coating is in contact with the dielectric layer, the second microstructure, and a portion of a surface of the substrate on the front side.

22. A backside illuminated (BSI) image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a photodiode disposed in the substrate; a color filter disposed over the back side of the substrate; a plurality of first microstructures, which are placed between the photodiode and the color filter; and A plurality of second microstructures are disposed over the front side of the substrate, wherein bottom surfaces of the second microstructures are in contact with a surface of the substrate on the back side of the substrate.

23. According to the BSI image sensor according to claim 22, the sidewall of the first microstructure and the horizontal direction of the substrate include at least a first angle, and the first angle is between 48° and 58°, and the sidewall of the second microstructure and the horizontal direction of the substrate include at least a second angle, and the second angle is between 48° and 58°. 24 . The BSI image sensor of claim 22 , wherein a height of the first microstructure is greater than a height of the second microstructure. 25 . The BSI image sensor of claim 22 , wherein the first microstructures are spaced apart from each other, and the second microstructures are spaced apart from each other.

26. The BSI image sensor of claim 22, further comprising a dielectric layer disposed over the front side of the substrate, wherein the second microstructures are spaced apart from each other by the dielectric layer.

Images