Semiconductor image sensor

Abstract

The embodiment of the invention relates to a semiconductor image sensor. A backside illuminated (BSI) image sensor includes a substrate including a front side and a backside opposite the front side; a pixel sensor disposed in the substrate; and the color filter is arranged above the pixel sensor. The pixel sensor includes a plurality of first microstructures disposed over the backside of the substrate, and the color filter includes a plurality of second microstructures disposed over the backside of the substrate.

Description

[0001] Information about divisional applications

[0002] This application is a divisional application of the invention patent application with the application date of October 31, 2018, application number "201811284627.9", and invention name "Semiconductor Image Sensor". Technical Field

[0003] Embodiments of the present invention relate to a semiconductor image sensor. Background Art

[0004] Digital cameras and other imaging devices use image sensors. Image sensors convert optical images into digital data that can be represented as digital images. Image sensors include an array of pixel sensors and supporting logic circuits. The pixel sensors of the array are unit devices for measuring incident light, and the supporting logic circuits facilitate the readout of the measurement results. One type of image sensor commonly used in optical imaging devices is a backside illuminated (BSI) image sensor. BSI image sensor manufacturing can be integrated into conventional semiconductor processes to achieve low cost, small size and high integration. In addition, BSI image sensors have low operating voltage, low power consumption, high quantum efficiency, low readout noise and allow random access. Summary of the invention

[0005] Embodiments of the present invention relate to a backside illumination (BSI) image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a plurality of pixel sensors disposed in the substrate, and each of the pixel sensors comprising a light sensing device and a plurality of microstructures disposed above the light sensing device on the back side of the substrate; an isolation structure disposed in the substrate; a plurality of color filters disposed above the pixel sensors on the back side of the substrate; and a plurality of microlenses disposed above the color filters, wherein the microstructure and the light sensing device of one of the pixel sensors are isolated from the microstructure and the light sensing device of an adjacent pixel sensor by the isolation structure.

[0006] Embodiments of the present invention relate to a backside illumination (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, the color filter comprising a plurality of second microstructures disposed over the back side of the substrate.

[0007] Embodiments of the present invention relate to a backside illumination (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 plurality of second microstructures disposed over 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] When read in conjunction with the accompanying drawings, aspects of the present disclosure are best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the sizes of various features may be arbitrarily increased or reduced for clarity of discussion.

[0009] Figure 1A is a cross-sectional view of a BSI image sensor according to aspects of the present disclosure in one or more embodiments.

[0010] Figure 1B for Figure 1A A partial magnified view of a BSI image sensor.

[0011] Figure 2A is a cross-sectional view of a BSI image sensor according to aspects of the present disclosure in one or more embodiments.

[0012] Figure 2B for Figure 2A A partial magnified view of a BSI image sensor.

[0013] Figures 3 to 7 is a partially enlarged view of a BSI image sensor according to aspects of the present disclosure in some embodiments.

[0014] Figure 8 is a cross-sectional view of a BSI image sensor according to aspects of the present disclosure in one or more embodiments.

[0015] Figures 9 to 12 is a partially enlarged view of a BSI image sensor according to aspects of the present disclosure in some embodiments. DETAILED DESCRIPTION

[0016] The following disclosure provides many different embodiments or examples for implementing the different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the disclosure. Of course, these components and arrangements are only examples and are not intended to be restrictive. For example, in the following description, the formation of a first feature above or on a second feature may include an embodiment in which the first feature and the second feature are directly contacted, and may also include an embodiment in which an additional feature may be formed between the first feature and the second feature so that the first feature and the second feature may not be directly contacted. In addition, the disclosure may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0017] Additionally, for ease of description, spatially relative terms, such as "below," "beneath," "lower," "above," "upper," "on," and the like, may be used herein to describe the relationship of one element or feature to another (or multiple) element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0018] As used herein, terms such as "first," "second," and "third" describe various elements, components, regions, layers, and / or sections, which should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Unless the context clearly indicates otherwise, terms such as "first," "second," and "third" do not imply a sequence or order when used herein.

[0019] As used herein, the terms "approximately," "substantially," "substantially," and "about" are used to describe and take into account small variations. When used in conjunction with an event or circumstance, the terms may refer to situations where the event or circumstance definitely occurs as well as situations where the event or circumstance is very close to occurring. For example, when used in conjunction with a numerical value, the terms may refer to a range of variation of less than or equal to ±10% of that numerical 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, two values ​​may be considered "substantially" the same or equal if the difference between them 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%. For example, "substantially" parallel may 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, "substantially" vertical may refer to an angular 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°.

[0020] As used herein, "microstructure" refers to a concave or protruding structure made into an uneven or rough surface of a substrate or color filter. As used herein, a "groove" is a structure that is concave from the periphery or edge of another structure, and a "protrusion" is a structure that protrudes from the periphery or edge of another structure.

[0021] A BSI image sensor includes an array of pixel sensors. Typically, a BSI image sensor includes: an integrated circuit having a semiconductor substrate and photodiodes arranged within the substrate corresponding to the pixel sensors; a back-end of line (BEOL) metallization of the integrated circuit placed over the front side of the substrate; and an optical stack including color filters and microlenses corresponding to the pixel sensors placed over the back side of the substrate. As the size of BSI image sensors decreases, BSI image sensors face several challenges. One challenge of BSI image sensors is crosstalk between adjacent pixel sensors, and another challenge of BSI image sensors is light collection. As BSI image sensors become smaller and smaller, the surface area used for light collection becomes smaller and smaller, thereby reducing the sensitivity of the pixel sensors. This is problematic for low light environments. Therefore, there is a need to increase the absorption efficiency and angular response of the pixel sensors so as to improve the sensitivity of the BSI image sensors.

[0022] Therefore, the present disclosure provides a BSI image sensor including a color filter with microstructures, so that the microlens can be removed and the height of the optical stack can be reduced. More importantly, due to the reduced height, the angular response is improved. The present disclosure further provides a BSI image sensor including a thinner photodiode, the thinner photodiode having microstructures placed over the back side and / or the front side, and due to the microstructures placed over the back side, a longer light travel distance is generated in the photodiode. In other words, light is captured in the thinner photodiode, and thus the sensitivity of the pixel sensor is improved.

[0023] Figure 1A is a cross-sectional view of a BSI image sensor 100 according to aspects of the present disclosure in some embodiments, and Figure 1B for Figure 1A FIG. 1 is a partially enlarged view of the pixel sensor 110 of the BSI image sensor 100. Figure 1A and 1B, the BSI image sensor 100 includes a substrate 102, and the substrate 102 includes, for example but not limited to, a bulk semiconductor substrate such as 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 the front side 102F. The BSI image sensor 100 includes a plurality of pixel sensors 110, typically arranged within an array, each of the pixel sensors 110 including 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 are configured to accumulate charge (e.g., electrons) from photons incident thereon. In addition, a logic device (not shown) such as a transistor is placed above the substrate 102 on the front side 102F and is configured to enable readout of the photodiodes 112.

[0024] A back-end-of-line (BEOL) metallization stack 120 is placed on the front side 102F of the substrate 102. The BEOL metallization stack 120 includes a plurality of metallization layers 122 stacked in an interlayer dielectric (ILD) layer 124. One or more contacts of the BEOL metallization stack 120 are electrically connected to a logic device. In some embodiments, the ILD layer 124 may include a low-k dielectric material (i.e., a dielectric material having a dielectric constant less than 3.9) or an oxide, but the disclosure is not limited thereto. The plurality of metallization layers 122 may include a metal such as copper (Cu), tungsten (W), or aluminum (Al), but the disclosure is not limited thereto. In some embodiments, another substrate (not shown) may be placed between the metallization structure 120 and an external connector such as a ball grid array (BGA) (not shown). And the BSI image sensor 100 is electrically connected to other devices or circuits via the external connector, but the disclosure is not limited thereto.

[0025] A deep trench isolation (DTI) structure 104 is placed in the substrate 102, such as Figure 1A and 1B . In some embodiments, the DTI structure 104 may be formed by the following operations. For example, a first etch is performed from the back side 102B of the substrate 102. The first etch produces a plurality of deep trenches (not shown) surrounding the photodiodes 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 (at Figure 1B). The coating 104c may include 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 include SiO or hafnium oxide (HfO), but the present disclosure is not limited thereto. In some embodiments, the insulating material filling the deep trench may include a low-n insulating material. Then, planarization is performed to remove excess insulating material, thereby 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 in FIG. Figure 1A and 1B 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.

[0026] In some embodiments, a plurality of color filters 150 corresponding to pixel sensors 110 are placed above pixel sensors 110 on back side 102B of substrate 102. Additionally, in some embodiments, low-n structures 140 are placed between color filters 150. In some embodiments, low-n structures 140 include a grid structure and color filters 150 are located within the grid. Thus, low-n structures 140 surround each color filter 150 and separate color filters 150 from each other, such as Figure 1A and 1B . The low-n structure 140 may be a composite structure including a plurality of layers having a refractive index less than that of the color filter 150. In some embodiments, the low-n structure 140 may include a composite stack including at least a metal layer and a dielectric layer disposed over the metal layer. In some embodiments, the metal layer may include W, Cu, or AlCu. The dielectric layer includes a material having a refractive index less than that of the color filter 150 or a material having a refractive index less than that of Si, but the present disclosure is not limited thereto. Due to the low refractive index, the low-n structure 140 acts as a light guide to guide or reflect light to the color filter 150. Thus, the low-n structure 140 effectively increases the amount of light incident into the color filter 150. In addition, due to the low refractive index, the low-n structure 140 provides optical isolation between adjacent color filters 150.

[0027] Each of the color filters 150 is placed over each of the corresponding photodiodes 112. The color filters 150 are assigned to light of corresponding colors or wavelengths and are configured to filter out all but the assigned colors or wavelengths. Typically, the color filters 150 are assigned to alternate between red, green, and blue light, so that the color filters 150 include a red filter, a green filter, and a blue filter. In some embodiments, the red filter, the green filter, and the blue filter are arranged in a Bayer mosaic pattern, but the disclosure is not limited thereto.

[0028] In some embodiments, a plurality of microlenses 160 corresponding to the pixel sensors 110 are placed above the color filter 150. It should be readily understood that the position and area of ​​each microlens 160 corresponds to the position and area of ​​the color filter 150. Figure 1A and 1B As shown in .

[0029] In some embodiments, each of the pixel sensors 110 includes a plurality of microstructures 130 disposed over the back side 102B of the substrate 102, such as Figure 1A and 1B In addition, a plurality of microstructures 130 are placed above the photodiodes 112 and surrounded by the DTI structure 104. The microstructures 130 and photodiodes 112 of one pixel sensor 110 are isolated from the microstructures 130 and photodiodes 112 of adjacent pixel sensors 110 by the DTI structure 104, as shown in FIG. Figure 1A As shown in . In some embodiments, microstructure 130 may be formed by the following operations. A mask layer (not shown) is placed over the surface of substrate 102 on back side 102B, and then a patterned photoresist (not shown) is formed over the mask layer. Substrate 102 is then etched from back side 102B through the patterned photoresist and mask layer, and thus a plurality of microstructures 130 are formed over back side 102B of substrate 102 within each of pixel sensors 110. The patterned photoresist and mask layer are then removed. In some embodiments, other operations such as wet etching may be employed. As a result, the upper and lower portions of microstructure 130 are gradually narrowed or rounded to obtain a wavy pattern, such as Figure 1A and 1B In some embodiments, the sidewall of the microstructure 130 and the horizontal direction of the substrate include at least an angle θ1 (shown in Figure 1B ), and the angle θ1 is related to the material of the microstructure 130. In some embodiments, the 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 angle θ1 is between about 48° and about 58°. After passing through the microstructure 130, the light will be tilted to about 40°. In addition, the angle of light increases as the refractive index gap between the microstructure 130 and the dielectric layer 108 increases. 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 the present disclosure is not limited thereto. In addition, by modifying the operation for forming the microstructure 130, various microstructures 130 can be obtained, such as Figures 3 to 5 In addition, in some embodiments, the microstructures 130 are spaced apart from each other (eg Figure 6 Those various microstructures 130 will be further described in one or more embodiments below.

[0030] In some embodiments, an anti-reflective coating (ARC) 106 and a dielectric layer 108 are placed over the microstructure 130 at the back side 102B of the substrate 102. Figure 1B , the surface of the microstructures 130 is lined with a conformally formed ARC 106. The dielectric layer 108 fills the spaces between the microstructures 130 and provides a substantially uniform surface over the back side 102B of the substrate 102. In some embodiments, the dielectric layer 108 may, for example, include an oxide such as silicon dioxide, but the disclosure is not limited thereto. Additionally, in some embodiments, another coating 109 corresponding to the pixel sensor 110 may be placed over the front side 102F of the substrate 102 for light reflection.

[0031] See also Figure 1B , the incident light is condensed by the microlens 160 above each color filter 150 and then converged to 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. In addition, when entering the photodiode 112, the directly incident light is tilted or inclined by the microstructure 130, and thus a longer light travel distance is generated in the photodiode 112. In addition, the light can be reflected back to the photodiode 112 by the coating layer 109 and the DTI structure 104. In other words, the light is captured in the photodiode 112, and thus the sensitivity of the pixel sensor 110 is improved. In addition, since the light travel distance is extended, the thickness of the photodiode 112 or the substrate 102 can be reduced and thus the process is further simplified and improved.

[0032] Figure 2A is a cross-sectional view of a BSI image sensor 200 according to aspects of the present disclosure in some embodiments, and Figure 2B for Figure 2A FIG. 2 is a partial enlarged view of a pixel sensor 210 of a BSI image sensor 200 of FIG. 1 . It should be noted that the same elements in the BSI image sensor 100 and the BSI image sensor 200 may include 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 the front side 202F. The BSI image sensor 200 includes a plurality of pixel sensors 210, which are generally 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. In addition, logic devices, such as transistors (not shown), are placed over the front side 202F of the substrate 202 and are configured to enable readout of the photodiodes 212.

[0033] The BEOL metallization stack 220 is placed 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 an ILD layer 224. One or more contacts of the BEOL metallization stack 220 are electrically connected to a logic device. In some embodiments, another substrate (not shown) may be placed between the metallization structure 220 and an external connector such as a ball grid array (BGA) (not shown). And the BSI image sensor 200 is electrically connected to other devices or circuits via the external connector, but the disclosure is not limited thereto. The DTI structure 204 is placed in the substrate 202, such as Figure 2A and 2B . In some embodiments, the DTI structure 204 may include a low-n material having a lower refractive index than the color filter formed below. In some embodiments, the DTI structure 204 may include an insulating material with a low-n coating sandwiched between the insulating material and the substrate 202. The DTI structure 204 surrounding and between the photodiodes 212 provides optical isolation between adjacent pixel sensors 210 and the photodiodes 212, thereby acting as a substrate isolation grid and reducing crosstalk.

[0034] In some embodiments, a plurality of color filters 250 corresponding to the pixel sensors 210 are placed above the pixel sensors 210 on the back side 202B of the substrate 202. Additionally, in some embodiments, the low-n structures 240 are placed between the color filters 250. As mentioned above, the low-n structures 240 include a grid structure and the color filters 250 are located within the grid. Thus, the low-n structures 240 surround the color filters 250 and separate the color filters 250 from each other, such as Figure 2A and 2B . The low-n structure 240 may be a composite structure including a plurality of layers having a refractive index less than that of the color filter 250. Due to the low refractive index, the low-n structure 240 acts as a light guide to guide or reflect light to the color filter 250. Thus, the low-n structure 240 effectively increases the amount of light incident into the color filter 250. In addition, due to the low refractive index, the low-n structure 240 provides optical isolation between adjacent color filters 250.

[0035] In some embodiments, each of the pixel sensors 210 includes a plurality of microstructures 230 placed over the backside 202B. The microstructures 230 may be formed by the operations mentioned above, and therefore those details are omitted for brevity. As mentioned above, by modifying the operations for forming the microstructures 230, various types of microstructures 230 may be obtained. Those various microstructures 230 will be further described in one or more embodiments below. In some embodiments, the ARC 206 and / or the dielectric layer 208 are placed over the microstructures 230 at the backside 202B of the substrate 202. Figure 2A and 2B , the surface of the microstructures 230 is lined with a conformally formed ARC 206. A dielectric layer 208 fills the spaces between the microstructures 230 and provides a substantially uniform surface over the back side 202B of the substrate 202. Additionally, in some embodiments, another coating 209 corresponding to the pixel sensors 210 may be placed over the front side 202F of the substrate 202 for light reflection, such as Figure 2B As shown in .

[0036] In some embodiments, each of the color filters 250 includes a plurality of microstructures 232 formed on the back side 202B of the substrate 202 over the pixel sensor 210. The color filter 250 is assigned to light of a corresponding color or wavelength and is configured to filter out all but the light of the assigned color or wavelength. In some embodiments, the operation for forming the color filter 250 and the microstructure 232 may include, for each of the different colors in the color assignment, forming a color filter layer and patterning the color filter layer 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 thermal reflow may be performed to round or taper the patterned photoresist. Subsequently, the color filter 250 is then etched through the rounded or taper 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 above the color filter 250. In some embodiments, the photosensitive material layer and the color filter 250 may include the same material. However, in other embodiments, the photosensitive material layer and the color filter 250 may include different materials. A process such as thermal reflow may be performed to round or gradually narrow the patterned photosensitive material layer, such as Figure 2A and 2B . Thus, a plurality of microstructures 232 are obtained. In addition, by modifying those operations for forming the microstructure 232, various microstructures 232 can be formed, and various microstructures 232 of each of the color filters 250 will be further described according to one or more embodiments.

[0037] Figures 3 to 7 2 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 over the back side 202B of the substrate 202, and each of the color filters 250 includes a plurality of microstructures 232 formed over the back side 202B of the substrate 202. In some embodiments, the microstructures 230 include a corrugated pattern in a cross-sectional view, such as Figures 2A to 5In some embodiments, the sidewall of the microstructure 230 includes at least an angle θ1 with respect to the substrate horizontal direction. 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°. Figures 2A to 5 In some embodiments, the microstructure 230 may include at least one central portion 230a and a plurality of peripheral portions 230b, and the bottom width of the central portion 230a is greater than the bottom width of the peripheral portion 230b, and the heights of the microstructures 230 are the same, such as Figure 3 In addition, the sidewall of the central portion 230a includes an angle θ1 with the horizontal direction of the substrate, and the sidewall of the peripheral portion 230b includes another angle θ1' with the horizontal direction of the substrate, and the angle θ1 is different from the angle θ1', as shown in FIG. Figure 3 In some embodiments, the microstructure 230 may include at least one central portion 230a and a plurality of peripheral portions 230b, and the height of the central portion 230a is greater than the height of the peripheral portion 230b, and the bottom widths of the microstructures 230 are the same, such as Figure 4 In addition, the sidewall of the central portion 230a includes an angle θ1 with the horizontal direction of the substrate, and the sidewall of the peripheral portion 230b includes another angle θ1' with the horizontal direction of the substrate, and the angle θ1 is different from the angle θ1', as shown in FIG. Figure 4 In some embodiments, the microstructures 230 are spaced apart from each other, such as Figure 5 In other words, the microstructures 230 are discrete structures. In addition, the flat surface can be placed between adjacent microstructures 230, such as Figure 5 In addition, in some embodiments of the present disclosure, the top surface of the DTI structure 204 is between the bottom of the microstructure 230 and the bottom surface of the color filter 250, such as Figures 2A to 5 As shown in .

[0038] Return to view Figures 2A to 5 As mentioned above, each of the color filters 250 includes a plurality of microstructures 232 formed over the back side 202B of the substrate 202. In some embodiments, the microstructures 232 may include at least one central portion 232a and a plurality of peripheral portions 232b. The central portion 232a includes an isosceles triangle profile, while the peripheral portion 232b includes a non-isosceles triangle profile, such as a right triangle profile, such as Figure 2B, but the present disclosure is not limited thereto. And the bottom width of the central portion 232a is greater than the bottom width of the peripheral portion 232b. In addition, at least the sidewall of the central portion 232a and the substrate horizontal direction include an angle θ2 related to the material of the color filter 250. 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°, such as Figure 2B , but the present disclosure is not limited thereto. After passing through the microstructure 232, the light will be tilted to about 20°. In addition, the light angle increases with the refractive index of the color filter 250. In some embodiments, the sidewall of the peripheral portion 232b and the horizontal direction of the substrate include another angle θ2', and the angle θ2' is different from the angle θ2, such as Figure 2B In some embodiments, all microstructures 232 include the same bottom width and isosceles triangle profile, and the sidewalls of the microstructures 232 and the horizontal direction of the substrate include an angle θ2, such as Figure 3 and 4 In some embodiments, the top surface of low-n structure 240 is between the topmost portion of microstructure 232 and the bottom surface of the color filter, as shown in FIG. Figure 3 In some embodiments, the topmost portion of microstructure 232 of each of color filters 250 is coplanar with the top surface of low-n structure 240, and the lowest portion of microstructure 232 is between the top surface of low-n structure 240 and the bottom surface of the color filter, as shown in FIG. Figure 4 and 5 In some embodiments, the sidewall of the microstructure 232 includes two different angles θ2 and θ2' with respect to the substrate horizontal direction, and at least the angle θ2 is between about 35° and about 55°. Figure 5 However, the present disclosure is not limited thereto.

[0039] In some embodiments, the microstructures 230 may be arranged symmetrically with respect to the axis A, such as Figures 3 to 5 In some embodiments, the microstructures 232 may be arranged symmetrically with respect to the axis A', such as Figures 3 to 5 It should be understood that the arrangement of the microstructure 230 and the microstructure 232 are independent.

[0040] As mentioned above, various types of microstructures 230 and microstructures 232 may be obtained by modifying the operations used to form microstructures 230 and microstructures 232. For example, in some embodiments, rounding or tapering operations are not performed. Thus, microstructures 232 are spaced apart from each other, such as Figure 6In 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 the present disclosure is not limited thereto. Still refer to Figure 6 In some embodiments, the operation for forming the microstructure 232 is modified. For example, the heat reflow operation is not performed so that the microstructures 232 are spaced apart from each other. Figure 6 . In other words, the microstructure 232 is a discrete structure. In some embodiments, the width "a" of the microstructure 232 is between about 0.3 μm and about 0.6 μm, the spacing width "d" between the microstructures 232 is between about 0.3 μm and about 0.6 μm, and the height "h2" of the microstructure 232 is between about 0.2 μm and about 0.6 μm, but the disclosure is not limited thereto. In some embodiments, the height h2 of the microstructure 232 is less than the height h1 of the microstructure 230, but the disclosure is not limited thereto.

[0041] Please see Figure 7 It should be noted that the various microstructures 230 and the various microstructures 232 are formed independently. Therefore, the various microstructures 230 and the various microstructures 232 may 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 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 In some embodiments, the pixel sensor 210 may include a continuous or joined microstructure 230, and the color filter 250 may include a discrete microstructure 232, such as Figure 7 or vice versa.

[0042] Return to view Figure 2B Due to the microstructure 232 of the color filter 250, the light entering the color filter 250 is diffused and thus a longer light travel distance is obtained. More importantly, a microlens is no longer required in the BSI image sensor 200 because the color filter 250 including the microstructure 232 acts as a color lens. Therefore, the height of the optical stack is reduced and the angular response is improved. Still referring to Figure 2B, due to the microstructure 232 of the color filter 250 and the microstructure 230 of the pixel sensor 210, the light is diffused in the color filter 250 and the photodiode 212. In addition, when entering the photodiode 212, the directly incident light is tilted or inclined by the microstructures 230 and 232, and thus obtains a longer light travel distance. Therefore, the absorption rate of the photodiode 212 is increased. In addition, since the light can be reflected back to the photodiode 212 by the DTI structure 204 and the coating 209, it is considered that the light is trapped in the photodiode 212, as shown in FIG. Figure 2B As shown in . Therefore, more photons are absorbed and the sensitivity of the BSI image sensor 200 is improved. In addition, since the light travels a longer distance, the thickness of the photodiode 212 or the substrate 202 is reduced and thus the process is further simplified and improved.

[0043] See also Figure 8 , a cross-sectional view of a BSI image sensor 300 according to aspects of the present disclosure in some embodiments is provided. It should be noted that the same elements in the BSI image sensor 100 / 200 and the BSI image sensor 300 may include 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, and the substrate 302 has a front side 302F and a back side 302B opposite the front side 302F. The BSI image sensor 300 includes a plurality of pixel sensors 310, which are generally arranged in an array. A plurality of photodiodes 312 corresponding to the pixel sensors 310 are placed in the substrate 302. In addition, a logic device (not shown) such as a transistor is placed over the front side 302F of the substrate 302 and is configured to enable readout of the photodiodes 312.

[0044] The BEOL metallization stack 320 is placed 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 an ILD layer 324. One or more contacts of the BEOL metallization stack 320 are electrically connected to a logic device. In some embodiments, another substrate (not shown) may be placed between the metallization structure 320 and an external connector such as a ball grid array (BGA) (not shown). And the BSI image sensor 300 is electrically connected to other devices or circuits via the external connector, but the present disclosure is not limited thereto. The DTI structure 304 is placed in the substrate 302, such as Figure 8. In some embodiments, the DTI structure 304 may include a low-n material having a lower refractive index than the color filter formed below. In some embodiments, the DTI structure 304 may include an insulating material with a low-n coating sandwiched between the insulating material and the substrate 302. The DTI structure 304 surrounding and between the photodiodes 312 provides optical isolation between adjacent pixel sensors 310 and the photodiodes 312, thereby acting as a substrate isolation grid and reducing crosstalk.

[0045] In some embodiments, each of the pixel sensors 310 includes a plurality of microstructures 330 formed over the back side 302B of the substrate 302 and a plurality of microstructures 334 over the front side 302F, such as Figure 8 . In some embodiments, ARC 306 and dielectric layer 308 are placed over microstructures 330 on the back side 302B of substrate 302. As mentioned above, the surface of microstructures 330 can be lined with conformally formed ARC 306. Dielectric layer 308 fills the spaces between microstructures 330 and provides a substantially uniform surface over the back side 302B of substrate 302. In some embodiments, dielectric layer 307 and ARC 309 are placed over microstructures 334 on the front side 302F of substrate 302, as shown in FIG. Figure 8 . The dielectric layer 307 fills the spaces between the microstructures 334 and provides a substantially uniform surface over the front side 302F of the substrate 302. And the ARC 309 is formed over the uniform surface for improving light reflection. The microstructures 330 and microstructures 334 of each of the pixel sensors 310 will be further described according to one or more embodiments.

[0046] In some embodiments, a plurality of color filters 350 corresponding to pixel sensors 310 are placed above pixel sensors 310 on back side 302B of substrate 302. Additionally, in some embodiments, low-n structures 340 are placed between color filters 350. As mentioned above, low-n structures 340 include a grid structure and color filters 350 are located within the grid. Thus, low-n structures 340 surround color filters 350 and separate color filters 350 from each other, such as Figure 8 . The low-n structure 340 may be a composite structure including a plurality of layers having a refractive index less than that of the color filter 350. Due to the low refractive index, the low-n structure 340 acts as a light guide to guide or reflect light to the color filter 350. Thus, the low-n structure 340 effectively increases the amount of light incident into the color filter 350. In addition, due to the low refractive index, the low-n structure 340 provides optical isolation between adjacent color filters 350.

[0047] The color filters 350 are assigned to light of corresponding colors or wavelengths and are configured to filter out all light except the assigned colors or wavelengths. More importantly, each of the color filters 350 includes a plurality of microstructures 332, such as Figure 8 As mentioned above, by modifying the operation for forming the microstructure 332, various types of microstructures 332 will be obtained. The various microstructures 332 of each of the color filters 350 will be further described according to one or more embodiments.

[0048] Figures 9 to 10 FIG. 3 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 over the back side 302B of the substrate 302. In some embodiments, the microstructures 330 include a corrugated pattern in a cross-sectional view, such as Figures 9 to 10 In some embodiments, the sidewall of the microstructure 330 includes at least an angle θ1 with respect to the substrate horizontal direction. 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°. Figures 9 to 10 As shown in FIG. 3 , the present disclosure is not limited thereto. As mentioned above, the light will be tilted to about 40° after passing through the microstructure 330. In addition, the light angle increases as the refractive index gap between the microstructure 330 and the dielectric layer 308 increases. In some embodiments, the microstructure 330 may include a corrugated pattern in the cross-sectional view, such as Figures 3 to 5 , and those details are omitted for simplicity.

[0049] As mentioned above, each of the pixel sensors 310 of the BSI image sensor 300 includes a plurality of microstructures 334 formed over the front side 302F of the substrate 302. In some embodiments, the microstructures 334 may be formed by operations similar to those used to form the microstructures 330, and thus those details are omitted for the sake of brevity. By modifying the operations used to form the microstructures 334, various types of microstructures 334 may be obtained. In some embodiments, the microstructures 334 include a corrugated pattern in a cross-sectional view, such as Figures 9 to 10 In some embodiments, the sidewall of the microstructure 334 and the substrate horizontal direction include at least an angle θ3. 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°. Figures 9 to 10 However, the present disclosure is not limited thereto.

[0050] 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 may be formed by the operations mentioned above, and thus the details are omitted for the sake of brevity. By modifying the operations for forming the microstructures 332, various types of microstructures 332 may be obtained, such as Figures 9 to 10 In some embodiments, the microstructure 332 includes a corrugated pattern in the cross-sectional view, such as Figures 9 to 10 In some embodiments, at least one sidewall of one of the microstructures 332 includes an angle θ2 with respect to the substrate horizontal direction. 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°. Fig. 9 As shown in FIG. 3 , the present disclosure is not limited thereto. As mentioned above, the light will be tilted to about 20° after passing through the microstructure 332. In addition, the light angle increases with the refractive index of the color filter 350. As mentioned above, in some embodiments, the top surface of the low-n structure 340 is between the topmost portion of the microstructure 332 and the bottom surface of the color filter, such as Fig. 9 In some embodiments, the sidewall of the microstructure 332 includes two different angles θ2 and θ2' with respect to the horizontal direction of the substrate, and at least the angle θ2 is between about 35° and about 55°. Figures 9 to 10 In some embodiments, the microstructure 332 may include a corrugated pattern in the cross-sectional view, such as Figures 3 to 5 , and those details are omitted for simplicity.

[0051] See also Fig.11 In some embodiments, the operations used to form the microstructures 330 may be modified. For example, rounding or tapering operations are not performed so that the microstructures 330 are spaced apart from each other. In other words, the microstructures 330 are discrete structures, such as Fig.11 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 the disclosure is not limited thereto. In addition, in some embodiments of the disclosure, the top surface of the DTI structure 304 is between the bottom of the microstructure 330 and the bottom surface of the color filter 350, such as Fig.11 As shown in .

[0052] See also Fig.11, in some embodiments, the operation for forming the microstructure 334 may be modified. For example, a rounding or tapering operation is not performed so that the microstructures 334 are spaced apart from each other. In other words, the microstructure 334 is a discrete structure. 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 the present disclosure is not limited thereto.

[0053] Still viewing Fig.11 In some embodiments, the operation for forming the microstructure 332 is modified. For example, the heat reflow operation is not performed so that the microstructures 332 are spaced apart from each other. Fig.11 . In other words, the microstructure 332 is a discrete structure. In some embodiments, the width "a" of the microstructure 332 is between about 0.3 μm and about 0.6 μm, the spacing width "d" between the microstructures 332 is between about 0.3 μm and about 0.6 μm, and the height "h2" of the microstructure 332 is between about 0.2 μm and about 0.6 μm, but the disclosure is not limited thereto. In some embodiments, the height h2 of the microstructure 332 is less than the height h1 of the microstructure 330, but the disclosure is not limited thereto.

[0054] It should be noted that the various microstructures 330, the various microstructures 332, and the various microstructures 334 may be formed independently. Therefore, the various microstructures 330, the various microstructures 332, and the various microstructures 334 may 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 In some embodiments, pixel sensor 310 may include discrete microstructures 330 and 334, and color filter 350 may include discrete microstructure 332, such as Fig.11 In some embodiments, the pixel sensor 310 may include a continuous or joined microstructure 330 over the back side 302B, and the color filter 350 may include a continuous or joined microstructure 332, while the microstructure 334 over the front side 302F of the substrate 302 is a discrete structure, such as Fig.12 However, the present disclosure is not limited thereto.

[0055] Return to view Figure 8Due to the microstructure 332 of the color filter 350, the light entering the color filter 350 is diffused and thus a longer light travel distance is obtained. More importantly, a microlens is no longer required in the BSI image sensor 300 because the color filter 350 including the microstructure 332 acts as a color lens. Therefore, the height of the optical stack is reduced and the angular response is improved. Still referring to Figure 8 , due to the microstructure 332 of the color filter 350 and the microstructure 330 of the pixel sensor 310, light is diffused in the color filter 350 and the photodiode 312. In addition, when entering the photodiode 312, the incident light is tilted or inclined by the microstructure 330 and the microstructure 332, and thus a longer light travel distance is obtained. Therefore, the absorption rate of the photodiode 312 is increased. In addition, the microstructure 334 formed on the front side 302F of the substrate 302 improves the reflection of light to the photodiode 312, while the light can also be reflected back to the photodiode 312 by the DTI structure 304, thus creating a resonant cavity and capturing the light in the photodiode 312. Therefore, more photons are absorbed and the sensitivity of the BSI image sensor 300 is improved. In addition, since the light travel distance is extended, the thickness of the photodiode 312 or the substrate 302 can be reduced and thus the process is further simplified and improved.

[0056] In the present disclosure, a BSI image sensor is provided, which includes a color filter with microstructures, so that the microlens can be removed and the height of the optical stack can be reduced. More importantly, due to the reduced height, the angular response is improved. The present disclosure further provides a BSI image sensor, which includes a thinner photodiode, wherein the thinner photodiode has a microstructure placed on the front side and / or the back side, so that a longer light travel distance is generated in the photodiode and the light can be reflected back to the photodiode. In other words, the light is captured in the thinner photodiode, and the sensitivity of the pixel sensor is improved.

[0057] In some embodiments, a BSI image sensor is provided. The BSI image sensor includes: a substrate including a front side and a back side opposite to 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 light sensing device and a plurality of microstructures disposed above the back side of the substrate. The microstructure and light sensing device of one of the pixel sensors are isolated from the microstructure and light sensing device of an adjacent pixel sensor by the isolation structure.

[0058] In some embodiments, a BSI image sensor is provided. The 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.

[0059] In some embodiments, a BSI image sensor is provided. The 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 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.

[0060] The foregoing summarizes the features of several embodiments so that those skilled in the art can preferably understand the aspects of the present disclosure. Those skilled in the art will appreciate that they can readily use the present disclosure as a basis for designing or modifying other processes and structures for achieving the same purposes and / or achieving the same 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 the present disclosure, and that various changes, substitutions, and modifications may be made herein without departing from the spirit and scope of the present disclosure.

[0061] Explanation of symbols

[0062] 100 Backside Illumination (BSI) Image Sensor

[0063] 102 Substrate

[0064] 102B Back

[0065] 102F Front

[0066] 104 Deep Trench Isolation (DTI) Structure

[0067] 104c coating

[0068] 106 Anti-reflective coating (ARC)

[0069] 108 Dielectric layer

[0070] 109 Coating

[0071] 110-megapixel sensor

[0072] 112 Photodiode

[0073] 120Back-end-of-line (BEOL) metallization stack / metallization structure

[0074] 122 metallization layer

[0075] 124 interlayer dielectric (ILD) layer

[0076] 130 Microstructure

[0077] 140 low n structure

[0078] 150 Color Filters

[0079] 160 Microlenses

[0080] 200 Backside Illumination (BSI) Image Sensor

[0081] 202 Substrate

[0082] 202B Back

[0083] 202F Front

[0084] 204 Deep Trench Isolation (DTI) Structure

[0085] 206 Anti-reflective coating (ARC)

[0086] 208 dielectric layer

[0087] 209 Coating

[0088] 210-megapixel sensor

[0089] 212 Photodiode

[0090] 220 Back-end of line (BEOL) metallization stack

[0091] 222 metallization layer

[0092] 224 interlayer dielectric (ILD) layer

[0093] 230 Microstructure

[0094] 230a Central part

[0095] 230b Peripheral part

[0096] 232 Microstructure

[0097] 232a Central part

[0098] 232b Peripheral part

[0099] 240 low n structure

[0100] 250 color filters

[0101] 300 Backside Illumination (BSI) Image Sensor

[0102] 302 substrate

[0103] 302B Back

[0104] 302F front side

[0105] 304 Deep Trench Isolation (DTI) Structure

[0106] 306 Anti-reflective coating (ARC)

[0107] 307 Dielectric layer

[0108] 308 Dielectric layer

[0109] 309 Anti-Reflective Coating (ARC)

[0110] 310-pixel sensor

[0111] 312 Photodiode

[0112] 320 Back-end of Line (BEOL) Metallization Stack

[0113] 322 metallization layer

[0114] 324 Interlayer Dielectric (ILD) Layer

[0115] 330 Microstructure

[0116] 332 Microstructure

[0117] 334 Microstructure

[0118] 340 low n structure

[0119] 350 Color Filters

[0120] A axis

[0121] A' axis

[0122] a Width

[0123] b Width

[0124] c Interval width

[0125] d interval width

[0126] e Interval width

[0127] f Width

[0128] h1 Height

[0129] h2 Height

[0130] h3 Height

[0131] θ1 Angle

[0132] θ1' Angle

[0133] θ2 Angle

[0134] θ2' Angle

[0135] θ3 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 plurality of pixel sensors disposed in the substrate, and each of the pixel sensors comprises a light sensing device and a plurality of microstructures disposed over the light sensing device on the back side of the substrate; an isolation structure disposed in the substrate; a plurality of color filters including sidewalls disposed over the pixel sensors on the back side of the substrate; a grid disposed on the back side of the substrate, comprising sidewalls in contact with the sidewalls of the color filter; and A plurality of micro lenses are placed above the color filter, The microstructure and the light sensing device of one of the pixel sensors are isolated from the microstructure and the light sensing device of an adjacent pixel sensor by the isolation structure. 2 . The BSI image sensor according to claim 1 , wherein the microstructures are spaced apart from each other. 3 . The BSI image sensor of claim 1 , wherein an entire height of the sidewall of the grid extends along an entire height of the sidewall of the color filter. 4 . The BSI image sensor of claim 1 , further comprising a second coating layer extending over the entire surface of the front side of the substrate.

5. A backside illuminated BSI image sensor, comprising: a substrate comprising a front side and a back side opposite to the front side; a plurality of pixel sensors disposed in the substrate, and each of the pixel sensors comprises a light sensing device and a plurality of microstructures disposed over the light sensing device on the back side of the substrate; an isolation structure disposed in the substrate; a plurality of color filters including sidewalls disposed over the pixel sensors on the back side of the substrate; a grid disposed on the back side of the substrate, comprising sidewalls in contact with the sidewalls of the color filter; and a first coating disposed between the light sensing device and the isolation structure, The microstructure and the light sensing device of one of the pixel sensors are isolated from the microstructure and the light sensing device of an adjacent pixel sensor by the isolation structure. 6 . The BSI image sensor according to claim 5 , further comprising a dielectric layer between the microstructure and the color filter. 7 . The BSI image sensor of claim 6 , wherein the dielectric layer fills spaces between the microstructures and provides a uniform surface over the backside of the substrate. 8 . The BSI image sensor according to claim 6 , wherein an anti-reflection coating is further included between the dielectric layer and the microstructure and on a surface of the microstructure.

9. The BSI image sensor of claim 8, wherein the anti-reflective coating conformally lines a surface of the microstructure.

10. 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 on the back side of the substrate; and a color filter disposed over the pixel sensor, the color filter comprising a plurality of second microstructures disposed over the back side of the substrate; The color filter comprises a first surface facing the substrate, and a second surface opposite to the first surface; The plurality of second microstructures are placed on the second surface of the color filter.

Images