Integrated device and method of forming the same

Abstract

Some embodiments relate to an integrated device including: a substrate having a first refractive index, a first side, a second side, and a first region and a second region extending between the first and second sides; a lower insulating grid structure located within the substrate, the lower insulating grid structure having a plurality of first insulating segments arranged in a grid pattern and having a second refractive index, and extending between the first and second regions of the substrate; and an upper insulating grid structure covering the lower grid structure, including a plurality of second insulating segments, the outer walls of which are substantially aligned with the outer walls of the plurality of first insulating segments, the plurality of second insulating segments having a third refractive index greater than the second refractive index and less than the first refractive index.

Description

Prior Technology

[0001] Integrated circuits (ICs) with image sensors are widely used in modern electronic devices such as cameras and mobile phones. Image sensors use an array of photodetectors to detect images and transmit signals derived from those images to image processing circuitry. Some image sensors use multiple photodetectors for phase detection autofocus (PDAF). PDAF utilizes the difference in light absorption by adjacent photodetectors to quickly adjust the camera's focus for a sharper image. Simple Explanation of the Diagram

[0002] The various aspects of this disclosure will be best understood by reading the following detailed description in conjunction with the accompanying drawings. The drawings are provided to clearly illustrate relevant aspects of the embodiments. The drawings may illustrate the relationships between various structures and / or elements in the embodiments. It should be noted that the drawings are not necessarily drawn to scale. In some cases, the dimensions of various features may be arbitrarily increased or decreased for clarity of explanation. Figures 1A and 1B illustrate cross-sectional and top views of some embodiments of image sensors with dual material filling to reduce crosstalk. Figures 2A and 2B illustrate cross-sectional and top views of some embodiments of image sensors with dual material filling to reduce crosstalk, wherein the overlying insulating layer extends into a portion of a plurality of second segments in the upper insulating grid structure. Figures 3A and 3B illustrate cross-sectional and top views of some embodiments of image sensors with dual-material filling to reduce crosstalk, wherein an overlay insulating layer separates portions of DTI structural segments containing a material with a higher refractive index than the overlay insulating layer. Figures 4A, 4B, and 4C illustrate cross-sectional views of an image sensor containing a floating diffusion region shared by multiple transmission gate transistors. Figure 5 illustrates a top view of an image sensor with two photodetector regions below a microlens. Figure 6-14 illustrates a series of cross-sectional views of embodiments of methods for forming image sensors with dual-material filling to reduce crosstalk. Figures 15-20 illustrate a series of cross-sectional views of embodiments of methods for forming DTI structures with dual material filling, wherein a DTI structure segment extending between a first photodetector and a second photodetector is separated by a first insulating segment that is thinner than a second insulating segment located on one side of the regions of the first and second photodetectors. Figures 21-23 illustrate a series of cross-sectional views of embodiments of methods for forming DTI structures with dual-material filling, wherein an overlying insulating layer separates portions of DTI structure segments containing materials with a higher refractive index than the overlying insulating layer. Figure 24 illustrates a flowchart of some embodiments of methods for forming an image sensor with dual material filling to reduce crosstalk. Implementation

[0003] This disclosure provides numerous different embodiments or examples for implementing various features of this disclosure. Specific examples of elements and configurations are described below to simplify this disclosure. Of course, these 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 in direct contact, or embodiments where an additional feature may be formed between the first and second features, such that the first and second features may not be in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples in this disclosure. Such repetition is for the purpose of brevity and clarity and does not in itself imply a relationship between the various embodiments and / or configurations discussed.

[0004] Furthermore, to facilitate the description of the relationship between one element or feature and another shown in the figures, spatially relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein. These spatially relative terms are intended to cover different orientations of the device in use or operation, other than those depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly. In some embodiments, the terms "approximately" and / or "about" may be interpreted as meaning + / - 10% or + / - 5%, while in other embodiments, the terms "about" and / or "approximately" may be interpreted as within the normal manufacturing tolerances of a given wafer fabrication process.

[0005] It should be understood that the terms "first," "second," "third," etc., used in this written description and in the following claims are merely general identifiers for ease of explanation, used to distinguish different elements in a figure or series of figures. In themselves, these terms do not imply any temporal order or structural proximity of the elements, and are not intended to describe corresponding elements in different illustrated examples and / or examples not shown. For example, "first dielectric layer" illustrated in conjunction with the first figure may not necessarily correspond to "first dielectric layer" illustrated in conjunction with another figure, and may not necessarily correspond to "first dielectric layer" in examples not shown.

[0006] An image sensor comprises a pixel array having multiple photodetectors and multiple pixel circuits coupled to the photodetectors. The multiple photodetectors are organized into multiple columns and rows, forming a photodetector array. Multiple microlenses are arranged above the photodetector array. Image sensors designed using dual photodiodes (DPDs) or quad photodiodes (QPDs) to integrate phase detection autofocus (PDAF) have two or four photodetectors below the microlenses, respectively. Image sensors with this structure can use PDAF to assist in focusing the camera lens above the image sensor, achieving a faster focusing method than contrast phase detection techniques.

[0007] In some embodiments, when two or four photodetectors are positioned below a microlens, light guided by the microlens is focused onto a deep trench isolation (DTI) structure separating the photodetectors. The refractive index difference between the DTI structure material (e.g., silicon dioxide or the like with a refractive index of 1.48) and the substrate material (e.g., silicon or the like with a refractive index of 4.0) causes light entering the image sensor through the DTI structure to be scattered upon entering the substrate. This light scattering due to the refractive index difference leads to an increase in the amount of crosstalk between adjacent photodetectors, as photons are directed towards directions closer to the normal to the sidewalls of the DTI structure.

[0008] One approach to this problem is to remove the DTI structure portion centered under the microlens. While this reduces scattering, removing the DTI structure necessitates the use of additional methods to isolate the photodetector (e.g., ion implantation, additional high-k films, plasma doping, or similar methods) to maintain approximately the same level of isolation, thus reducing the device's full-well capacity. Furthermore, in embodiments with a thinner substrate thickness (e.g., between 3 and 4 micrometers), a more direct angle at which light passes through the substrate portion centered under the microlens may reduce the amount of red light absorbed by the photodetector, decreasing the quantum efficiency of the photodetector under the red filter. Therefore, a method is needed to reduce the scattered photons toward the DTI structure without removing the central portion of the DTI structure.

[0009] This disclosure provides a DTI structure including a first plurality of insulating segments and a second plurality of insulating segments covering the first plurality of insulating segments. A substrate surrounding the first plurality of insulating segments has a first refractive index (e.g., the substrate comprises silicon or the like, having a first refractive index of about 4.0), the first plurality of insulating segments have a second refractive index (e.g., as silicon dioxide or the like, having a second refractive index of about 1.48), and the second plurality of insulating segments have a third refractive index (e.g., a refractive index greater than 2). The first plurality of insulating segments are arranged in a grid pattern surrounding a photodetector region of the substrate. The second plurality of insulating segments are arranged in a grid pattern aligned with the grid pattern of the first plurality of insulating segments.

[0010] As the microlens guides light through the second plurality of insulating segments and into the substrate, the higher refractive index of these segments reduces photon scattering into the substrate. This reduced scattering decreases crosstalk between photodetectors while maintaining the isolation provided by the first insulating material in the DTI structure. Furthermore, since the portion of the DTI structure focused by the microlens is not removed, the quantum efficiency of the red pixel does not decrease, the full-well capacity is not reduced, and no additional fabrication steps are required to further isolate the photodetectors.

[0011] Figures 1A and 1B illustrate a cross-sectional view 100a and a top view 100b, respectively, of some embodiments of an image sensor with dual material fill to reduce crosstalk. The cross-sectional view 100a of Figure 1A is taken along line A-A' in the top view 100b of Figure 1B.

[0012] A first photodetector 102 and a second photodetector 104 are located in a first substrate region 106a and a second substrate region 106b of a substrate 106. A deep trench isolation (DTI) structure 108 separates the first photodetector 102 from the second photodetector 104. The DTI structure 108 includes a lower insulating grid structure 110 and an upper insulating grid structure 112. The lower insulating grid structure 110 includes a first plurality of insulating segments arranged in a grid pattern. The upper insulating grid structure 112 includes a second plurality of insulating segments, the outer sidewalls 113 of which are substantially aligned with the outer sidewalls 111 of the first plurality of insulating segments. In some embodiments, an anti-reflective coating 114 and an etch stop layer 116 surround the lower insulating grid structure 110 and the upper insulating grid structure 112.

[0013] The substrate 106 comprises a semiconductor material, such as silicon, germanium, silicon-germanium, sapphire, or the like. The substrate 106 has a first refractive index. In some embodiments, the lower insulating lattice structure 110 is an insulating material, such as silicon dioxide (SiO2) or the like, and has a second refractive index less than the first refractive index. In some embodiments, the upper insulating lattice structure 112 is or comprises an insulating material having a third refractive index (e.g., silicon nitride (Si3N4), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium oxide (TiO2), or the like), which is greater than the second refractive index and less than the first refractive index. In some embodiments, the third refractive index is greater than 2 (e.g., silicon nitride (Si3N4) with a refractive index of 2.046, tantalum oxide (Ta2O5) with a refractive index of 2.131, titanium oxide (TiO2) with a refractive index of 2.614, or the like).

[0014] Color filter 118 extends to cover the first light detector 102 and the second light detector 104. Furthermore, a first microlens 120 extends to cover the first light detector 102 and the second light detector 104. The first microlens 120 is configured to direct light from a first side of the focal lens to the first light detector 102 and light from a second side of the focal lens to the second light detector 104. Because the light originates from different parts of the focal lens, the received signal differences can be processed to focus the image using phase detection autofocus (PDAF).

[0015] The upper insulating grid structure 112, with a refractive index greater than 2, causes light guided through it to scatter less when entering the substrate 106 than light guided through a material with a lower refractive index. Furthermore, the DTI structure 108 extends through the focal point of the first microlens 120 (e.g., a portion of the DTI structure 108 at the focal point of the first microlens 120 is not removed to reduce scattering), resulting in the omission of additional isolation techniques in the final design, thus maintaining a higher full-well capacity than using implantation and plasma doping techniques to isolate the first photodetector 102 and the second photodetector 104. Removing the DTI structure 108 at the focal point also increases array edge channel mismatch because the DTI structure 108 reduces signal strength mismatch of photodetectors near the edges of the photodetector array by blocking light entering the first microlens 120 at an angle from reaching the wrong photodetector. The embodiment using an upper insulating lattice structure 112 with a refractive index greater than 2 results in reduced crosstalk without the known problems associated with maintaining the opening of the DTI structure 108 at the focal point of the first microlens 120. Therefore, the disclosed embodiment offers improved performance compared to other designs, and the photodetector array does not experience the additional optical side effects caused by other solutions.

[0016] In some embodiments, the plurality of first insulating segments constituting the lower insulating grid structure 110 include a first insulating segment 122 extending between the first photodetector 102 and the second photodetector 104, and the plurality of second insulating segments constituting the upper insulating grid structure 112 include a second insulating segment 124 extending directly over the top surface of the first insulating segments. In some embodiments, the upper insulating grid structure 112 further includes a third insulating segment 126 made of a third material extending to one side of the first photodetector 102 and the second photodetector 104. In a further embodiment, an upper insulating layer 128 made of the same material as the upper insulating grid structure 112 extends over a first surface of the substrate 106 and is mechanically coupled to the second insulating segment 124 and the third insulating segment 126.

[0017] As shown in the top view 100b of Figure 1B, in some embodiments, the upper insulating grid structure 112 divides the substrate 106 directly below the first microlens 120 (shown in dashed lines) into four substrate regions 130, each having a first photodetector 102 (shown in dashed lines), a second photodetector 104 (shown in dashed lines), a third photodetector 132 (shown in dashed lines), and a fourth photodetector 134 (shown in dashed lines). Other microlenses are also located on the four substrate regions within the substrate 106. Insulating segments of the DTI structure 108 extending between photodetectors below the same color filter (e.g., the first insulating segment (see 122 in Figure 1A) and the second insulating segment 124) are also referred to as internal isolation components 136. Insulating segments of the DTI structure 108 extending between photodetectors below different color filters (e.g., the third insulating segment 126) are also referred to as external isolation components 138.

[0018] Figures 2A and 2B illustrate cross-sectional views 200a and top views 200b, respectively, of some embodiments of an image sensor with dual-material filling to reduce crosstalk, wherein the overlying insulating layer extends into a portion of a plurality of second segments in the upper insulating grid structure. Cross-sectional view 200a of Figure 2A is taken along line A-A' of the top view 200b of Figure 2B. Figures 2A and 2B will be described simultaneously.

[0019] In some embodiments, the first insulating segment 122 and the second insulating segment 124 have a first thickness 202. In some embodiments, the first thickness 202 is less than half the height 203 of the upper insulating layer 128. In a further embodiment, the first thickness is less than 1 micrometer. In some embodiments, the third insulating segment has a second thickness 204 greater than the first thickness 202. Furthermore, a portion of the overlying insulating layer 206 extends into the third insulating segment 126 but not into the second insulating segment 124. The portion of the overlying insulating layer 206 extending into the third insulating segment 126 is also referred to as the insulating core.

[0020] The second thickness 204 of the third insulating segment 126 and the fourth insulating segment 208 directly below the third insulating segment 126 result in a higher degree of isolation between the photodetector below the first microlens 120 and the photodetector below the second microlens 210. Furthermore, the thicker insulating segments of the upper insulating grid structure 112 do not utilize the high refractive index material of the upper insulating grid structure 112 to reduce scattering, because the microlenses guide incident light to the thinner insulating segments (e.g., the first insulating segment 122 and the second insulating segment 124), so that the overlay insulating layer 206 extending into the third insulating segment 126 does not interfere with device operation. In this embodiment, the high refractive index material of the upper insulating grid structure 112 reduces crosstalk within the photodetector array while maintaining flexibility in the thickness of the insulating segments extending between the photodetectors below the different microlenses. This flexibility in thickness leads to performance improvements because the thickness can be optimized for isolation, device footprint, and full-well capacity (e.g., by increasing the space available for photodetectors within the substrate area).

[0021] In some embodiments, a portion of the overlying insulating layer 206 extends into the insulating segment extending between the microlenses (e.g., the third insulating segment extending between the first microlens 120 and the second microlens 210 (see FIG. 2B)). Furthermore, the insulating segments in the upper insulating grid structure 112 confined below a color filter (e.g., the internal isolation member 136, such as the second insulating segment 124 confined below the first microlens 120 by the fifth insulating segment 212 and the sixth insulating segment 214) do not have a portion of the overlying insulating layer 206 extending into them. That is, a continuous line segment (extending from B-B' in FIG. 2A) can be drawn between the lower surface 218 of the upper insulating layer 128 on the side of the second insulating segment 124 and the lower surface 218 of the upper insulating layer 128 on the opposite side of the second insulating segment 124, without passing through the overlying insulating layer 206. Furthermore, a continuous line segment (extending from C-C' in FIG2A) drawn between the lower surface 218 of the upper insulating layer 128 on one side of the third insulating segment 126 and the lower surface 218 of the upper insulating layer 128 on the opposite side of the third insulating segment 126 will pass through the overlying insulating layer 206.

[0022] Figures 3A and 3B illustrate cross-sectional views 300a and top views 300b of some embodiments of an image sensor with dual-material filling to reduce crosstalk, wherein an overlying insulating layer separates portions of a DTI segment having a material with a higher refractive index than the overlying insulating layer. Cross-sectional view 300a of Figure 3A is taken along line A-A' of top view 300b of Figure 3B. Figures 3A and 3B will be described simultaneously.

[0023] In some embodiments, the insulating segments (see 112 in FIG. 1B) comprising the material of the upper insulating grid structure do not extend in a grid pattern. Instead, the insulating segments (e.g., the second insulating segment 124 and the seventh insulating segment 302) extend directly to cover portions of the lower insulating grid structure 110 that correspond to the focal points of the plurality of microlenses and the intersections of the lower insulating grid structure located below the central portions of the plurality of microlenses. For example, the second insulating segment 124 and the first portion 128a of the upper insulating layer 128 cover a portion of the lower insulating grid structure 110 located directly below the central portion 304 of the first microlens 120, while the seventh insulating segment 302 comprising the same material as the second insulating segment and the second portion 128b of the upper insulating layer 128 cover a portion of the lower insulating grid structure 110 located below the central portion 306 of the second microlens 210.

[0024] The insulating segment below the first microlens 120, containing a high-refractive-index material (e.g., the same material as the upper insulating grid structure (see 112 in FIG. 1B)), and the insulating segment below the second microlens 210, containing a high-refractive-index material (e.g., the same material as the upper insulating grid structure (see 112 in FIG. 1B)), are separated by the lower insulating grid structure 110 (see FIG. 3B). A portion of the upper insulating layer 128 below the first microlens 120 (e.g., the first portion 128a) and a portion of the upper insulating layer 128 below the second microlens (e.g., the second portion 128b) are separated by the overlying insulating layer 206. The selective placement of the high-refractive-index material at the microlens focal point ensures that the insulating segment around the photodetector corresponding to the microlens is not affected by the high-refractive-index material forming process, thereby providing greater flexibility in forming the DTI structure 108. Furthermore, the embodiments represented by Figures 3A and 3B retain the optical properties of the material selected for the DTI structure 108 surrounding the photodetector corresponding to the first microlens 120, as well as the optical properties of the overlying insulating layer 206 outside the central portion 304 of the first microlens 120.

[0025] As shown in the top view 300b of Figure 3B, in some embodiments, the first insulating segment 122 has a first length 308 and is confined between the fifth insulating segment 212 and the sixth insulating segment 214 of the lower insulating grid structure 110. In a further embodiment, the second insulating segment 124 has a second length 310 and is confined between the inner sidewalls of the first insulating segment 122, wherein the second length 310 is less than the first length 308. In some embodiments, the insulating segment comprising a high refractive index material is located directly above each odd-numbered intersection of the DTI structure (see 108 in Figure 3B) in the first direction 312 and the second direction 314 perpendicular to the first direction. In some embodiments, the first insulating segment 122 is bisected by a vertical insulating segment 316 extending in the second direction 314.

[0026] Figures 4A, 4B, and 4C illustrate cross-sectional views 400a, 400b, and 400c of an image sensor containing floating diffusion regions shared among multiple transfer transistors. Figures 4A, 4B, and 4C are described simultaneously. Figures 4A, 4B, and 4C illustrate a DTI structure 108 having the features shown in Figures 1A, 2A, and 3A, wherein a portion of the lower insulating grid structure 110 directly below the central portion 304 of the first microlens 120 and the central portion 306 of the second microlens 210 directly covers a portion of the substrate 106 and the floating diffusion regions 402. The floating diffusion regions 402 are coupled to circuitry of the image sensor, such as pixel circuitry and image signal processor (ISP) circuitry. The floating diffusion regions 402 are coupled to an interconnect structure 404. The interconnect structure 404 is further coupled to multiple transfer transistors 406. Multiple transmission gate transistors 406 are configured to form a conductive channel between the photodetector array and the floating diffusion region 402, so that charge from the photodetector array is transferred to the pixel circuit.

[0027] Figure 5 illustrates a top view 500 of an image sensor having two photodetector regions located below a microlens. As shown in the top view of Figure 5, in some embodiments, two substrate regions 106a and 106b are located directly below the first microlens 120 (shown in dashed lines), containing a first photodetector 102 and a second photodetector 104, respectively. The second insulating segment 124 of the upper insulating grid structure 112 is not bisected by an additional segment directly below the first microlens 120. In other embodiments (see Figures 1B, 2B, and 3B), four substrate regions 130 are isolated from each other by the DTI structure 108 and located directly below the first microlens 120, wherein the four substrate regions 130 are isolated by a first insulating segment (see 122 in Figure 1A), a second insulating segment 124, and a vertical insulating segment (see 316 in Figure 3B), which intersects the first insulating segment (see 122 in Figure 1A) and the second insulating segment 124 at the midpoint between the four substrate regions 130.

[0028] Figures 6-14 illustrate a series of cross-sectional views 600-1400 of some embodiments of a method for forming an image sensor with dual material filling to reduce crosstalk. Although Figures 6-14 are depicted as a series of actions, it should be understood that these actions are not limiting, as the order of actions may be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some actions illustrated and / or described may be omitted in whole or in part.

[0029] As shown in the cross-sectional view 600 of FIG6, a plurality of photodetectors 602, including a first photodetector 102 and a second photodetector 104, are formed in a substrate 106. In some embodiments, the plurality of photodetectors 602 are or comprise an n-type region of the substrate formed using an implantation process. Furthermore, a floating diffusion region 402 is formed on a first side 106f of the substrate 106. In some embodiments, the floating diffusion region 402 is or comprises an n-type region formed using an implantation process (e.g., a substrate region with n-type doping). The substrate has a first refractive index.

[0030] As shown in the cross-sectional view 700 of Figure 7, a transmission gate transistor 406 and an interconnect structure 404 are formed on a substrate 106. The interconnect structure 404 includes one or more wire levels and one or more via levels, forming conductive paths on the substrate 106 and coupling to the transmission gate transistor 406 and the floating diffusion region 402. Furthermore, multiple interlayer dielectric layers 702 are formed between the wire levels and via levels of the interconnect structure 404. The transmission gate transistor 406 is configured to independently form a channel between the photodetectors of the multiple photodetectors 602 and the floating diffusion region of the floating diffusion region 402 when the transistor gate reaches a threshold voltage. In some embodiments, the interconnect structure 404 comprises a conductive material, such as copper, aluminum, tungsten, a conductive metal alloy, or the like. In some embodiments, the multiple interlayer dielectric layers 702 are or comprise insulating materials, such as silicon dioxide (SiO2), silicon nitride (Si3N4), or the like. The interconnect structure 404 and the transmission gate transistor 406 are formed using one or more deposition processes (e.g., physical vapor deposition (PVD), atomic layer deposition (ALD), chemical vapor deposition (CVD), or similar processes) and removal processes (e.g., dry etching, self-aligned etching, planarization process, or similar processes). In some embodiments, the interconnect structure is formed using a damascene process, a dual damascene process, or similar processes.

[0031] As shown in the cross-sectional view 800 of FIG8, in some embodiments, a first masking layer 804 is formed on a second side 106s of the substrate 106. In some embodiments, the first masking layer 804 is formed using a deposition process, a spin-on process, a dipping process, or a similar process. The first masking layer 804 is then patterned. In some embodiments, the first masking layer 804 is a photoresist and is patterned using photolithography. The openings in the first masking layer correspond to the locations of the DTI structure to be formed later (see 108 in FIG1A).

[0032] After the first mask layer 804 is patterned, a first etching process 802 is performed. In some embodiments, the first etching process 802 is an anisotropic dry etching process. The first etching process results in the formation of a plurality of first openings 806 corresponding to the locations of the DTI structure (see 108 in FIG1A).

[0033] As shown in the cross-sectional view 900 of Figure 9, an anti-reflective coating 114, an etch stop layer 116, and a first conformal insulating layer 902 are formed in a plurality of first openings 806 (shown in dashed lines). In some embodiments, the anti-reflective coating 114 is or comprises one or more of silicon dioxide (SiO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), silicon nitride (Si3N4), or the like. In some embodiments, the etch stop layer is or comprises one or more of silicon nitride (Si3N4) or the like. In some embodiments, the first conformal insulating layer 902 is or comprises an insulating material, such as silicon dioxide (SiO2) or the like. The material of the first conformal insulating layer 902 has a second refractive index, which is less than the first refractive index of the substrate 106. The anti-reflective coating 114, the etch stop layer 116, and the first conformal insulating layer 902 are formed independently using one or more of PVD, ALD, CVD, or similar processes.

[0034] As shown in the cross-sectional view 1000 of FIG. 10, a portion of the first conformal insulating layer (see 902 in FIG. 9) is removed, leaving the lower insulating grid structure 110 within the plurality of first openings 806. The upper portions of the plurality of first openings 806 and the inner sidewalls of the etch stop layer 116 are exposed. In some embodiments, a portion of the first conformal insulating layer (see 902 in FIG. 9) is removed using an etching process 1002, such as a self-aligned dry etching process or a similar process.

[0035] As shown in the cross-sectional view 1100 of Figure 11, a second conformal insulating layer 1102 is formed on the substrate 106, including an upper insulating grid structure 112 and an upper insulating layer 128. The second conformal insulating layer 1102 is or comprises an insulating material having a third refractive index greater than the second refractive index of the lower insulating grid structure 110, such as silicon nitride (Si3N4), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium dioxide (TiO2), or the like. In a further embodiment, the second conformal insulating layer 1102 is or comprises a transparent insulating material configured to allow light to pass through the upper insulating layer 128 to reach the substrate 106. The upper insulating grid structure 112 is defined as a portion of the second conformal insulating layer 1102 between the inner sidewalls of the etch stop layer 116. The upper insulating layer 128 is defined as a portion of the second conformal insulating layer 1102 covering the inner sidewalls of the etch stop layer 116. The interface 1104 between the upper insulating grid structure 112 and the upper insulating layer 128 is flush with the uppermost surface of the etch stop layer 116. In some embodiments, the second conformal insulating layer 1102 is formed using a deposition process, such as one or more of physical vapor deposition, atomic layer deposition, chemical vapor deposition, or similar methods.

[0036] As shown in the cross-sectional view 1200 of Figure 12, a third conformal insulating layer 1202 is formed on the upper insulating layer 128. The third conformal insulating layer 1202 is or contains an insulating material, such as silicon dioxide (SiO2) or the like. In some embodiments, the second conformal insulating layer 1102 is formed using a deposition process, such as one or more of physical vapor deposition, atomic layer deposition, chemical vapor deposition, or similar methods.

[0037] As shown in the cross-sectional view 1300 of Figure 13, a portion of the third conformal insulating layer (see 1202 in Figure 12) is removed, resulting in the overlying insulating layer 206 covering the upper insulating layer 128. In some embodiments, a portion of the third conformal insulating layer (see 1202 in Figure 12) is removed using a planarization process (e.g., a chemical mechanical planarization (CMP) process). The overlying insulating layer 206 has a substantially planar upper surface.

[0038] As shown in the cross-sectional view 1400 of FIG14, a plurality of color filters 1404, including a color filter 118, and a plurality of microlenses 1402, including a first microlens 120 and a second microlens 210, are formed on the upper surface of the overlying insulating layer 206. In some embodiments, the formation of the plurality of color filters 1404 is such that the color filters independently cover two different photodetectors (for example, as shown in FIG5, the color filter 118 extends directly to cover the first photodetector 102 and the second photodetector 104, but does not cover the third photodetector (see 132 in FIG1B) and the fourth photodetector (see 134 in FIG1B)). In other embodiments, the plurality of color filters 1404 are formed such that each color filter independently covers four different photodetectors (e.g., as shown in Figures 1B, 2B, and 3B, color filter 118 extends directly to cover the first photodetector 102, the second photodetector 104, the third photodetector (see 132 in Figure 1B), and the fourth photodetector (see 134 in Figure 1B)). In some embodiments, the plurality of microlenses 1402 are positioned such that each microlens is individually centered on the color filters of the plurality of color filters 1404. In other embodiments, the plurality of microlenses 1402 are offset from the center of the color filters according to their position on the photodetector array. That is, a microlens near the central portion of the photodetector array may be centered on the color filter directly below it, while a microlens near the edge of the photodetector array may be offset from the center of the color filters to more effectively capture light incident at an oblique angle.

[0039] Figures 15-20 illustrate a series of cross-sectional views 1500-2000, showing methods for forming a DTI structure with dual material filling in some embodiments, wherein a DTI segment extending between a first photodetector and a second photodetector is separated by a first insulating segment that is thinner than a second insulating segment on one side of the regions of the first and second photodetectors. While Figures 15-20 are described as a series of actions, it should be understood that these actions are not limiting; the order of actions may be changed in other embodiments, and the disclosed methods are applicable to other structures. In other embodiments, some of the illustrated and / or described actions may be omitted in whole or in part. The method shown in Figures 15-20 is performed after the steps described in relation to Figures 6 and 7, as an alternative to the steps described in relation to Figures 8-13. The method continues to perform the steps described in relation to Figure 14 after performing the steps corresponding to Figure 20.

[0040] As shown in the cross-sectional view 1500 of Figure 15, in some embodiments, a second mask layer 1502 is formed on a second side 106s of the substrate 106. In some embodiments, the second mask layer 1502 is formed using a deposition process, spin coating process, dip coating process, or similar method. The second mask layer 1502 is then patterned. In some embodiments, the second mask layer 1502 is a photoresist and is patterned using photolithography. The openings in the first mask layer correspond to the locations of the DTI structure to be formed later (see 108 in Figure 2A).

[0041] After the second mask layer 1502 is patterned, a first etching process 802 is performed. In some embodiments, the first etching process 802 is an anisotropic dry etching process. The first etching process results in the formation of a plurality of first openings 806, corresponding to the location of the DTI structure (see 108 in FIG. 2A). A first portion 806a of the plurality of first openings 806 has a first width 1504, and a second portion 806b of the plurality of first openings 806 has a second width 1506, the second width 1506 being greater than the first width 1504. The first width 1504 corresponds to the location of insulating segments extending between photodetectors directly below the same color filter (e.g., a first insulating segment (see 122 in FIG. 2A) and a second insulating segment (see 124 in FIG. 2A)), and the second width 1506 corresponds to the location of insulating segments extending between photodetectors located below different color filters (e.g., a third insulating segment (see 126 in FIG. 2A) and a fourth insulating segment (see 208 in FIG. 2A)).

[0042] As shown in the cross-sectional view 1600 of Figure 16, an anti-reflective coating 114, an etch stop layer 116, and a first conformal insulating layer 902 are formed in a plurality of first openings 806 (shown in dashed lines). In some embodiments, the anti-reflective coating 114 is or comprises one or more of silicon dioxide (SiO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), silicon nitride (Si3N4), or similar materials. In some embodiments, the etch stop layer is or comprises one or more of silicon nitride (Si3N4) or similar materials. In some embodiments, the first conformal insulating layer 902 is or comprises an insulating material, such as silicon dioxide (SiO2) or similar materials. The material of the first conformal insulating layer 902 has a second refractive index, which is less than the first refractive index of the substrate 106. The anti-reflective coating 114, the etch stop layer 116, and the first conformal insulating layer 902 are formed independently using one or more of physical vapor deposition, atomic layer deposition, chemical vapor deposition, or similar methods.

[0043] As shown in the cross-sectional view 1700 of FIG. 17, a portion of the first conformal insulating layer (see 902 in FIG. 9) is removed, leaving the lower insulating grid structure 110 within the plurality of first openings 806. The upper portions of the plurality of first openings 806 and the inner sidewalls of the etch stop layer 116 are exposed. In some embodiments, a portion of the first conformal insulating layer (see 902 in FIG. 9) is removed using an etching process 1002, such as a self-aligned dry etching process or a similar process. After the etching process 1002, the exposed portions of the first portions 806a of the plurality of first openings 806 have a width equal to the first thickness 202, and the exposed portions of the second portions 806b of the plurality of first openings 806 have a width equal to the second thickness 204.

[0044] As shown in the cross-sectional view 1800 of Figure 18, a second conformal insulating layer 1102 is formed on the substrate 106, including an upper insulating grid structure 112 and an upper insulating layer 128. The second conformal insulating layer 1102 is or comprises an insulating material having a third refractive index greater than the second refractive index of the lower insulating grid structure 110, such as silicon nitride (Si3N4), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium dioxide (TiO2), or similar materials. In a further embodiment, the second conformal insulating layer 1102 is or comprises a transparent insulating material configured to allow light to pass through the upper insulating layer 128 to reach the substrate 106. The upper insulating grid structure 112 is defined as a portion of the second conformal insulating layer 1102 located directly between the inner sidewalls of the etch stop layer 116. The upper insulating layer 128 is defined as a portion of the second conformal insulating layer 1102 covering the inner sidewalls of the etch stop layer 116. The interface 1104 between the upper insulating grid structure 112 and the upper insulating layer 128 is flush with the uppermost surface of the etch stop layer 116. In some embodiments, the second conformal insulating layer 1102 is formed using a deposition process, such as one or more of physical vapor deposition, atomic layer deposition, chemical vapor deposition, or similar methods.

[0045] An insulating segment (e.g., a second insulating segment 124) formed within a first portion 806a of a plurality of first openings 806 in the upper insulating grid structure 112 has a first thickness 202. An insulating segment (e.g., a third insulating segment 126) formed within a second portion 806b of a plurality of first openings 806 in the upper insulating grid structure 112 has a second thickness 204, which is greater than the first thickness 202, and also has an opening 1802 extending through the upper insulating layer 128 and into the insulating segment. A second conformal insulating layer 1102 has a height 203, which is more than twice the first thickness 202.

[0046] As shown in the cross-sectional view 1900 of Figure 19, a third conformal insulating layer 1202 is formed on the second conformal insulating layer 1102. The third conformal insulating layer 1202 fills the opening 1802 extending into the second conformal insulating layer 1102. The third conformal insulating layer 1202 is or contains an insulating material, such as silicon dioxide (SiO2) or a similar material. In some embodiments, the second conformal insulating layer 1102 is formed using a deposition process, such as one or more of physical vapor deposition, atomic layer deposition, chemical vapor deposition, or similar methods.

[0047] As shown in the cross-sectional view 2000 of Figure 20, a portion of the third conformal insulating layer (see 1202 in Figure 19) is removed, resulting in an overlay insulating layer 206 covering the upper insulating layer 128 and extending into the upper insulating grid structure 112. In some embodiments, a portion of the third conformal insulating layer (see 1202 in Figure 19) is removed using a planarization process (e.g., a chemical mechanical planarization process or a similar process). The overlay insulating layer 206 has a substantially flat upper surface. The method continues to follow the steps corresponding to Figure 14.

[0048] Figures 21-23 illustrate a series of cross-sectional views 2100-2300, showing methods for forming a DTI structure with dual material filling in some embodiments, wherein an overlying insulating layer separates portions of the DTI segments, these portions containing a material with a refractive index higher than that of the overlying insulating layer. While Figures 21-23 are described as a series of actions, it should be understood that these actions are not limiting, as the order of actions may be changed in other embodiments, and the disclosed methods are applicable to other structures. In other embodiments, some illustrated and / or described actions may be omitted in whole or in part. The method shown in Figures 21-23 is performed after following the steps described in relation to Figures 6-9, as an alternative to the steps described in relation to Figures 10-13, and continues following the steps described in relation to Figure 14 after performing the steps corresponding to Figure 23.

[0049] As shown in the cross-sectional view 2100 of FIG21, in some embodiments, a third masking layer 2104 is formed on the first conformal insulating layer 902. In some embodiments, the third masking layer 2104 is formed using a deposition process, a spin coating process, an immersion process, or a similar process. The third masking layer 2104 is then patterned. In some embodiments, the third masking layer 2104 is a photoresist and is patterned using a photolithography process. The openings in the third masking layer 2104 correspond to the locations of the upper insulating layer (see 128 in FIG3A) and the upper insulating segment to be formed thereafter.

[0050] After the third masking layer 2104 is patterned, a third etching process 2102 is performed. In some embodiments, the third etching process 2102 is an anisotropic dry etching process. The third etching process 2102 results in the formation of a plurality of second openings 2106, corresponding to the positions of the upper insulating layer (see 128 in FIG. 3A) and the upper insulating segments to be formed thereafter.

[0051] Following the third etching process 2102, a portion of the first conformal insulating layer 902, including the overlying insulating layer 206 and the lower insulating grid structure 110, remains on the substrate 106. The lower insulating grid structure 110 is defined as the portion of the first conformal insulating layer 902 directly located between the inner sidewalls of the etch stop layer 116. The overlying insulating layer 206 is defined as the portion of the first conformal insulating layer 902 covering the inner sidewalls of the etch stop layer 116. The interface 2108 between the lower insulating grid structure 110 and the overlying insulating layer 206 extends flush with the uppermost surface of the etch stop layer 116.

[0052] As shown in the cross-sectional view 2200 of Figure 22, a second conformal insulating layer 1102 is formed on the upper surface of the overlying insulating layer 206 and in a plurality of second openings 2106, including an upper insulating grid structure 112 and an upper insulating layer 128. The second conformal insulating layer 1102 is or includes an insulating material having a third refractive index greater than the second refractive index of the lower insulating grid structure 110, such as silicon nitride (Si3N4), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium oxide (TiO2), or the like. The upper insulating grid structure 112 is defined as the portion of the second conformal insulating layer 1102 directly located between the inner sidewalls of the etch stop layer 116. The upper insulating layer 128 is defined as the portion of the second conformal insulating layer 1102 covering the inner sidewalls of the etch stop layer 116. The interface 1104 between the upper insulating grid structure 112 and the upper insulating layer 128 extends flush with the uppermost surface of the etch stop layer 116. In some embodiments, the second conformal insulating layer 1102 is formed using a deposition process, such as one or more of PVD, ALD, CVD, or similar processes.

[0053] As shown in cross-sectional view 2300 of Figure 23, a portion of the second conformal insulating layer (see 1102 in Figure 22) is removed, resulting in the overlying insulating layer 206 surrounding and separating a portion of the upper insulating layer 128. In some embodiments, a portion of the second conformal insulating layer (see 1102 in Figure 22) is removed using a planarization process (e.g., a CMP process or a similar process). After the planarization process, the overlying insulating layer 206 and the upper insulator have substantially flat upper surfaces. The method continues to follow the steps corresponding to Figure 14.

[0054] Figure 24 illustrates a flowchart 2400 of some embodiments of a method for forming an image sensor with dual material filling to reduce crosstalk. While this method and other methods illustrated and / or described herein are illustrated as a series of actions or events, it will be understood that this disclosure is not limited to the illustrated sequence or actions. Therefore, in some embodiments, these actions may be performed in a different sequence than illustrated, and / or may be performed simultaneously. Furthermore, in some embodiments, the illustrated actions or events may be subdivided into multiple actions or events that may be performed at different times or simultaneously with other actions or sub-actions. In some embodiments, some illustrated actions or events may be omitted, and other unillustrated actions or events may be included.

[0055] In action or event 2402, multiple photodetectors and pixel circuits are formed on a substrate having a first refractive index. A drawing example illustrating this step can be found in Figures 6-7.

[0056] In action or event 2404, multiple openings are etched into the substrate, located on opposite sides of the pixel circuitry and between multiple photodetectors. A drawing example illustrating this step can be found in Figure 8.

[0057] In action or event 2406, an anti-reflective coating is formed in multiple openings. A drawing example illustrating this step can be found in Figure 9.

[0058] In action or event 2408, an etch stop layer is formed over the anti-reflective coating in multiple openings. A drawing example illustrating this step can be found in Figure 9.

[0059] In action or event 2410, a first conformal insulating layer is formed on the substrate, filling multiple openings and covering the etch stop layer, wherein the first conformal insulating layer has a second refractive index that is less than the first refractive index. A drawing example illustrating this step can be found in Figure 9.

[0060] In action or event 2412, a portion of the first conformal insulation layer is removed to expose a portion of the plurality of openings, wherein the first insulation segment remains in the substrate. A drawing example illustrating this step can be found in Figure 10.

[0061] In action or event 2414, a second conformal insulating layer is formed on the substrate and in the exposed portions of the plurality of openings. The second conformal insulating layer includes a second insulating segment and has a third refractive index that is greater than the second refractive index. A drawing example illustrating this step can be found in Figure 11.

[0062] In action or event 2416, multiple color filters are formed on the second conformal insulating layer, wherein one of the multiple color filters extends to cover multiple of the multiple photodetectors and is centered on the first insulating segment. A drawing example illustrating this step can be found in Figure 14.

[0063] In action or event 2418, multiple microlenses are formed on multiple color filters, wherein one of the microlenses extends to cover multiple photodetectors surrounding the first insulating segment. A drawing example illustrating this step can be found in Figure 14.

[0064] Some embodiments relate to an integrated device comprising: a substrate having a first refractive index, a first side, a second side, and a first region and a second region extending between the first side and the second side; a first photodetector located in the first region of the substrate, and a second photodetector located in the second region of the substrate; a lower insulating grid structure located within the substrate, the lower insulating grid structure comprising a plurality of first insulating segments arranged in a grid pattern and having a second refractive index, the plurality of first insulating segments extending between the first region and the second region of the substrate and isolating the first photodetector from the second photodetector; and an upper insulating grid structure covering the lower insulating grid structure and comprising a plurality of second insulating segments having outer walls substantially aligned with the outer walls of the plurality of first insulating segments, the plurality of second insulating segments having a third refractive index greater than the second refractive index and less than the first refractive index.

[0065] Other embodiments relate to an integrated device comprising: a substrate having a first refractive index, a first side, a first region, and a second region; a first insulating segment having a second refractive index and extending between the first region and the second region, and the first side of the substrate being spaced apart, wherein the second refractive index is less than the first refractive index; and a second insulating segment having a third refractive index and extending from the first side of the substrate into the first insulating segment within the substrate, wherein the third refractive index is greater than the second refractive index.

[0066] Other embodiments relate to a method of forming an integrated device, including: etching a plurality of openings in a substrate having a first refractive index; forming an anti-reflective coating in the plurality of openings; forming an etch stop layer on the anti-reflective coating in the plurality of openings; forming a first conformal insulating layer on the substrate, filling the plurality of openings and covering the etch stop layer, wherein the first conformal insulating layer has a second refractive index less than the first refractive index; removing a portion of the first conformal insulating layer to expose portions of the plurality of openings, wherein a first insulating segment remains in the substrate; and forming a second conformal insulating layer above the substrate and in the exposed portions of the plurality of openings, the second conformal insulating layer including a second insulating segment and having a third refractive index greater than the second refractive index.

[0067] It should be understood that the terms "first," "second," "third," etc., used in this written description and in the following claims are merely general identifiers for ease of explanation, used to distinguish different elements in a figure or series of figures. In themselves, these terms do not imply any temporal order or structural proximity of the elements, and are not intended to describe corresponding elements in different illustrated embodiments and / or embodiments not shown. For example, "first dielectric layer" illustrated in conjunction with the first figure may not necessarily correspond to "first dielectric layer" illustrated in conjunction with another figure, and may not necessarily correspond to "first dielectric layer" in embodiments not shown.

[0068] The features of the above embodiments are designed to facilitate understanding of this disclosure by those skilled in the art. Those skilled in the art should understand that this disclosure can be used as a basis to design and modify other processes and structures to achieve the same purpose and / or the same advantages of the above embodiments. Those skilled in the art should also understand that these equivalent substitutions do not depart from the spirit and scope of this disclosure, and changes, substitutions, or modifications can be made without departing from the spirit and scope of this disclosure.

[0069] 100a, 100a, 300a, 400a, 400b, 400c, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300: Cross-sectional view 100b, 200b, 300b, 500: Top-down view 2400: Flowchart 102: First photodetector 104: Second photodetector 106: Substrate 106a, 106b: Substrate region 106f: First side 106s: Second side 108: Deep trench isolation structure, DTI structure (deep trench isolation structure) 110: Lower insulative grid structure 111, 113: Outer sidewall 112: Upper insulative grid structure 114: Antireflective coating 116: Etch stop layer 118: Color filter 120: First microlens 122: First insulative segment 124: Second insulative segment 126: Third insulative segment 128: Upper insulating layer 128a, 806a: First portion 128b, 806b: Second portion 130: substrate region 132: Third photodetector 134: Fourth photodetector 136: Internal isolating segment 202: First thickness 203: Height 204: Second thickness 206: Overlying insulative layer 208: Fourth insulative segment 210: Second microlens 212: Fifth insulative segment 214: Sixth insulative segment 218: Lower surface 302: Seventh insulative segment 304, 306: Central portion 308: First length 310: Second length 312: First direction 314: Second direction 316: Perpendicular insulative segment 402: Floating diffusion region 404: Interconnect structure 406: Transfer transistor 602: Photodetector 702: Interlayer dielectric layer 802: First etching process 804: First masking layer 806, 1802, 2106: Opening 902: First conformal insulative layer 1002: Etching process 1102: Second conformal insulative layer 1104, 2108: Interface 1202: Third conformal insulative layer 1402: Microlenses 1404: Color filter 1502: Second masking layer 1504: First width 1506: Second width 2102: Third etching process 2104: Third masking layer 2402, 2404, 2406, 2408, 2410, 2412, 2414, 2416, 2418: Action or event

Claims

1. An integrated device, comprising: The substrate has a first refractive index, a first side, a second side, and a first region and a second region extending between the first side and the second side; A first photodetector is located in the first region of the substrate, and a second photodetector is located in the second region of the substrate; a lower insulating grid structure is located within the substrate, the lower insulating grid structure comprising a plurality of first insulating segments arranged in a grid pattern and having a second refractive index, the plurality of first insulating segments extending between the first region and the second region of the substrate and isolating the first photodetector from the second photodetector; The upper insulating grid structure covers the lower insulating grid structure and includes a plurality of second insulating segments, the plurality of second insulating segments having outer walls substantially aligned with the outer walls of the plurality of first insulating segments, the plurality of second insulating segments having a third refractive index greater than the second refractive index and less than the first refractive index.

2. The integrated device as described in claim 1, further comprising: Microlenses directly cover the first and second regions of the substrate; And a color filter, directly covering the first and second regions of the substrate, centered on a first insulating segment located directly between the first and second photodetectors.

3. The integrated device as claimed in claim 2, wherein the microlens has a focal point located between the first region and the second region of the substrate, and within the upper insulating grid structure or the lower insulating grid structure.

4. The integrated device as claimed in claim 1, wherein the upper insulating grid structure further includes an upper insulating layer extending from the plurality of second insulating segments over the first side of the substrate.

5. An integrated device, comprising: A substrate having a first refractive index, a first side, a first region, and a second region; A first insulating segment having a second refractive index and extending between the first region and the second region, and spaced apart from the first side of the substrate, wherein the second refractive index is less than the first refractive index; and a second insulating segment having a third refractive index and extending from the first side of the substrate into the first insulating segment within the substrate, wherein the third refractive index is greater than the second refractive index.

6. The integrated device as claimed in claim 5, wherein the third refractive index is less than the first refractive index and greater than 2, and wherein the second insulating segment is separated from the substrate by an anti-reflective coating.

7. The integrated device as described in claim 5, further comprising: Multiple external insulating components surround the first region and the second region, wherein the first insulating segment has a first thickness, and the multiple external insulating components have a second thickness greater than the first thickness.

8. The integrated device as described in claim 5, further comprising: The third insulating section extends along the second direction; And a fourth insulating segment, extending along the second direction; The first insulating segment has a first length and extends along a first direction from the third insulating segment to the fourth insulating segment, the second direction being perpendicular to the first direction; and the second insulating segment covers the central portion of the first insulating segment and has a second length less than the first length.

9. The integrated device as described in claim 5, further comprising: A first color filter covers the first region and the second region, and is centered on the second insulating segment; And a first microlens, covering the first region and the second region, centered on the second insulating segment.

10. A method of forming an integrated device, comprising: Multiple openings are etched in a substrate having a first refractive index; An anti-reflective coating is formed in the plurality of openings; An etch stop layer is formed on the anti-reflective coating within the plurality of openings; a first conformal insulating layer is formed on the substrate, filling the plurality of openings and covering the etch stop layer, wherein the first conformal insulating layer has a second refractive index less than the first refractive index; a portion of the first conformal insulating layer is removed to expose portions of the plurality of openings, wherein a first insulating segment remains in the substrate; and a second conformal insulating layer is formed above the substrate and in the exposed portions of the plurality of openings, the second conformal insulating layer including a second insulating segment and having a third refractive index greater than the second refractive index.

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