Image sensor and method of manufacturing the same

Abstract

The application discloses an image sensor and a manufacturing method thereof, and belongs to the technical field of semiconductors. The image sensor comprises a substrate, a plurality of photodiodes are arranged in the substrate at intervals; a first oxidation region and a second oxidation region are alternately arranged in the substrate between adjacent photodiodes, the first oxidation region and the second oxidation region are different in shape, and the first oxidation region and the second oxidation region are asymmetric about the photodiode; a deep trench isolation structure is arranged in the first oxidation region and the second oxidation region; a grid structure is arranged on the substrate between the photodiodes; and a light filtering structure is arranged on the photodiode. The image sensor and the manufacturing method thereof provided by the application can increase the optical path, avoid light crosstalk, effectively prevent the occurrence of light interference and refraction, and improve the color purity, near-infrared sensitivity and photoelectric conversion efficiency of the image sensor.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and specifically relates to an image sensor and its manufacturing method. Background Technology

[0002] In semiconductor devices, CMOS image sensors (Complementary Metal Oxide Semiconductor Image Sensors, CIS) can convert light signals into electrical signals and have advantages such as high integration, low power supply voltage, and low technical barriers. They are widely used in fields such as photography and videography, security systems, smartphones, fax machines, scanners, and medical electronics. For silicon-based image sensors, due to the physical properties of silicon itself, its conversion efficiency and response speed for near-infrared light greater than 1100 nm are relatively low. By using an optical modulation system (OM) combined with a deep trench isolation structure (DTI) to increase the optical path of near-infrared light through the filter and into the photodiode, the image sensor's response to near-infrared light can be improved, thereby increasing the photoelectric conversion efficiency of the image sensor. However, near-infrared light undergoes emission and refraction after passing through the OM and DTI. If two or more beams of light interfere after reflection or refraction, the purity of the image sensor will be reduced, resulting in a difference between the output electrical signal and the actual environment, thus reducing the light response accuracy of the image sensor. Summary of the Invention

[0003] The purpose of this invention is to provide an image sensor and its manufacturing method. The manufacturing method of the image sensor provided by this invention can increase the optical path and avoid light crosstalk, effectively prevent light interference and refraction, and improve the color purity, near-infrared sensitivity and photoelectric conversion efficiency of the image sensor.

[0004] To address the aforementioned technical problems, the present invention provides an image sensor, comprising:

[0005] A substrate, wherein a plurality of photodiodes are spaced apart within the substrate;

[0006] A first oxide region and a second oxide region are alternately disposed in the substrate between adjacent photodiodes. The first oxide region and the second oxide region have different shapes and are asymmetrical about the photodiode.

[0007] A deep trench isolation structure is disposed within the first oxidation zone and the second oxidation zone;

[0008] A grid structure is disposed on the substrate between the photodiodes; and

[0009] A filter structure is disposed on the photodiode.

[0010] In one embodiment of the present invention, the interfaces between the first oxide region and the second oxide region and the substrate are multiple irregular continuous arcs, and the shapes of the arcs at the interfaces between the first oxide region and the second oxide region and the substrate are different.

[0011] In one embodiment of the present invention, the materials of the first oxide region and the second oxide region are silicon oxide, and the material in the deep trench isolation structure is a high dielectric constant material.

[0012] In one embodiment of the present invention, the depths of the first oxide region and the second oxide region are equal, and the depth of the deep trench isolation structure is 70% to 90% of the depth of the first oxide region.

[0013] In one embodiment of the present invention, the image sensor further includes an optical control system, which extends from the surface of the photodiode into the photodiode, and the interface between the optical control system and the photodiode is arc-shaped.

[0014] The present invention also provides a method for manufacturing an image sensor, comprising:

[0015] A substrate is provided in which a plurality of photodiodes are disposed at intervals.

[0016] A first oxide region and a second oxide region are alternately formed in the substrate between adjacent photodiodes. The first oxide region and the second oxide region have different shapes and are asymmetrical about the photodiode.

[0017] Deep trench isolation structures are formed in the first oxidation zone and the second oxidation zone;

[0018] A grid structure is formed on the substrate between the photodiodes; and

[0019] A filter structure is formed on the photodiode.

[0020] In one embodiment of the present invention, the method for fabricating the first oxide region and the second oxide region includes:

[0021] A first photoresist layer is formed on the substrate, and a plurality of first openings are formed on the first photoresist layer, the first openings being spaced apart to expose the substrate between the photodiodes;

[0022] Using the first photoresist layer as a mask, the substrate exposed by the first opening is subjected to a first ion implantation process to form a first doped region;

[0023] Remove the first photoresist layer and form a second photoresist layer on the substrate. A plurality of second openings are formed on the second photoresist layer, and the second openings and the first openings are alternately exposed to expose the substrate between the photodiodes.

[0024] Using the second photoresist layer as a mask, a second ion implantation process is performed on the substrate exposed by the second opening to form a second doped region;

[0025] The second photoresist layer is removed, and the substrate is subjected to heat treatment. The dopant ions in the first doped region and the second doped region react with the silicon in the substrate to form a first oxide region and a second oxide region.

[0026] In one embodiment of the present invention, the first ion implantation process includes performing at least two tilt implantations on both sides of the substrate, with the angles of the two tilt implantations being unequal; the implanted ions are oxygen ions.

[0027] In one embodiment of the present invention, the second ion implantation process includes performing at least two tilt implantations on both sides of the substrate, with the angles of the two tilt implantations being unequal.

[0028] And / or, when performing the first ion implantation process and the second ion implantation process, at least one of the following parameters is different: the number of tilt implantations, the implantation angle, or the implantation dose.

[0029] In one embodiment of the present invention, the manufacturing method further includes:

[0030] Before forming the first oxide region and the second oxide region, a patterned photoresist layer is formed on the substrate, and a plurality of grooves are formed on the patterned photoresist layer. The grooves expose a portion of the photodiode, and the opening size of the grooves increases from the surface of the substrate.

[0031] Using the patterned photoresist layer as a mask, the portion of the photodiode exposed by the groove is etched to form a recess;

[0032] A first dielectric layer and a second dielectric layer are sequentially deposited in the substrate and the recess;

[0033] The first dielectric layer and the second dielectric layer are planarized to form an optical control system within the recess.

[0034] In summary, this invention provides an image sensor and its fabrication method. The unexpected technical effect of this application is that the deep trench isolation structure and the asymmetrical first and second oxide regions cause light to refract at these points, preventing light interference, increasing the optical path length, and avoiding crosstalk. This effectively prevents light interference and improves the color purity and photoelectric conversion efficiency of the image sensor. Simultaneously, it increases light reflection and refraction, especially near-infrared light, avoiding interference and refraction, enhancing isolation, improving the near-infrared sensitivity of the image sensor, and thus improving its photoelectric conversion efficiency, solving the problem of poor near-infrared light response in photodiodes. When an optical control system is provided, the reflection of near-infrared light can be further enhanced, thereby improving the photoelectric conversion efficiency of the image sensor. The deep trench isolation structure, formed within the oxide region, improves the etching selectivity and etching precision during fabrication, effectively reducing etching damage. The deep trench isolation structure, made of a high-dielectric-constant material, can serve as a near-infrared blocking layer, reducing the dark current of the image sensor. An air gap is incorporated within the deep trench isolation structure to enhance the isolation strength between photodiodes, prevent interference from parasitic light pollution, and improve the isolation effect of the deep trench isolation structure.

[0035] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the substrate and structural layer in one embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of a first photoresist layer formed on one side of the substrate relative to the structural layer in one embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the formation of the first doped region in one embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of the formation of a second photoresist layer and a second doped region in one embodiment of the present invention.

[0041] Figure 5 This is a schematic diagram illustrating the formation of a first oxidation region and a second oxidation region in one embodiment of the present invention.

[0042] Figure 6 This is a schematic diagram of forming a patterned photoresist layer in one embodiment of the present invention.

[0043] Figure 7 This is a schematic diagram of forming a deep trench in one embodiment of the present invention.

[0044] Figure 8 This is a schematic diagram of an image sensor according to an embodiment of the present invention.

[0045] Figure 9 This is a schematic diagram of a patterned photoresist layer formed on one side of the substrate relative to the structural layer, according to another embodiment of the present invention.

[0046] Figure 10 This is a schematic diagram of forming a depression in another embodiment of the present invention.

[0047] Figure 11 This is a schematic diagram of an optical control system formed in another embodiment of the present invention.

[0048] Figure 12 This is a schematic diagram of an image sensor according to an embodiment of the present invention.

[0049] Label Explanation:

[0050] 100, Substrate; 200, Structural Layer; 101, Photodiode; 120, First Photoresist Layer; 121, First Opening; 130, First Doped Region; 131, First Region; 132, Second Region; 133, Third Region; 134, Fourth Region; 140, Second Photoresist Layer; 141, Second Opening; 150, Second Doped Region; 151, First Division; 152, Second Division; 153, Third Division; 154, Fourth Division; 161, First Oxide Region ; 162, Second oxide region; 170, Patterned photoresist layer; 171, Recess; 172, Deep trench; 180, Deep trench isolation structure; 181, Air gap; 190, Grille structure; 201, Blue filter; 202, Green filter; 203, Red filter; 210, Microlens; 310, Patterned photoresist layer; 311, Groove; 312, Recess; 320, Optical control system; 321, First dielectric layer; 322, Second dielectric layer. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0053] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0054] CMOS image sensors are typical solid-state imaging sensors, typically comprising semiconductor devices such as pixel arrays, row drivers, column drivers, timing control logic, AD converters, data bus output interfaces, and control interfaces. Multiple semiconductor devices are usually integrated on a single silicon chip and isolated from each other. CMOS image sensors offer advantages such as small size, low power consumption, low cost, and mass production capabilities, and hold a large market share in the image sensor field. This invention provides an image sensor and its fabrication method that prevents light interference, further increases the optical path length, avoids light crosstalk, effectively prevents light interference, improves the color purity, near-infrared sensitivity, and photoelectric conversion efficiency of the image sensor, and solves the problem of poor near-infrared light response of photodiodes. The image sensor fabrication method provided by this invention can be applied to CMOS image sensors with different structures.

[0055] Please see Figure 1As shown, in one embodiment of the present invention, the structure and fabrication process of an image sensor are illustrated, for example, using a back-side illuminated (BSI) CMOS image sensor. First, a substrate 100 is provided. The substrate 100 can be any suitable semiconductor material, specifically, for example, silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), silicon-germanium (GeSi), sapphire, or a silicon wafer, etc., and also includes a stacked structure composed of these semiconductors, or a silicon-on-insulator, a silicon-on-insulator stacked layer, a silicon-germanium-on-insulator stacked layer, a silicon-germanium-on-insulator, or a germanium-on-insulator, etc., which can be selected according to the fabrication requirements of the image sensor. In this embodiment, the substrate 100 is, for example, a silicon wafer semiconductor substrate with an epitaxial structure, and the epitaxial structure is, for example, a homoepitaxial layer. In other embodiments, the substrate 100 can be selected from other semiconductor materials, and can be a doped or undoped semiconductor substrate.

[0056] Please see Figure 1 As shown, in one embodiment of the present invention, a plurality of photodiodes 101 and a plurality of semiconductor devices are formed on a substrate 100. The plurality of photodiodes 101 are spaced apart, and the semiconductor devices include, for example, pixel units, row drivers, column drivers, timing control logic, AD converters, data bus output interfaces, and control interfaces. Each photodiode 101 and the plurality of semiconductor devices constitute a pixel unit, forming a pixel point, and the plurality of pixel units form a two-dimensional pixel array. During the operation of the CMOS image sensor, an object is focused onto the pixel array through an imaging lens. Each photodiode 101 converts light intensity into an electrical signal, and the control circuit electrically connected to the photodiode 101 selects the pixel to be used, reading out the electrical signal from the pixel. After amplification and noise reduction processing, the electrical signal is output. The row drivers, column drivers, timing control logic, AD converters, data bus output interfaces, and control interfaces on the substrate 100 are used to control reset, integration, and readout, etc. After the semiconductor device is fabricated, multiple metal wiring layers are formed on the semiconductor device to connect it. These layers are then bonded to a carrier substrate to form a structural layer 200. The structural layer 200 includes multiple semiconductor devices, multiple metal wiring layers, and a carrier substrate. The carrier substrate can be, for example, a rigid packaging substrate, a flexible packaging substrate, or a ceramic packaging substrate, selected based on the fabrication requirements.

[0057] Please see Figures 1 to 2As shown, in one embodiment of the present invention, after forming the structural layer 200, the substrate 100 is flipped, and the substrate 100 is thinned on the side of the substrate 100 relative to the structural layer 200. The thickness of the remaining substrate 100 is selected according to the fabrication requirements. In this embodiment, for example, the substrate 100 is thinned down to the photodiode 101, exposing the doped region of the photodiode 101 within the substrate 100 and the substrate 100 between the photodiodes 101. After thinning, a first photoresist layer 120 is formed on the side of the substrate 100 relative to the structural layer 200. For example, the first photoresist layer 120 is formed on the substrate 100 using a spin coating method, and the first photoresist layer 120 is exposed and developed, etc., to form a plurality of first openings 121 on the first photoresist layer 120. The first openings 121 expose the substrate 100 between the photodiodes 101 at intervals.

[0058] Please see Figures 2 to 3 As shown, in one embodiment of the present invention, after forming the first photoresist layer 120, the substrate 100 exposed by the first opening 121 is subjected to a first ion implantation process using the first photoresist layer 120 as a mask to form a first doped region 130. In this embodiment, the first ion implantation process includes multiple ion implantations at different angles, different energies, and different doses, and the implanted ions are, for example, oxygen ions, to form first doped regions 130 with inconsistent concentrations. The implantation energy is, for example, 150 keV to 2000 keV, which can achieve an oxygen ion implantation depth of, for example, 0.1 μm to 6 μm to meet the requirements of image sensors. If a deeper trench isolation structure is required, a larger implantation energy can be selected. The implantation dose is, for example, 1 × 10⁻⁶. 16 ions / cm 2 ~1×10 20 ions / cm 2 The implantation dose of oxygen ions controls the area of ​​the subsequent oxide layer. By controlling the implantation dose of oxygen ions, the photosensitive area of ​​the photodiode is ensured. The implantation angle is, for example, the angle between the implantation direction and the substrate normal, and the implantation angle is, for example, 0~60°.

[0059] Please see Figure 3As shown, in one embodiment of the present invention, the first ion implantation process involves at least two tilt implantations on one side of the substrate 100, with the angles of the two tilt implantations being unequal. In this embodiment, four tilt implantations are used as an example. Specifically, the first ion implantation process includes a first implantation a1, a second implantation a2, a third implantation a3, and a fourth implantation a4. The implantation angle of the first implantation a1 is, for example, A1; the implantation angle of the second implantation a2 is, for example, A2; the implantation angle of the third implantation a3 is, for example, A3; and the implantation angle of the fourth implantation a4 is, for example, A4, satisfying A1>A2>A3>A4. After tilt implantation on one side of the substrate 100 is completed, the substrate 100 is rotated 180°, and tilt ion implantation is performed on the other side of the substrate 100. The number of tilt ion implantations, the dose, and the angle on both sides of the substrate 100 are, for example, the same, or they can be set to be different. In this embodiment, the first ion implantation process also includes a fifth implantation a5, with the implantation angle of the fifth implantation a5 being, for example, A5, satisfying A5 = 0°, i.e., the fifth implantation a5 is a perpendicular implantation to the substrate. In this embodiment, the first doped region 130, for example, extends from the exposed surface of the substrate 100 into the substrate 100 and includes, in sequence, a first region 131, a second region 132, a third region 133, and a fourth region 134. The first region 131, the second region 132, the third region 133, and the fourth region 134 have different shapes and occupy different areas.

[0060] Please see Figures 3 to 4 As shown, in one embodiment of the present invention, after the formation of the first doped region 130, the first photoresist layer 120 is removed, for example, by wet etching or ashing. A second photoresist layer 140 is then formed on the side of the substrate 100 opposite to the structural layer 200. For example, the second photoresist layer 140 is formed on the substrate 100 using spin coating. The second photoresist layer 140 is then exposed and developed. A plurality of second openings 141 are formed on the second photoresist layer 140. The second openings 141 expose the substrate 100 between the photodiodes 101 at intervals, and the second openings 141 do not expose the first doped region 130. That is, the second openings 141 and... Figure 2 The first opening 121 in the middle interleave exposes the substrate 100 between the photodiodes 101.

[0061] Please see Figure 4As shown, in one embodiment of the present invention, after forming the second photoresist layer 140, a second ion implantation process is performed on the substrate 100 exposed by the second opening 141 using the second photoresist layer 140 as a mask to form the second doped region 150. In this embodiment, the second ion implantation process includes multiple ion implantations at different angles, different energies, and different doses, and the implanted ions are, for example, oxygen ions, to form the second doped region 150 with inconsistent concentrations. The implantation energy is, for example, 150 keV to 2000 keV, which yields an oxygen ion implantation depth of, for example, 0.1 μm to 6 μm to meet the requirements of the image sensor. If a deeper trench isolation structure is required, a larger implantation energy can be selected. The implantation dose is, for example, 1 × 10⁻⁶. 16 ions / cm 2 ~1×10 20 ions / cm 2 The implantation dose of oxygen ions controls the area of ​​the subsequent oxide layer. By controlling the implantation dose of oxygen ions, the photosensitive area of ​​the photodiode is ensured. The implantation angle is, for example, the angle between the implantation direction and the substrate normal, and the implantation angle is, for example, 0~60°.

[0062] Please see Figure 4 As shown, in one embodiment of the present invention, the second ion implantation process involves at least two tilt implantations on one side of the substrate 100, with the angles of the two tilt implantations being unequal. In this embodiment, four tilt implantations are used as an example. Specifically, the second ion implantation process includes a first implantation b1, a second implantation b2, a third implantation b3, and a fourth implantation b4. The implantation angle of the first implantation b1 is, for example, B1; the implantation angle of the second implantation b2 is, for example, B2; the implantation angle of the third implantation b3 is, for example, B3; and the implantation angle of the fourth implantation b4 is, for example, B4, satisfying B1>B2>B3>B4. After tilt implantation is completed on one side of the substrate 100, the substrate 100 is rotated 180° in a plane, and tilt ion implantation is also performed on the other side of the substrate 100. The number of tilt ion implantations, the dose, and the angle performed on both sides of the substrate 100 can be the same, or they can be set to be different. In this embodiment, the second ion implantation process further includes a fifth implantation b5, where the implantation angle of the fifth implantation b5 is, for example, B5, satisfying that B5 is 0°, meaning the fifth implantation a5 is a perpendicular implantation to the substrate. In this embodiment, the second doped region 150, for example, extends from the exposed surface of the substrate 100 into the substrate 100, and sequentially includes a first portion 151, a second portion 152, a third portion 153, and a fourth portion 154. The first portion 151, the second portion 152, the third portion 153, and the fourth portion 154 each have different shapes and occupy different areas.

[0063] Please see Figures 3 to 4As shown, in one embodiment of the present invention, a first doped region 130 and a second doped region 150 are formed on both sides of the photodiode 101, respectively. The first doped region 130 and the second doped region 150 have the same depth, and the first doped region 130 and the second doped region 150 have different shapes, that is, the first doped region 130 and the second doped region 150 are asymmetrical about the photodiode 101. In this embodiment, during the first and second ion implantation processes, at least one parameter, such as the number of tilt implantations, the implantation angle, or the implantation dose, is different. That is, the number of tilt implantations is different between the two implantation processes, and / or the tilt implantation angle is different between the two implantation processes, and / or the tilt implantation dose is different between the two implantation processes. In this embodiment, A1≠B1, A2≠B2, A3≠B3, and A4≠B4 are satisfied, that is, the implantation angle is different, thereby forming a first doped region 130 and a second doped region 150 with different shapes. The first region 131 and the first segment 151 have different shapes and sizes, the second region 132 and the second segment 152 have different shapes and sizes, the third region 133 and the third segment 153 have different shapes and sizes, and the fourth region 134 and the fourth segment 154 have different shapes and sizes.

[0064] Please see Figures 4 to 5 As shown, in one embodiment of the present invention, after the second doped region 150 is formed, the second photoresist layer 140 is removed, for example, by wet etching or ashing. The substrate 100 is then heat-treated. Oxygen ions in the first doped region 130 and the second doped region 150 react with silicon in the substrate 100 to form silicon oxide, thereby forming a first oxide region 161 and a second oxide region 162. The first oxide region 161 and the second oxide region 162 are alternately disposed within the substrate 100 between adjacent photodiodes 101, and their depth is less than or equal to the depth of the photodiode 101. The first oxide region 161 and the second oxide region 162 have the same depth, and the interfaces between the first oxide region 161 and the second oxide region 162 and the substrate 100 are multiple irregular continuous arcs, with different shapes of the arcs at the interfaces between the first oxide region 161 and the second oxide region 162 and the substrate 100. The heat treatment temperature is, for example, 300℃~1200℃. Higher temperatures result in faster oxidation, but also more oxygen ion diffusion. When the photodiode area is large, the heat treatment temperature is, for example, 800℃~1200℃; when the photodiode area is small, the heat treatment temperature is, for example, 300℃~800℃. During the oxidation process, although some oxygen ions diffuse, the shapes of the first oxidation region 161 and the second oxidation region 162 are basically the same as the shapes of the first doped region 130 and the second doped region 150, respectively. That is, the shapes of the first oxidation region 161 and the second oxidation region 162 are different and asymmetrical about the photodiode 101. In this embodiment, the interfaces between the first oxidation region 161 and the second oxidation region 162 and the substrate 100 are, for example, at least two arc shapes.

[0065] Please see Figures 5 to 6 As shown, in one embodiment of the present invention, after forming the first oxide region 161 and the second oxide region 162, a patterned photoresist layer 170 is formed on one side of the substrate 100 opposite to the structural layer 200. For example, a photoresist layer is formed on the substrate 100 using a spin-coating method, and the photoresist layer is exposed and developed to form the patterned photoresist layer 170. The patterned photoresist layer 170 includes a plurality of recesses 171. The recesses 171 expose portions of the surfaces of the first oxide region 161 and the second oxide region 162 to define the location of the deep trench isolation structure.

[0066] Please see Figures 6 to 7 As shown, in one embodiment of the present invention, after forming the patterned photoresist layer 170, a portion of the first oxide region 161 and a portion of the second oxide region 162 are etched using the patterned photoresist layer 170 as a mask through a process of dry etching, wet etching, or a combination of dry and wet etching to form a deep trench 172. In this embodiment, for example, the deep trench 172 is formed by dry etching, and the etching gas includes, for example, one or a mixture of several of chlorine (Cl2), trifluoromethane (CHF3), difluoromethane (CH2F2), sulfur hexafluoride (SF6), or carbon tetrafluoride (CF4), or a combination of them and oxygen (O2). The deep trench 172 is formed within the first oxide region 161 and the second oxide region 162, and the depth of the deep trench 172 is, for example, 70% to 90% of the depth of the first oxide region 161 or the second oxide region 162. By forming deep trenches in the first oxide region 161 and the second oxide region 162, since the hardness of silicon dioxide is greater than that of the silicon substrate, the etching selectivity and etching precision are higher. This improves the etching selectivity and etching precision during the etching process, thereby effectively reducing etching damage.

[0067] Please see Figures 7 to 8As shown, in one embodiment of the present invention, a deep trench 172 is formed, and a dielectric material is deposited within the deep trench 172 until the dielectric material deposited within the deep trench 172 protrudes from the surface of the substrate 100. The dielectric material is then planarized, for example, using a chemical mechanical polishing (CMP) process to planarize a portion of the dielectric material until the dielectric material is flush with both sides of the substrate 100, forming a deep trench isolation structure 180. The present invention does not limit the deposition method of the dielectric material. For example, it can be formed using plasma-enhanced atomic layer deposition (PEALD), high-density plasma chemical vapor deposition (HDP-CVD), or high-aspect-ratio process chemical vapor deposition (HARP-CVD), etc., to form the corresponding dielectric material. In this embodiment, for example, plasma-enhanced atomic layer deposition is used to form the dielectric material to improve the controllability of the deposition and improve the deposition quality of the dielectric material. In one embodiment of the present invention, during the deposition of the dielectric material, an air gap 181 is formed within the dielectric material, for example, and the top of the air gap 181 is, for example, lower than the surface of the substrate 100. By setting the air gap 181, the isolation strength between photodiodes is improved, interference from parasitic light pollution is avoided, and the isolation effect of the formed deep trench isolation structure 180 is improved. The dielectric material is, for example, a high-k dielectric material, such as one or a mixture of several of the following: aluminum oxide (Al2O3), tantalum pentoxide (Ta2O5), hafnium oxide (HfO2), hafnium oxynitride (HfON), zirconium oxide (ZrO2), zirconium oxynitride (ZrON), zirconium oxynitride (ZrSiON), hafnium silicate (HfSiO), hafnium oxynitride (HfSiON), lanthanum hafnium oxynitride (HfLaON), or aluminum hafnium oxide (HfAlO), which can serve as a near-infrared blocking layer to reduce the dark current of the image sensor.

[0068] Please see Figure 8As shown, in one embodiment of the present invention, after forming the deep trench isolation structure 180, a grid structure 190 is formed on the substrate 100 between the photodiodes 101. The edges of the grid structure 190 are, for example, aligned with the edges of the photodiodes 101. The grid structure 190, for example, starting from the surface of the substrate 100, includes stacked layers of aluminum oxide, tantalum oxide, silicon dioxide, aluminum, and silicon dioxide, etc., and the thickness of each layer is designed according to fabrication requirements. When forming the grid structure 190, different material layers are deposited sequentially, followed by etching to form the grid structure 190. In other embodiments, other stacked structures can be selected for the grid structure, which are not limited here.

[0069] Please see Figure 8 As shown, in one embodiment of the present invention, after forming the grid structure 190, a filter structure is formed on the photodiode 101 between adjacent grid structures 190, and the filter structure is located on the photodiode 101. The filter structure includes, for example, multiple color filters, each color filter corresponding to one photodiode 101, and the multiple color filters form a color filter array. In this embodiment, the filter structure may include at least three primary color filters, such as a blue filter 201, a green filter 202, and a red filter 203, and the color filters can be arranged in any suitable combination. For example, the blue filter 201, green filter 202, and red filter 203 can be arranged alternately. Alternatively, a transparent filter can be provided, with the blue filter 201, green filter 202, red filter 203, and a transparent filter arranged alternately. The color filters can be polymeric materials, such as negative photoresist based on acrylic polymers, and may contain colored dyes. After the grid structure 190 is formed, a color filter can be directly vacuum-deposited between adjacent grid structures 190. When light passes through the color filter, its color can be changed, maintaining a high transmittance for a certain wavelength (color), thereby enhancing the photoelectric conversion effect.

[0070] Please see Figure 8As shown, in one embodiment of the present invention, the filter structure further includes a microlens 210. The microlens 210 is disposed on the filter sheet, and the top of the microlens 210 is an outwardly convex arc shape, which can focus the incident light onto the photodiode 101. The curvature of the filter structure surface can be changed according to the light focusing requirements to improve the photosensitivity. The microlens structure can be formed in any way, and the present invention does not impose any specific limitations. The number of photosensitive areas and filter structures can be set according to actual needs; the figures in this embodiment are only examples. When the image sensor is operating, light enters the photodiode 101 through the microlens 210. The photodiode 101 has a poor response to near-infrared light. However, the presence of the deep trench isolation structure 180, the first oxide region 161, and the second oxide region 162 causes light to refract at these points, increasing light reflection and refraction, especially in the near-infrared region. Due to the asymmetry of the structures of the first oxide region 161 and the second oxide region 162 on both sides of the photodiode 101, light interference (especially in the near-infrared region) can be prevented. This provides an adjustable structure to prevent light interference, further increasing the optical path length and avoiding crosstalk, effectively preventing light interference and improving the color purity and photoelectric conversion efficiency of the image sensor. Simultaneously, increased light reflection and refraction, especially in the near-infrared region, along with improved isolation, enhance the near-infrared sensitivity of the image sensor, thereby increasing its photoelectric conversion efficiency.

[0071] Please see Figure 9 As shown, in another embodiment of the present invention, after thinning the substrate 100, a patterned photoresist layer 310 is formed on one side of the substrate 100 relative to the structural layer 200. For example, a photoresist layer is formed on the substrate 100 using a spin-coating method, and the photoresist layer is exposed and developed to form the patterned photoresist layer 310. Multiple grooves 311 are formed on the patterned photoresist layer 310, exposing portions of the photodiode 101, for example, exposing the central region of the photodiode 101. During the exposure process, the exposure amount of the photoresist layer in different regions is controlled to form trapezoidal grooves 311, and the opening size of the grooves 311 increases from the surface of the substrate 100, meaning the opening size of the grooves 311 at the interface between the patterned photoresist layer 310 and the substrate 100 is the smallest. This application does not limit the size of the grooves 311, and the size is selected according to the fabrication requirements of the semiconductor device.

[0072] Please see Figures 9 to 10As shown, in another embodiment of the present invention, after forming the patterned photoresist layer 310, using the patterned photoresist layer 310 as a mask, the exposed portion of the photodiode 101 of the groove 311 is etched using a dry etching, wet etching, or a combination of dry and wet etching processes, forming a recess 312 in the central region of the photodiode 101. In this embodiment, the recess 312 is formed, for example, by dry etching, and the etching gas includes, for example, one or a mixture of several of chlorine, trifluoromethane, octafluoropropane (C4F8), sulfur hexafluoride, or carbon tetrafluoride, or a combination of them and oxygen. The shape of the recess 312 is, for example, arc-shaped, and the depth of the recess 312 is, for example, 10% to 80% of the depth of the photodiode 101, or, for example, 20% to 50%. If the depth is too large, it will affect the light conversion efficiency of the image sensor. By controlling the depth of the recess 312, the light conversion efficiency is ensured while performing optical control.

[0073] Please see Figures 10 to 11 As shown, in another embodiment of the present invention, after the recess 312 is formed, the patterned photoresist layer 310 is removed by wet etching or ashing. Then, an optical control system 320 is formed within the recess 312. The optical control system 320 includes a first dielectric layer 321 and a second dielectric layer 322, with the first dielectric layer 321 located between the photodiode 101 and the second dielectric layer 322. The first dielectric layer 321 is, for example, one or a mixture of several high dielectric constant materials such as aluminum oxide, tantalum pentoxide, hafnium oxide, hafnium oxynitride, zirconium oxide, zirconium oxynitride, zirconium oxynitride, hafnium silicate, hafnium oxynitride, lanthanum hafnium oxynitride, or aluminum hafnium oxide, and the thickness of the first dielectric layer 321 is, for example, 15 Å to 50 Å. The second dielectric layer 322 is, for example, silicon oxide. The first dielectric layer 321 is deposited in the recess 312 and on the substrate 100 using methods such as atomic layer deposition (ALD), metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or physical vapor deposition (PVD). The second dielectric layer 322 is deposited on the first dielectric layer 321 using methods such as chemical vapor deposition. After deposition, the second dielectric layer 322 and the first dielectric layer 321 are planarized using processes such as chemical mechanical polishing, so that the first dielectric layer 321 and the second dielectric layer 322 are flush with the substrates 100 on both sides, forming the optical control system 320. That is, the optical control system 320 extends from the surface of the photodiode 101 into the photodiode 101, and the interface between the optical control system 320 and the photodiode 101 is arc-shaped.

[0074] Please see Figures 11 to 12 As shown, in another embodiment of the present invention, after the optical control system 320 is formed, a first oxide region 161, a second oxide region 162, a deep trench isolation structure 180, a grid structure 190, and a filter structure are formed, and the preparation process and method are the same as in the previous embodiment, which will not be elaborated here. Due to the presence of the optical control system 320, the parameters during the preparation process may be finely adjusted; for example, when forming the doped region, the oxygen ion implantation dose may be, for example, 1 × 10⁻⁶. 16 ions / cm 2 ~1×10 18 ions / cm 2 The oxygen ion injection is relatively large, for example, 0~35°, to avoid affecting the optical control system 320. During heat treatment, when the area of ​​the optical control system 320 is small, the heat treatment temperature can be, for example, 800℃~1200℃, and when the area of ​​the optical control system 320 is large, the heat treatment temperature can be, for example, 300℃~800℃, to reduce the impact on the optical control system 320.

[0075] Please see Figure 12 As shown, in another embodiment of the present invention, when an optical control system 320 is provided, when the image sensor is working, the optical control system 320 can enhance the reflection of near-infrared light, thereby improving the photoelectric conversion efficiency of the image sensor. At the same time, the presence of the deep trench isolation structure 180, the first oxide region 161 and the second oxide region 162 can also avoid light interference and refraction, further enhance isolation, and increase more light reflection and refraction, thereby improving the near-infrared sensitivity of the image sensor and thus improving the photoelectric conversion efficiency of the image sensor.

[0076] In summary, this invention provides an image sensor and its fabrication method. The unexpected technical effect of this application is that the deep trench isolation structure and the asymmetrical first and second oxide regions cause light to refract at these points, preventing light interference, increasing the optical path length, and avoiding crosstalk. This effectively prevents light interference and improves the color purity and photoelectric conversion efficiency of the image sensor. Simultaneously, it increases light reflection and refraction, especially near-infrared light, avoiding interference and refraction, enhancing isolation, improving the near-infrared sensitivity of the image sensor, and thus improving its photoelectric conversion efficiency, solving the problem of poor near-infrared light response in photodiodes. When an optical control system is provided, the reflection of near-infrared light can be further enhanced, thereby improving the photoelectric conversion efficiency of the image sensor. The deep trench isolation structure, formed within the oxide region, improves the etching selectivity and etching precision during fabrication, effectively reducing etching damage. The deep trench isolation structure, made of a high-dielectric-constant material, can serve as a near-infrared blocking layer, reducing the dark current of the image sensor. An air gap is incorporated within the deep trench isolation structure to enhance the isolation strength between photodiodes, prevent interference from parasitic light pollution, and improve the isolation effect of the deep trench isolation structure.

[0077] The embodiments of the present invention disclosed above are merely illustrative of the invention. The embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An image sensor, characterized in that, include: A substrate, wherein a plurality of photodiodes are spaced apart within the substrate; A first oxide region and a second oxide region are alternately disposed in the substrate between adjacent photodiodes. The first oxide region and the second oxide region have different shapes and are asymmetrical about the photodiode. A deep trench isolation structure is disposed within the first oxidation zone and the second oxidation zone; A grid structure is disposed on the substrate between the photodiodes; as well as A filter structure is disposed on the photodiode.

2. The image sensor according to claim 1, characterized in that, The interfaces between the first oxide region and the second oxide region and the substrate are multiple irregular continuous arcs, and the shapes of the arcs at the interfaces between the first oxide region and the second oxide region and the substrate are different.

3. The image sensor according to claim 1, characterized in that, The first and second oxide regions are made of silicon oxide, and the deep trench isolation structure is made of a high dielectric constant material.

4. The image sensor according to claim 1, characterized in that, The first oxidation zone and the second oxidation zone have the same depth, and the depth of the deep trench isolation structure is 70% to 90% of the depth of the first oxidation zone.

5. The image sensor according to claim 1, characterized in that, The image sensor also includes an optical control system that extends from the surface of the photodiode into the photodiode, and the interface between the optical control system and the photodiode is arc-shaped.

6. A method for manufacturing an image sensor, characterized in that, include: A substrate is provided in which a plurality of photodiodes are disposed at intervals. A first oxide region and a second oxide region are alternately formed in the substrate between adjacent photodiodes. The first oxide region and the second oxide region have different shapes and are asymmetrical about the photodiode. Deep trench isolation structures are formed in the first oxidation zone and the second oxidation zone; A grid structure is formed on the substrate between the photodiodes; as well as A filter structure is formed on the photodiode.

7. The method for manufacturing an image sensor according to claim 6, characterized in that, The methods for fabricating the first oxidation region and the second oxidation region include: A first photoresist layer is formed on the substrate, and a plurality of first openings are formed on the first photoresist layer, the first openings being spaced apart to expose the substrate between the photodiodes; Using the first photoresist layer as a mask, the substrate exposed by the first opening is subjected to a first ion implantation process to form a first doped region; Remove the first photoresist layer and form a second photoresist layer on the substrate. A plurality of second openings are formed on the second photoresist layer, and the second openings and the first openings are alternately exposed to expose the substrate between the photodiodes. Using the second photoresist layer as a mask, a second ion implantation process is performed on the substrate exposed by the second opening to form a second doped region; The second photoresist layer is removed, and the substrate is subjected to heat treatment. The dopant ions in the first doped region and the second doped region react with the silicon in the substrate to form a first oxide region and a second oxide region.

8. The method for manufacturing an image sensor according to claim 7, characterized in that, The first ion implantation process includes at least two tilt implantations on each side of the substrate, with the two tilt implantation angles being unequal; the implanted ions are oxygen ions.

9. The method for manufacturing an image sensor according to claim 8, characterized in that, The second ion implantation process includes at least two tilt implantations on each side of the substrate, with the two tilt implantation angles being unequal. And / or, when performing the first ion implantation process and the second ion implantation process, at least one of the following parameters is different: the number of tilt implantations, the implantation angle, or the implantation dose.

10. The method for manufacturing an image sensor according to claim 6, characterized in that, The manufacturing method further includes: Before forming the first oxide region and the second oxide region, a patterned photoresist layer is formed on the substrate, and a plurality of grooves are formed on the patterned photoresist layer. The grooves expose a portion of the photodiode, and the opening size of the grooves increases from the surface of the substrate. Using the patterned photoresist layer as a mask, the portion of the photodiode exposed by the groove is etched to form a recess; A first dielectric layer and a second dielectric layer are sequentially deposited in the substrate and the recess; The first dielectric layer and the second dielectric layer are planarized to form an optical control system within the recess.

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