An image sensor

Abstract

The utility model discloses an image sensor, belonging to the field of semiconductor technology. The image sensor at least includes: a substrate, including a first surface and a second surface arranged oppositely; a deep trench isolation structure extending from the first surface to the inside of the substrate; a bonding layer arranged on the deep trench isolation structure; and a composite grid structure arranged on the bonding layer, the composite grid structure including a first material layer, a second material layer and a side wall, the second material layer is arranged on the first material layer, and the side wall is arranged around the first material layer and the second material layer. The image sensor provided by the utility model can improve the optical crosstalk problem of the back-illuminated image sensor, and improve the light conversion efficiency and yield of the image sensor.

Description

Technical Field

[0001] The utility model belongs to the technical field of semiconductors, and particularly relates to an image sensor. Background Art

[0002] Image sensors are devices that convert optical signals into electrical signals. They are widely used in photography, security systems, smart phones, fax machines, scanners, and medical electronics. Among them, back-side illumination (BSI) image sensors have the advantages of higher sensitivity, better wiring layout, and high-speed recording. They are used in fields that require high pixel performance of image sensors. In back-illuminated image sensors, the composite metal grid (CMG) process can effectively isolate adjacent filters, but conventional composite metal grids currently have problems such as optical crosstalk, low light conversion efficiency, and increased tensile stress on the wafer, resulting in serious yield loss. Utility Model Content

[0003] The purpose of the utility model is to provide an image sensor. The image sensor provided by the utility model can improve the optical crosstalk problem of a back-illuminated image sensor, improve the light conversion efficiency of the image sensor, and improve the yield of the image sensor.

[0004] In order to solve the above technical problems, the utility model provides an image sensor, comprising:

[0005] A substrate comprising a first surface and a second surface disposed opposite to each other;

[0006] a deep trench isolation structure extending from the first surface into the substrate;

[0007] an adhesive layer, disposed on the deep trench isolation structure; and

[0008] A composite grid structure is arranged on the bonding layer, and the composite grid structure includes a first material layer, a second material layer and a side wall. The second material layer is arranged on the first material layer, and the side wall is arranged around the first material layer and the second material layer.

[0009] In an embodiment of the present invention, the width of the bonding layer is less than or equal to the width of the deep trench isolation structure.

[0010] In an embodiment of the present invention, when the width of the bonding layer is smaller than the width of the deep trench isolation structure, the width difference between the bonding layer and the deep trench isolation structure is 10 nm to 30 nm.

[0011] In an embodiment of the present invention, the sum of the maximum widths of the first material layer and the side walls on both sides is equal to the width of the bonding layer.

[0012] In an embodiment of the present invention, the ratio of the width of the first material layer to the maximum width of the side wall on one side is 4:1 to 6:1.

[0013] In an embodiment of the present invention, the maximum width of the sidewall spacer on one side is 10 nm to 18 nm.

[0014] In an embodiment of the present invention, the widths of the first material layer and the second material layer are equal, and the thickness ratio of the first material layer to the second material layer is 0.8:1 to 1.2:1.

[0015] In an embodiment of the present invention, the image sensor further comprises a protection layer, and the protection layer is arranged on the substrate and the top and side walls of the composite grid structure.

[0016] In an embodiment of the present invention, the sum of the width of the adhesive layer and the thickness of the protection layers on both sides is greater than the width of the deep trench isolation structure.

[0017] In an embodiment of the present invention, the sidewall is a light shielding layer, and the light shielding layer includes a metal tungsten layer.

[0018] In summary, the utility model provides an image sensor. The unexpected technical effect of the present application is that it can effectively isolate adjacent filters, optically isolate adjacent pixel units, improve the light blocking performance of the side wall, and thus improve the optical crosstalk problem of the back-illuminated image sensor, and at the same time improve the light conversion efficiency of the image sensor. It can ensure that the composite grid structure has the function of a conventional composite metal grid, while also improving the optical crosstalk problem of the back-illuminated image sensor, while avoiding various problems caused by excessive tensile stress of the side wall on the substrate, thereby improving the yield of the image sensor. It can avoid contact between the side wall and the air, reduce oxidation, and ensure the light blocking performance of the side wall. It can relieve the stress between the second dielectric layer and the substrate, reduce the generation of dark current, thereby reducing the number of white pixels of the image sensor and improving the quality of the image sensor. At the same time, the second dielectric layer can also serve as a back anti-reflection layer to improve the light conversion efficiency. It improves the isolation strength between the photodiodes, avoids the interference of parasitic light pollution, and improves the isolation effect of the deep trench isolation structure.

[0019] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 Schematic diagram of a deep trench isolation structure in an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of a composite grid structure in one embodiment of the utility model.

[0023] Figure 3 FIG. 1 is a schematic diagram of an image sensor in an embodiment of the present invention.

[0024] Description of labels:

[0025] 100, substrate; 101, first surface; 102, second surface; 110, first dielectric layer; 120, second dielectric layer; 130, insulating medium; 140, air gap; 150, deep trench isolation structure; 160, bonding layer; 171, first material layer; 172, second material layer; 180, side wall; 190, protective layer; 201, filter; 202, microlens; 200, structural layer. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0028] In the present invention, it should be noted that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first" and "second" appear, they are only used for description and distinction purposes, and cannot be understood as indicating or implying relative importance.

[0029] CMOS image sensor is a typical solid-state imaging sensor, which usually includes semiconductor devices such as pixel unit array, row driver, column driver, timing control logic, AD converter, data bus output interface and control interface. Multiple semiconductor devices are usually integrated on the same silicon wafer, and multiple semiconductor devices are isolated from each other. CMOS image sensor has the advantages of small size, low power consumption, low price and mass production, and occupies a large share in the field of image sensors. The utility model provides an image sensor, which adopts a composite grid structure, which can improve the light absorption performance and anti-optical crosstalk ability of the composite grid structure, reduce stress problems, and improve the performance of the CMOS image sensor. The composite grid structure provided by the utility model can be applied to back-illuminated CMOS image sensors with different structures.

[0030] See also Figure 1 As shown, in one embodiment of the utility model, the image sensor includes a substrate 100, wherein the substrate 100 can be any applicable semiconductor material, specifically, for example, a substrate such as silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), silicon germanium (GeSi), sapphire or silicon wafer, and also includes a stacked structure composed of these semiconductors, or silicon on insulator, stacked silicon on insulator, stacked silicon germanium on insulator, silicon germanium on insulator, and germanium on insulator, etc., which can be selected according to the preparation requirements of the semiconductor structure. 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 homogeneous epitaxial layer. In other embodiments, the substrate 100 can be selected from other semiconductor materials, and at the same time, a doped or undoped semiconductor substrate can be selected.

[0031] See also Figure 1As shown, in one embodiment of the utility model, the substrate 100 includes a first surface 101 and a second surface 102 arranged opposite to each other, and on the second surface 102, a plurality of semiconductor devices (not shown in the figure) are arranged on the substrate 100. Among them, the semiconductor devices include, for example, pixel units, row drivers, column drivers, timing control logic, AD converters, data bus output interfaces and control interfaces, etc. Among them, a photodiode is arranged in each pixel unit to form a pixel point, and a plurality of pixel units form a two-dimensional pixel array. During the operation of the CMOS image sensor, the object is focused on the pixel array through the imaging lens, each photodiode converts the light intensity into an electrical signal, and the control circuit electrically connected to the photodiode selects the pixel to be operated, and reads the electrical signal on the pixel. Then, the electrical signal is amplified and subjected to denoising and other processing, and then output. The row driver, column driver, timing control logic, AD converter, data bus output interface and control interface, etc. on the substrate 100 are used to control reset, integration and readout, etc. After the semiconductor device is fabricated on the substrate 100, a multi-layer metal wiring layer is arranged on the semiconductor device, the semiconductor device is connected, and then bonded with the carrier to form a structure layer 200, that is, the structure layer 200 includes a plurality of semiconductor devices, a multi-layer metal wiring layer, and a carrier, etc. The carrier is, for example, one of a rigid packaging substrate, a flexible packaging substrate, and a ceramic packaging substrate, etc., and is specifically selected according to the requirements of the image sensor.

[0032] See also Figure 1 As shown, in one embodiment of the utility model, the image sensor includes a deep trench isolation structure 150, the deep trench isolation structure 150 extends from the first surface 101 of the substrate 100 to the inside of the substrate 100, and the bottom of the deep trench isolation structure 150 has a preset distance from the second surface 102. The area between adjacent deep trench isolation structures 150 is a photoelectric sensing area to form a photodiode for converting an optical signal into an electrical signal. The deep trench isolation structure 150 includes a first dielectric layer 110 and a second dielectric layer 120, and the second dielectric layer 120 includes a first high dielectric layer and a second high dielectric layer. To make the picture clear, the first high dielectric layer and the second high dielectric layer are not shown in the figure. Among them, the first dielectric layer 110 is arranged on the sidewall and bottom of the deep trench and the substrate 100, and completely covers the sidewall and bottom of the deep trench and the substrate 100, the first high dielectric layer is arranged on the first dielectric layer 110, and the second high dielectric layer is arranged on the first high dielectric layer.

[0033] See also Figure 1 As shown, in one embodiment of the present invention, the first dielectric layer 110 is, for example, a silicon oxide layer, and the thickness of the first dielectric layer 110 is, for example, Another example is The thickness of the first dielectric layer 110 on the substrate 100 is greater than the thickness of the first dielectric layer 110 on the sidewall and bottom of the deep trench. The first high dielectric layer and the second high dielectric layer can use dielectric materials with the same dielectric constant, or of course, dielectric materials with different dielectric constants. In this embodiment, the first high dielectric layer and the second high dielectric layer use dielectric materials with different dielectric constants, and the first high dielectric layer is, for example, an aluminum oxide layer, and the second high dielectric layer is, for example, a tantalum oxide layer. The thickness of the first high dielectric layer is, for example, Another example is or etc., the thickness of the second high dielectric layer is, for example, Another example is or Etc. In other embodiments, the high dielectric layer may select other structures according to the manufacturing requirements. By forming a second dielectric layer 120 with a high dielectric constant, the dark current of the image sensor can be further reduced. By arranging the first dielectric layer between the second dielectric layer and the substrate, the first dielectric layer acts as a buffer layer, which can relieve the stress between the second dielectric layer and the substrate. At the same time, during the operation of the CMOS image sensor, the substrate is positively charged, the second dielectric layer is negatively charged, and the first dielectric layer acts as a capacitor dielectric layer between the substrate and the second dielectric layer. The first dielectric layer has high coverage and can reduce the generation of dark current, thereby reducing the number of white pixels of the CMOS image sensor and improving the quality of the CMOS image sensor. At the same time, the second dielectric layer can also serve as a back anti-reflection layer to improve the light conversion efficiency.

[0034] See also Figure 1 As shown, in one embodiment of the utility model, an insulating medium 130 is provided on the second dielectric layer 120, and the insulating medium 130 fills the deep groove and covers the surface of the second dielectric layer 120. In this embodiment, the insulating medium 130 is, for example, insulating silicon oxide. In other embodiments, the insulating medium 130 may also be an insulating material such as borosilicate glass. Among them, the insulating medium 130 is obtained, for example, by plasma enhanced atomic layer deposition (PEALD), high density plasma chemical vapor deposition (HDP-CVD) or high aspect ratio chemical vapor deposition (HARP-CVD). After the insulating medium 130 is deposited, an annealing process may be performed to increase the density and stress of the insulating medium 130. In one embodiment of the utility model, the thickness of the insulating medium 130 on the substrate 100 is, for example,

[0035] See also Figure 1As shown, in one embodiment of the utility model, during the deposition process of the insulating medium 130, an air gap 140 is formed in the insulating medium 130, and the top of the air gap 140 is, for example, flush with the surface of the second dielectric layer 120, or lower than the surface of the second dielectric layer 120. The first dielectric layer 110, the second dielectric layer 120, the insulating medium 130 and the air gap 140 in the deep trench constitute a deep trench isolation structure 150. The air gap 140 improves the isolation strength between the photoelectric sensing regions, avoids the interference of parasitic light pollution, and improves the isolation effect of the formed deep trench isolation structure.

[0036] See also Figure 1 to Figure 2 As shown, in one embodiment of the present invention, a bonding layer 160 is disposed on the deep trench isolation structure 150. The bonding layer 160 is, for example, titanium, titanium nitride, or a stack of titanium and titanium nitride, and the thickness of the bonding layer 160 is, for example, In one embodiment of the present invention, the width of the bonding layer 160 is, for example, equal to the width of the deep trench isolation structure 150. In another embodiment of the present invention, the width of the bonding layer 160 is, for example, less than the width of the deep trench isolation structure 150, and the width difference between the bonding layer 160 and the deep trench isolation structure 150 is, for example, 10nm to 30nm. By providing the bonding layer 160, the adhesion between the composite grid structure and the substrate is improved, and at the same time, the metal in the composite grid structure is prevented from penetrating into the deep trench isolation structure 150. At the same time, when the first material layer 171 and the second material layer 172 are subsequently formed, the bonding layer 160 can also serve as a hard mask layer for the substrate and the deep trench isolation structure.

[0037] See also Figure 1 to Figure 2 As shown, in one embodiment of the utility model, a composite grid structure is arranged on the bonding layer 160, and the composite grid structure includes a first material layer 171, a second material layer 172 and a side wall 180. The first material layer 171 is arranged on the bonding layer 160, the second material layer 172 is arranged on the first material layer 171, and the side wall 180 is arranged around the first material layer 171 and the second material layer 172. Among them, the first material layer 171 is, for example, a metal material layer, and for example, includes an aluminum layer, a copper layer or an aluminum-copper layer, etc., to effectively isolate adjacent filters and serve as optical isolation between adjacent pixel units. The second material layer 172 is, for example, a silicon oxide layer, which is used for a hard mask layer. The side wall 180 is, for example, a light shielding layer, and the light shielding layer includes, for example, a metal tungsten layer. The reflectivity of the side wall 180 is less than the reflectivity of the first material layer 171, and the light shielding performance of the side wall 180 is better, thereby improving the optical crosstalk problem of the back-illuminated image sensor, and at the same time, the light conversion efficiency of the image sensor can be improved.

[0038] See also Figure 1 to Figure 2As shown, in one embodiment of the present invention, the sidewall 180 is, for example, an arc or a rectangle, and the height of the sidewall 180 is flush with the surface of the second material layer 172. The sum of the maximum widths of the first material layer 171 and the sidewalls 180 on both sides is equal to the width of the bonding layer 160, and the ratio of the width of the first material layer 171 to the maximum width of the sidewall 180 on one side is, for example, 4:1, etc. In one embodiment of the present invention, the maximum width of the sidewall 180 on one side is, for example, 10nm to 18nm. The thickness ratio of the first material layer 171 to the second material layer 172 is, for example, 0.8:1 to 1.2:1, and for example, 1:1, etc. The widths of the first material layer 171 and the second material layer 172 are equal. By controlling the thickness of the side wall 180, it is possible to ensure that the composite grid structure has the function of a conventional composite metal grid. At the same time, the composite grid structure provided by the present application can also improve the optical crosstalk problem of the back-illuminated image sensor, while avoiding various problems caused by excessive tensile stress of the side wall 180 on the substrate 100, such as defocusing during lithography operations, thereby improving the yield of the image sensor.

[0039] See also Figures 2 to 3 As shown, in one embodiment of the present invention, a protective layer 190 is provided on the insulating medium 130 on the substrate 100 and on the top and sidewalls of the composite grid structure. The protective layer 190 is, for example, a silicon oxide layer. In one embodiment of the present invention, the protective layer 190 on the sidewall of the composite grid structure is provided vertically to the substrate 100, and the thickness of the protective layer 190 is, for example, 8nm to 15nm. The sum of the width of the bonding layer 160 and the thickness of the protective layers 190 on both sides is greater than the width of the deep trench isolation structure 150. By providing the protective layer 190, the sidewall 180 can be prevented from contacting with the air, oxidation can be reduced, and the light blocking performance of the sidewall can be ensured.

[0040] See also Figures 2 to 3As shown, in one embodiment of the utility model, a filter structure is provided on the protective layer 190 on the substrate 100, that is, the filter structure is provided on the photoelectric sensing area. Among them, the filter structure includes a filter 201 and a microlens 202, the filter 201 is provided on the protective layer 190, and the microlens 202 is provided on the filter 201. In one embodiment of the utility model, the filter structure, for example, includes a plurality of color filters, and the plurality of color filters constitute a color filter array. Each color filter corresponds to a photoelectric sensing area. In this embodiment, the filter structure includes at least three primary color color filters, for example, a blue filter, a green filter and a red filter, and can be arranged in any suitable combination. For example, the blue filter, the green filter and the red filter can be arranged in an alternating manner. A transparent filter can also be provided, and the blue filter, the green filter, the red filter and a transparent filter are arranged in an alternating manner. The color filter can be a polymer material, such as a negative photoresist based on acrylic polymer, and can contain color dyes. When light passes through the color filter, it can change color and maintain a high transmittance of a certain band (color), thereby enhancing the efficiency of photoelectric conversion.

[0041] See also Figures 2 to 3 As shown, in one embodiment of the present invention, the top of the microlens 202 is in an arc shape that bulges outward, and can focus the incident light on the photoelectric sensing area. The curvature of the surface of the microlens 202 can be changed according to the focusing requirements to improve the photosensitivity efficiency. Among them, the number of photoelectric sensing areas and filter structures can be set according to actual needs, and the figure of this embodiment is only used as an example.

[0042] In summary, the utility model provides an image sensor. By improving the structure of the image sensor, the unexpected technical effect of the present application is that it can effectively isolate adjacent filters, optically isolate adjacent pixel units, improve the light-blocking performance of the side wall, and thus improve the optical crosstalk problem of the back-illuminated image sensor, and at the same time improve the light conversion efficiency of the image sensor. It can ensure that the composite grid structure has the function of a conventional composite metal grid, while also improving the optical crosstalk problem of the back-illuminated image sensor, while avoiding various problems caused by excessive tensile stress of the side wall on the substrate, and improving the yield of the image sensor. It can avoid contact between the side wall and the air, reduce oxidation, and ensure the light-blocking performance of the side wall. It can relieve the stress between the second dielectric layer and the substrate, reduce the generation of dark current, thereby reducing the number of white pixels of the image sensor and improving the quality of the image sensor. At the same time, the second dielectric layer can also serve as a back anti-reflection layer to improve the light conversion efficiency. The isolation strength between the photodiodes is improved, the interference of parasitic light pollution is avoided, and the isolation effect of the formed deep trench isolation structure is improved.

[0043] The embodiments of the utility model disclosed above are only used to help illustrate the utility model. The embodiments do not describe all the details in detail, nor do they limit the utility model to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the utility model, so that technicians in the relevant technical field can well understand and use the utility model. The utility model is limited only by the claims and their full scope and equivalents.

Claims

1. An image sensor, characterized in that: include: A substrate comprising a first surface and a second surface disposed opposite to each other; a deep trench isolation structure extending from the first surface into the substrate; An adhesive layer, disposed on the deep trench isolation structure; as well as A composite grid structure is arranged on the bonding layer, and the composite grid structure includes a first material layer, a second material layer and a side wall. The second material layer is arranged on the first material layer, and the side wall is arranged around the first material layer and the second material layer.

2. The image sensor according to claim 1, characterized in that The width of the bonding layer is less than or equal to the width of the deep trench isolation structure.

3. The image sensor according to claim 2, characterized in that When the width of the bonding layer is smaller than the width of the deep trench isolation structure, the width difference between the bonding layer and the deep trench isolation structure is 10 nm to 30 nm.

4. The image sensor according to claim 1, characterized in that The sum of the maximum widths of the first material layer and the side walls on both sides is equal to the width of the bonding layer.

5. The image sensor according to claim 4, characterized in that: The ratio of the width of the first material layer to the maximum width of the sidewall on one side is 4:1 to 6:

1.

6. The image sensor according to claim 4, characterized in that: The maximum width of the sidewall on one side is 10 nm to 18 nm.

7. The image sensor according to claim 1, characterized in that: The widths of the first material layer and the second material layer are equal, and the thickness ratio of the first material layer to the second material layer is 0.8:1 to 1.2:

1.

8. The image sensor according to claim 1, characterized in that The image sensor further includes a protection layer disposed on the substrate and a top and sidewalls of the composite grid structure.

9. The image sensor according to claim 8, characterized in that: The sum of the width of the bonding layer and the thickness of the protection layers on both sides is greater than the width of the deep trench isolation structure.

10. The image sensor according to claim 1, wherein: The sidewall is a light shielding layer, and the light shielding layer includes a metal tungsten layer.

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