Image sensor and manufacturing method thereof

Abstract

The embodiment of the invention provides an image sensor and a manufacturing method thereof. The image sensor includes: a substrate including a photodiode layer and a circuit layer that are stacked; the light-transmitting layer is located on the surface of the substrate; the light transmitting layer comprises a first dielectric layer and a second dielectric layer; wherein the first dielectric layer is provided with a first surface and a second surface which are oppositely arranged along the lamination direction, the first surface is a plane close to the substrate, and the second surface is a curved surface far away from the substrate; the second dielectric layer covers the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface and is used for receiving optical signals.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of semiconductor technology, and more particularly to an image sensor and a method for manufacturing the same. Background Art

[0002] Image sensors are usually manufactured based on complementary metal oxide semiconductor (CMOS) technology. According to the different positions of receiving light, image sensors can be divided into front side illumination (FSI) image sensors and back side illumination (BSI) image sensors. Among them, back side illumination image sensors currently have great advantages, which can capture a larger amount of incoming light and achieve high-quality images.

[0003] However, in practical applications, image sensors still have many problems that need to be improved. Summary of the invention

[0004] In view of this, an embodiment of the present disclosure provides an image sensor and a method for manufacturing the same.

[0005] To achieve the above objectives, the technical solution of the present disclosure is implemented as follows:

[0006] In a first aspect, an embodiment of the present disclosure provides an image sensor, the image sensor comprising:

[0007] A substrate, the substrate comprising a stacked photodiode layer and a circuit layer;

[0008] A light-transmitting layer, the light-transmitting layer is located on the surface of the substrate; the light-transmitting layer includes a first dielectric layer and a second dielectric layer; wherein the first dielectric layer has a first surface and a second surface arranged opposite to each other along a stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate; the second dielectric layer covers the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving optical signals.

[0009] In some embodiments, the light-transmitting layer includes a plurality of protruding structures protruding in a direction away from the substrate; or, the light-transmitting layer includes a plurality of concave structures concave in a direction away from the substrate.

[0010] In some embodiments, the second surface of the first dielectric layer includes a plurality of curved surfaces protruding in a direction away from the substrate, and the thickness of the second dielectric layer is uniform at all locations; the first dielectric layer and the second dielectric layer together constitute a plurality of the protruding structures.

[0011] In some embodiments, the second surface of the first dielectric layer includes a plurality of curved surfaces recessed toward the substrate, and the second dielectric layer has a uniform thickness at all locations; the first dielectric layer and the second dielectric layer together constitute a plurality of recessed structures.

[0012] In some embodiments, the image sensor further comprises:

[0013] A third dielectric layer, the third dielectric layer covers the second dielectric layer; and a surface of the third dielectric layer is a plane.

[0014] In some embodiments, the photodiode layer includes a plurality of photodiodes arranged in an array; and the image sensor further includes:

[0015] A grid structure is located on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each of the photodiodes in the photodiode layer in the stacking direction.

[0016] In some embodiments, in the stacking direction, each of the photodiodes is aligned with one of the protruding structures or one of the recessed structures; or, each of the photodiodes is aligned with a plurality of the protruding structures or a plurality of the recessed structures.

[0017] In some embodiments, the refractive index of the material of the first dielectric layer is different from the refractive index of the material of the second dielectric layer.

[0018] In some embodiments, the material of the first dielectric layer includes a photoresist material and an organic material, and the material of the second dielectric layer includes a high dielectric constant material.

[0019] In a second aspect, an embodiment of the present disclosure provides a method for manufacturing an image sensor, the method for manufacturing an image sensor comprising:

[0020] Providing a substrate; the substrate comprising a stacked photodiode layer and a circuit layer; the photodiode layer comprising a plurality of photodiodes arranged in an array;

[0021] A first dielectric layer is formed on the surface of the substrate; the first dielectric layer has a first surface and a second surface which are arranged opposite to each other along a stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate;

[0022] A second dielectric layer is formed on the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving optical signals.

[0023] In some embodiments, forming a first dielectric layer on the surface of the substrate includes:

[0024] forming a first dielectric material layer on the surface of the substrate;

[0025] The first dielectric material layer is photolithographically processed using a photomask to form the first dielectric layer; wherein the photomask has different light transmittances in different regions along its thickness direction.

[0026] In some embodiments, forming a first dielectric layer on the surface of the substrate includes:

[0027] inkjet printing the first dielectric material to form a first dielectric material layer on the surface of the substrate;

[0028] The first dielectric material layer is cured to form the first dielectric layer.

[0029] In some embodiments, the manufacturing method further comprises:

[0030] forming a third dielectric layer on a surface of the second dielectric layer;

[0031] performing a planarization process on the surface of the third dielectric layer;

[0032] A grid structure is formed on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each of the photodiodes in the photodiode layer in the stacking direction.

[0033] In some embodiments, the material of the first dielectric layer includes a photoresist material and an organic material, and the material of the second dielectric layer includes a high dielectric constant material.

[0034] In some embodiments, the refractive index of the material of the first dielectric layer is different from the refractive index of the material of the second dielectric layer.

[0035] The disclosed embodiment provides an image sensor, which includes: a substrate, the substrate includes a stacked photodiode layer and a circuit layer; a light-transmitting layer, the light-transmitting layer is located on the surface of the substrate; the light-transmitting layer includes a first dielectric layer and a second dielectric layer; wherein the first dielectric layer has a first surface and a second surface arranged opposite to each other along the stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate; the second dielectric layer covers the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving light signals. In the disclosed embodiment, the first surface of the first dielectric layer is a plane, and the second surface of the first dielectric layer is a curved surface. In this way, the first dielectric layer forms a microlens structure in the light-transmitting layer for converging light. The microlens structure can capture a larger amount of incoming light, thereby improving the imaging quality of the image sensor in a dark light environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the structure of an image sensor provided as an example;

[0037] Figure 2 A schematic diagram of the structure of an image sensor provided by an embodiment of the present disclosure;

[0038] Figure 3 A schematic diagram of the structure of another image sensor provided by an embodiment of the present disclosure;

[0039] Figure 4 A flowchart of a method for manufacturing an image sensor provided by an embodiment of the present disclosure;

[0040] FIG. 5A to FIG. 5D A step diagram of a method for manufacturing an image sensor provided by an embodiment of the present disclosure;

[0041] FIG. 6A to FIG. 6B A schematic diagram of the structure of the photomask provided in an embodiment of the present disclosure in the XY plane. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present disclosure and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0043] In the following description, a large number of specific details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0044] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0045] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present disclosure necessarily has the first element, component, region, layer or part.

[0046] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0047] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0048] In order to thoroughly understand the present disclosure, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present disclosure. The preferred embodiments of the present disclosure are described in detail below, but in addition to these detailed descriptions, the present disclosure may also have other implementations.

[0049] An image sensor is a sensor that can convert the color and brightness of light captured by the lens into electrical signals and transmit them to the processor. Image sensors can be divided into FSI image sensors and BSI image sensors. Among them, BSI image sensors currently have great advantages. They can capture a larger amount of incoming light and achieve high-quality images. The first step of both FSI and BSI technology is to converge the light signal from outside the image sensor and make it enter the optical area of ​​the photodiode. After receiving the light signal, the photodiode can convert it into an electrical signal, which can be further converted into a graphic signal by the image sensor. However, since the size of the current image sensor is limited by the size of the internal space of the electronic product, the size of a single pixel is also limited, making its imaging quality unsatisfactory under extreme dark light conditions.

[0050] Figure 1 The schematic diagram of the structure of an image sensor provided as an example. Figure 1 As shown, the image sensor 100 includes a stacked photodiode layer 101, a circuit layer 102, a light-transmitting layer 103, a dielectric layer 104 and a grid structure 105. Among them, the photodiode layer 101 includes a plurality of photodiodes arranged in an array. The light signal from the outside of the image sensor 100 can reach the photodiode layer 101 through the grid structure 105, the dielectric layer 104, the light-transmitting layer 103 and the circuit layer 102, and enter from the front of the photodiode. Afterwards, the light signal entering the photodiode will be converted into an electrical signal. The circuit layer 102 includes a multi-layer interconnection structure, which can be electrically connected to a plurality of photodiodes, thereby transmitting the electrical signal output by the photodiode to the circuit layer 102. The light-transmitting layer 103 can be used as a voltage adjustment layer and a reflective layer to improve the optical performance of the image sensor. The thickness of the light-transmitting layer 103 is consistent everywhere. The dielectric layer 104 can be used as an insulating layer to achieve insulation between the light-transmitting layer 103 and the grid structure 105. The grid structure 105 has a plurality of defined cavities 106 aligned one by one with each photodiode in the photodiode layer 101 in the stacking direction. The optical signal can be irradiated to the photodiode through the defined cavities 106 of the grid structure 105, thereby reducing crosstalk.

[0051] It should be noted that Figure 1In the figure, only the image sensor 100 is taken as a front-illuminated image sensor as an example for explanation. In other examples, the image sensor can also be a back-illuminated image sensor. Specifically, the back-illuminated image sensor includes a stacked circuit layer, a photodiode layer, a light-transmitting layer, a dielectric layer and a grid structure. Among them, the photodiode layer is located on the circuit layer, so that the direction of the incident light path of the element of the photodiode layer is reversed, so that the light signal enters the photodiode from the back. Here, the light-transmitting layer, the dielectric layer and the grid structure can refer to Figure 1 , I will not go into details here.

[0052] However, in the above examples, no matter the front-illuminated image sensor or the back-illuminated image sensor, the imaging quality in a dark environment is not ideal.

[0053] In view of this, an embodiment of the present disclosure provides an image sensor and a method for manufacturing the same.

[0054] Before introducing the image sensor and the manufacturing method thereof provided by the embodiment of the present disclosure, various directions that may be involved in the embodiment of the present disclosure are first defined. The stacking direction is defined as the Z direction, and the X direction and the Y direction are defined in a plane perpendicular to the Z direction, and the X direction and the Y direction may intersect. In a specific embodiment, the X direction and the Y direction may be perpendicular to each other, so that the X direction, the Y direction and the Z direction are perpendicular to each other.

[0055] Figure 2 FIG. 1 is a schematic diagram of the structure of an image sensor provided by an embodiment of the present disclosure. Figure 2 As shown, an embodiment of the present disclosure provides an image sensor 200, which includes: a substrate 201, the substrate 201 includes a stacked photodiode layer 202 and a circuit layer 203; a light-transmitting layer 204, the light-transmitting layer 204 is located on the surface of the substrate 201; the light-transmitting layer 204 includes a first dielectric layer 205 and a second dielectric layer 206; wherein the first dielectric layer 205 has a first surface 205a and a second surface 205b that are arranged opposite to each other along a stacking direction, the first surface 205a is a plane close to the substrate 201, and the second surface 205b is a curved surface away from the substrate 201; the second dielectric layer 206 covers the second surface 205b of the first dielectric layer 205; the surface of the second dielectric layer 206 is a curved surface for receiving optical signals.

[0056] It should be noted that, in the embodiment of the present disclosure, the substrate 201 includes a first semiconductor layer 207, and the first semiconductor layer 207 has a front surface 207a and a rear surface 207b that are relatively arranged along the stacking direction (i.e., the Z direction). The photodiode layer 202 is formed in the first semiconductor layer 207. Specifically, the photodiode layer 202 is formed on the front surface 207a of the first semiconductor layer 207, and the photodiode layer 202 includes a plurality of photodiodes arranged in an array along the X direction and the Y direction. In other words, a plurality of photodiodes arranged in an array are formed on the front surface 207a of the first semiconductor layer 207. Here, the photodiode as a photoelectric conversion element in the image sensor 200 can be used to convert the received light signal into an electrical signal, and one photodiode can correspond to one pixel in the image sensor 200.

[0057] In some embodiments, the material of the first semiconductor layer 207 may include a single substance, such as silicon, germanium, and carbon. Alternatively, the material of the first semiconductor layer 207 may include a compound semiconductor material, such as silicon carbide, gallium arsenide, indium arsenide, and indium phosphide. In other embodiments, the material of the first semiconductor layer 207 may also include silicon on an insulator. In still other embodiments, the material of the first semiconductor layer 207 may include an alloy semiconductor material, such as silicon germanium, silicon germanium carbide, gallium arsenic phosphide, and gallium indium phosphide.

[0058] The circuit layer 203 is located on the first semiconductor layer 207 and is in contact with the front surface 207a of the first semiconductor layer 207. In other words, the circuit layer 203 is located on the photodiode layer 202 and is in contact with the photodiode layer 202. The circuit layer 203 includes a dielectric layer 208 and a multilayer interconnection structure 209 located in the dielectric layer 208. The interconnection structure 209 can serve as a conductive structure to transmit the electrical signal converted by the photodiode to the circuit layer 203.

[0059] In the embodiment of the present disclosure, the interconnection structure 209 may include a vertical interconnection structure, such as a contact and a through hole. The interconnection structure 209 may also include a horizontal interconnection structure, such as a line structure extending in a horizontal direction (i.e., an X direction or a Y direction). The material of the interconnection structure 209 includes a conductive material, such as a metal. Exemplarily, the material of the interconnection structure 209 includes aluminum, copper, aluminum / silicon / copper alloy, titanium, titanium nitride, tungsten, polysilicon, metal silicide, or a metal combined therewith.

[0060] In the embodiment of the present disclosure, the preparation process of the interconnect structure 209 includes but is not limited to physical vapor deposition (PVD), chemical vapor deposition (CVD), photolithography and etching.

[0061] In the embodiment of the present disclosure, the dielectric layer 208 may have a multi-layer structure. The material of the dielectric layer 208 includes silicon dioxide, silicon nitride, silicon oxynitride, TEOS oxide, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), fluorosilicate glass (FSG), carbon-doped silicon oxide, xerogel, aerogel, fluorinated amorphous carbon, polyparaxylene, BCB (bis-benzocyclobutenes), polyimide or other suitable materials.

[0062] In the embodiment of the present disclosure, the preparation process of the dielectric layer 208 includes spin coating, physical vapor deposition, chemical vapor deposition or other suitable processing processes.

[0063] It should be noted that, in the process of manufacturing the image sensor 200, a substrate may be first provided, and a circuit layer 203 may be formed on the substrate. Afterwards, the circuit layer 203 formed on the substrate may be connected to the first semiconductor layer 207 by bonding, so that the surface of the circuit layer 203 is in contact with the front surface 207a of the first semiconductor layer 207. Thus, after the bonding is completed, the substrate is located on the side of the circuit layer 203 away from the first semiconductor layer 207. The substrate may be thinned in a subsequent process to form a second semiconductor layer 210, thereby reducing the loss of light signals reaching the photodiode. Figure 2 As shown, the second semiconductor layer 210 is located on the surface of the substrate 201 and can be a part of the substrate 201 .

[0064] In the embodiment of the present disclosure, the material of the second semiconductor layer 210 may be the same as the material of the first semiconductor layer 207 .

[0065] In the embodiment of the present disclosure, the light-transmitting layer 204 is located on the substrate 201 and contacts the surface of the substrate 201. The light-transmitting layer 204 includes a first dielectric layer 205 and a second dielectric layer 206. The first dielectric layer 205 has a first surface 205a and a second surface 205b that are arranged opposite to each other along the stacking direction (Z direction). The first surface 205a of the first dielectric layer 205 contacts the surface of the substrate 201, and the second surface 205b of the first dielectric layer 205 contacts the second dielectric layer 206.

[0066] In some embodiments, the material of the first dielectric layer 205 includes a photoresist material and an organic material, and the material of the second dielectric layer 206 includes a high dielectric constant material.

[0067] In the disclosed embodiment, the photoresist material includes SU-8 material. SU-8 material has become a promising material for manufacturing microlenses due to its high light transmittance, high refractive index and low polymer volume shrinkage in the visible light to near infrared range. In addition, SU-8 material also has good mechanical properties, thermal stability and optical properties, making it suitable for manufacturing micro-optical elements.

[0068] In the disclosed embodiments, the organic material includes acrylic material, epoxy resin material, polyimide material, etc. The organic material has the characteristics of high light transmittance and stable chemical properties.

[0069] In the disclosed embodiment, the high dielectric constant material includes hafnium dioxide, zirconium dioxide, titanium dioxide, etc. The second dielectric layer 206 made of the high dielectric constant material can be used as a voltage adjustment layer and a reflective layer to reduce the dark current generated by the surface damage of the second semiconductor layer 210 and enhance the light collection efficiency of the image sensor, thereby improving the optical performance of the image sensor 200.

[0070] In some embodiments, the light-transmitting layer includes a plurality of protruding structures protruding in a direction away from the substrate.

[0071] like Figure 2 As shown, in some embodiments, the second surface 205b of the first dielectric layer 205 includes a plurality of curved surfaces protruding in a direction away from the substrate 201, and the thickness of the second dielectric layer 206 is uniform everywhere; the first dielectric layer 205 and the second dielectric layer 206 together constitute a plurality of protruding structures 211.

[0072] Here, it should be noted that Figure 2 In the illustrated image sensor 200, the first surface 205a of the first dielectric layer 205 is a plane close to the substrate 201, and the second surface 205b of the first dielectric layer 205 includes a plurality of curved surfaces convex in a direction away from the substrate 201 (positive direction of the Z direction). In addition, in the embodiment of the present disclosure, the refractive index of the material of the first dielectric layer 205 is different from the refractive index of the material of the second dielectric layer 206. Specifically, the refractive index of the first dielectric layer 205 is greater than the refractive index of the second dielectric layer 206. In this way, the first dielectric layer 205 and the second dielectric layer 206 can form a plurality of convex structures 211 together, and each convex structure 211 includes a micro convex lens structure for converging light formed by the first dielectric layer 205. Here, the micro convex lens structure can converge the light that passes through the second dielectric layer 206 and reaches the first dielectric layer 205, so as to capture a larger amount of incoming light, thereby improving the imaging quality of the image sensor 200 in a dark light environment. Furthermore, at each protruding structure 211, the surface of the second dielectric layer 206 protrudes in a direction away from the substrate 201. Figure 1The light-transmitting layer 103 having a flat surface, Figure 2 The second dielectric layer 206 in the image sensor 200 has a larger light receiving surface. In other words, when the light passes through the grid structure and the third dielectric layer and reaches the surface of the second dielectric layer 206, there is a larger contact area between the second dielectric layer 206 and the light. In this way, the sensitivity of the second dielectric layer 206 to light is improved, so that the second dielectric layer 206 can receive more light signals, thereby improving the imaging quality of the image sensor 200.

[0073] In some other embodiments, the light-transmitting layer includes a plurality of concave structures that are concave in a direction away from the substrate.

[0074] Figure 3 FIG. 3 is a schematic diagram of the structure of another image sensor 300 provided in an embodiment of the present disclosure. Figure 3 As shown, the image sensor 300 includes a substrate 301 and a light-transmitting layer 304. The substrate 301 includes a stacked photodiode layer 302 and a circuit layer 303. The light-transmitting layer 304 includes a first dielectric layer 305 and a second dielectric layer 306. The first dielectric layer 305 has a first surface 305a and a second surface 305b that are arranged opposite to each other along the stacking direction. The first surface 305a is a plane close to the substrate 301, and the second surface 305b is a curved surface away from the substrate 301. The second dielectric layer 306 covers the second surface 305b of the first dielectric layer 305. The surface of the second dielectric layer 306 is a curved surface for receiving optical signals. In some embodiments, the second surface 305b of the first dielectric layer 305 includes a plurality of curved surfaces that are recessed in the direction of the substrate 301, and the thickness of the second dielectric layer 306 is consistent at all locations; the first dielectric layer 305 and the second dielectric layer 306 together constitute a plurality of recessed structures 311.

[0075] Here, it should be noted that Figure 3In the illustrated image sensor 300, the first surface 305a of the first dielectric layer 305 is a plane close to the substrate 301, and the second surface 305b of the first dielectric layer 305 includes a plurality of curved surfaces that are concave in the direction of the substrate 301 (the opposite direction of the Z direction). In addition, in the embodiment of the present disclosure, the refractive index of the material of the first dielectric layer 305 is different from the refractive index of the material of the second dielectric layer 306. Specifically, the refractive index of the first dielectric layer 305 is less than the refractive index of the second dielectric layer 306. In this way, the first dielectric layer 305 and the second dielectric layer 306 can form a plurality of concave structures 311 together, and each concave structure 311 includes a micro concave lens structure formed by the first dielectric layer 305 for converging light. Here, the micro concave lens structure can converge the light that passes through the second dielectric layer 306 and reaches the first dielectric layer 305 to capture a larger amount of incoming light, thereby improving the imaging quality of the image sensor 300 in a dark light environment. Furthermore, at each recessed structure 311, the surface of the second dielectric layer 306 is recessed toward the substrate 301. Figure 1 The light-transmitting layer 103 having a flat surface, Figure 3 The second dielectric layer 306 in the image sensor 300 has a larger light receiving surface. In other words, when the light passes through the grid structure and the third dielectric layer and reaches the surface of the second dielectric layer 306, there is a larger contact area between the second dielectric layer 306 and the light. In this way, the sensitivity of the second dielectric layer 306 to light is improved, so that the second dielectric layer 306 can receive more light signals, thereby improving the imaging quality of the image sensor 300.

[0076] like Figure 2 As shown, in some embodiments, the image sensor 200 further includes: a third dielectric layer 212 , the third dielectric layer 212 covers the second dielectric layer 206 ; and the surface of the third dielectric layer 212 is a plane.

[0077] Here, it should be noted that after forming the second dielectric layer 206, a third dielectric material layer can be formed on the surface of the second dielectric layer 206 by a deposition process. At this time, the surface of the third dielectric material layer is a curved surface. Afterwards, the surface of the third dielectric material layer can be processed by a chemical mechanical polishing (CMP) process to obtain a third dielectric layer 212 with a flat surface.

[0078] In the embodiment of the present disclosure, the third dielectric layer 212 may be an insulating layer. Exemplarily, the material of the third dielectric layer 212 may include one or more of silicon oxide, silicon nitride, and silicon oxynitride.

[0079] In some embodiments, the image sensor further includes: a grid structure, the grid structure is located on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each photodiode in the photodiode layer in the stacking direction.

[0080] like Figure 2 As shown, the grid structure 213 is located on the surface of the third dielectric layer 212. The grid structure 213 has a plurality of defined cavities 214 arranged in an array along the X direction and the Y direction. Here, the process method for forming the grid structure 213 includes: depositing a layer of opaque grid material layer on the third dielectric layer 212 by a deposition process; removing part of the grid material layer by a patterning process to form the grid structure 213. It can be understood that a plurality of through holes arranged in an array along the X direction and the Y direction and penetrating the grid material layer along the Z direction can be formed in the grid material layer by a patterning process. Each through hole can be defined as a defined cavity 214. Here, since the material of the grid structure 213 is an opaque material, and the defined cavity 214 is a through hole along the Z direction, the optical signal reaching the grid structure 213 can only propagate to the third dielectric layer 212 through the plurality of defined cavities 214 of the grid structure 213. Furthermore, in the Z direction, the defined cavities 214 arranged in an array are aligned one by one with the photodiodes (PD) arranged in an array in the photodiode layer 202, and each defined cavity 214 exposes a portion of the upper surface of the third dielectric layer 212. In this way, the optical signal reaching the grid structure 213 can reach the photodiode aligned therewith through different defined cavities 214, so that the optical signals incident on each photodiode are isolated from each other, thereby reducing signal crosstalk.

[0081] In the embodiment of the present disclosure, the area of ​​the cross section of the cavity 214 along the XY direction may be greater than or equal to the area of ​​the projection of the photodiode along the Z direction on the substrate 201. The cross section of the cavity 214 along the XY direction may be rectangular, circular, or a shape corresponding to the projection shape of the photodiode along the Z direction on the substrate 201.

[0082] In the embodiment of the present disclosure, the material of the grid structure 213 may include a single metal, such as copper, nickel, zinc, tin, silver, gold, tungsten, magnesium, tantalum, titanium, molybdenum, platinum, aluminum, hafnium, ruthenium, etc. The material of the grid structure 213 may also include an alloy, such as a copper alloy or an aluminum alloy, etc.

[0083] In some embodiments, each photodiode is aligned with one protruding structure or one recessed structure in the stacking direction.

[0084] like Figure 2As shown, in the Z direction, each photodiode is aligned with a protruding structure 211. In this way, each protruding structure 211 can converge the light reaching the light-transmitting layer 204 to the photodiode aligned with it in the Z direction.

[0085] like Figure 3 As shown, in the Z direction, each photodiode is aligned with a recessed structure 311. Thus, each recessed structure 311 can converge the light reaching the light-transmitting layer 204 to the photodiode aligned with it in the Z direction.

[0086] In some other embodiments, in the stacking direction, each photodiode is aligned with a plurality of protruding structures or a plurality of recessed structures.

[0087] Here, it can be understood that when the light-transmitting layer has a convex structure or a concave structure, regardless of the number of the convex structures or the concave structures, the light-transmitting layer can achieve the convergence of incident light to capture a larger amount of incoming light. Therefore, in some embodiments, in the Z direction, each photodiode can be aligned with multiple convex structures or multiple concave structures. That is, multiple convex structures or multiple concave structures can converge the light reaching the light-transmitting layer 204 to a photodiode corresponding to it in the Z direction. In other embodiments, in the Z direction, multiple photodiodes can be aligned with a convex structure or a concave structure. That is, a convex structure or a concave structure can converge the light reaching the light-transmitting layer 204 to a plurality of photodiodes corresponding to it in the Z direction.

[0088] refer to Figure 2 In the embodiment of the present disclosure, the image sensor 200 may further include a filling layer ( Figure 2 The filling layer may cover the surface of the grid structure 213 and fill the defined cavity 214 of the grid structure 213. The surface of the filling layer may be a plane, and the material of the filling layer may be the same as that of the third dielectric layer 212.

[0089] In the embodiment of the present disclosure, the image sensor 200 may further include a filter layer ( Figure 2 ). The filter layer may include a plurality of filters arranged in an array, and in the Z direction, the plurality of filters are aligned one by one with the plurality of photodiodes. The filter may be used to filter out visible light outside a predetermined wavelength. For example, the filter may be used to filter out visible light other than red wavelength, green wavelength, or blue wavelength that reaches the photodiode.

[0090] In the embodiment of the present disclosure, the image sensor 200 may further include a plurality of micro lenses arranged in an array on the filter. Figure 2In the Z direction, a plurality of micro-lenses are aligned one by one with a plurality of photodiodes. The micro-lenses can be used to converge incident light from outside the image sensor so that the light is focused on the photodiodes aligned therewith.

[0091] It should be noted that Figure 2 and Figure 3 The image sensors illustrated in the figure are all front-illuminated image sensors, and the image sensors involved in the embodiments of the present disclosure also include back-illuminated image sensors. The back-illuminated image sensor includes a stacked circuit layer, a photodiode layer, a light-transmitting layer, a third dielectric layer and a grid structure. Among them, the photodiode layer is formed in the first semiconductor layer and is located on the front surface of the first semiconductor layer. The first semiconductor layer is located on the circuit layer, and the front surface of the first semiconductor layer is in contact with the surface of the circuit layer. The optical signal can reach the first semiconductor layer through the grid structure, the third dielectric layer, and the light-transmitting layer, and enter the photodiode from the rear surface of the first semiconductor layer. Afterwards, the optical signal reaching the photodiode can be converted into an electrical signal. Here, the specific description of the circuit layer, the first semiconductor layer, the photodiode layer, the light-transmitting layer, the third dielectric layer and the grid structure can be referred to. Figure 2 , I will not go into details here.

[0092] Figure 4 Flow chart of a method for manufacturing an image sensor provided by an embodiment of the present disclosure. Figure 4 As shown, an embodiment of the present disclosure provides a method for manufacturing an image sensor, the manufacturing method comprising:

[0093] Step S401: providing a substrate; the substrate comprises a stacked photodiode layer and a circuit layer; the photodiode layer comprises a plurality of photodiodes arranged in an array;

[0094] Step S402: forming a first dielectric layer on the surface of the substrate; the first dielectric layer has a first surface and a second surface arranged opposite to each other along a stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate;

[0095] Step S403: forming a second dielectric layer on the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving optical signals.

[0096] FIG. 5A to FIG. 5D FIG. 1 is a step diagram of a method for manufacturing an image sensor provided by an embodiment of the present disclosure. Figure 5A As shown, a substrate 501 is provided, and the substrate 501 includes a photodiode layer 502 formed in a first semiconductor layer 507 and located on the front surface of the first semiconductor layer 507, a circuit layer 503 located on the photodiode layer 502, and a second semiconductor layer 510 located on the circuit layer 503. The photodiode layer 502 includes a plurality of photodiodes ( Figure 5AHere, for the detailed description of each structure in the substrate, please refer to Figure 2 , which will not be elaborated here.

[0097] like Figure 5A As shown, a first dielectric layer 505 is formed on the surface of the second semiconductor layer 510, and the first dielectric layer 505 has a first surface 505a and a second surface 505b that are arranged opposite to each other along the Z direction. The first surface 505a of the first dielectric layer 505 is a plane in contact with the second semiconductor layer 510, and the second surface 505b of the first dielectric layer 505 includes a plurality of curved surfaces that are convex in a direction away from the substrate.

[0098] In some embodiments, forming a first dielectric layer on the surface of a substrate includes: forming a first dielectric material layer on the surface of the substrate; performing photolithography on the first dielectric material layer using a mask to form the first dielectric layer; wherein the mask has different transmittances in different regions along its thickness direction.

[0099] FIG. 6A to FIG. 6B This is a schematic diagram of the structure of the photomask provided by the embodiment of the present disclosure in the XY plane. Figure 6B for Fig. 6A A partial enlarged view of Fig. 6A As shown, the mask 600 includes a quartz layer 601 and a chromium metal layer 602 formed on the quartz layer 601. The chromium metal layer 602 includes a plurality of chromium metal structures 603 arranged in an array and having the same structure. The projection of each chromium metal structure 603 on the quartz layer 601 is a circle. Here, each chromium metal structure 603 can form a convex structure or a concave structure in the light-transmitting layer. Figure 6B The chromium metal structure 603 is described in detail. Figure 6B As shown, on the XY plane, the chrome metal structure 603 has different thicknesses in different regions along the Z direction. Here, the chrome metal structure 603 has different thicknesses in different regions. Figure 6B In one example, the thickness of the chrome metal structure 603 at a position close to the central area thereof is greater than the thickness of the chrome metal structure 603 at a position away from the central area thereof, and the thickness of the chrome metal structure 603 changes in a step-wise manner along a direction away from the central area. Thus, the light transmittance of the chrome metal structure 603 at a position close to the central area thereof is less than the light transmittance of the chrome metal structure 603 at a position away from the central area thereof. In another example, the thickness of the chrome metal structure 603 at a position close to the central area thereof is less than the thickness of the chrome metal structure 603 at a position away from the central area thereof. Thus, the light transmittance of the chrome metal structure 603 at a position close to the central area thereof is greater than the light transmittance of the chrome metal structure 603 at a position away from the central area thereof.

[0100] In the disclosed embodiment, the material of the first dielectric layer 505 formed on the surface of the substrate 501 includes a photoresist material. Here, forming the first dielectric layer 505 on the surface of the substrate 501 includes: forming a first dielectric material layer on the surface of the substrate 501, the material of the first dielectric material layer including a photoresist material; performing photolithography on the first dielectric material layer using a photomask 600, and it can be understood that since the above-mentioned photomask 600 has different light transmittances in different regions in the thickness direction, the exposure of different regions of the first dielectric material layer is also different; and developing the first dielectric material layer after photolithography using a developer to form a first dielectric layer 505 having a curved surface (the second surface 505b).

[0101] It can be understood that in the embodiment of the present disclosure, the thickness of the chromium metal structure 603 changes in a stepwise manner at different speeds in the direction away from the central area, which corresponds to different degrees of smoothness of the second surface 505b of the first dielectric layer 505, and also corresponds to different degrees of smoothness of the surface of the convex structure or concave structure in the light-transmitting layer. Therefore, by designing a photomask 600 with a specific thickness change, a first dielectric layer 505 that meets the design requirements can be prepared.

[0102] In some embodiments, forming a first dielectric layer on the surface of a substrate includes: inkjet printing a first dielectric material to form the first dielectric material layer on the surface of the substrate; and curing the first dielectric material layer to form the first dielectric layer.

[0103] In the disclosed embodiment, the material of the first dielectric layer 505 formed on the surface of the substrate 501 includes an organic material. Here, inkjet printing the first dielectric material to form the first dielectric material layer on the surface of the substrate includes: using a tiny nozzle to spray the first dielectric material in liquid state on the surface of the substrate 501 to form a first dielectric material layer in liquid state on the surface of the substrate 501. It should be noted that since the surface of the substrate 501 is the second semiconductor layer 510, the second semiconductor layer 510 is easily oxidized during the preparation process of the image sensor to form an oxide layer on its surface, and the oxide layer is a natural oleophobic layer. Therefore, the first dielectric material layer formed by inkjet printing will have a larger wetting angle on the oxide layer, so that the first dielectric material layer is in the shape of a raised water drop. After the first dielectric material layer is formed, the first dielectric material layer can be cured, for example, the first dielectric material layer is cured using a curing agent to form a first dielectric layer 505 in the shape of a raised water drop. At this time, the first surface 505 a of the first dielectric layer 505 is a plane, and the second surface 505 b of the first dielectric layer 505 is a curved surface.

[0104] like Figure 5BAs shown, after forming the first dielectric layer 505, a second dielectric layer 506 is formed on the second surface 505b of the first dielectric layer 505 by a deposition process. The material of the second dielectric layer 506 includes a high dielectric constant material. The second dielectric layer can be used as a voltage adjustment layer and a reflective layer to improve the optical performance of the image sensor. In some embodiments, the refractive index of the material of the first dielectric layer 505 is different from the refractive index of the material of the second dielectric layer 506. In this way, a plurality of microlens structures for converging light are formed in the first dielectric layer 505, thereby improving the imaging quality of the image sensor in a dark light environment. Here, since the second surface 505b of the first dielectric layer 505 is a curved surface, the surface of the second dielectric layer 506 formed on the first dielectric layer 505 is also a curved surface. In this way, the second dielectric layer 506 can have a larger light receiving surface, so that it can receive more light signals.

[0105] In some embodiments, the manufacturing method of the image sensor also includes: forming a third dielectric layer on the surface of the second dielectric layer; flattening the surface of the third dielectric layer; forming a grid structure on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each photodiode in the photodiode layer in the stacking direction.

[0106] like Figure 5C As shown, after forming the second dielectric layer 506, a deposition process may be used to form a third dielectric layer 512 on the surface of the second dielectric layer 506. Here, since the surface of the second dielectric layer 506 is a curved surface, the surface of the third dielectric layer 512 formed on the second dielectric layer 506 is also a curved surface. At this time, a chemical mechanical polishing process may be used to planarize the surface of the third dielectric layer 512 so that the third dielectric layer 512 has a flat surface.

[0107] In the embodiment of the present disclosure, the deposition process for forming the second dielectric layer 506 and the third dielectric layer 512 includes but is not limited to physical vapor deposition, chemical vapor deposition, and atomic layer deposition.

[0108] like Figure 5D As shown, after the surface of the third dielectric layer 512 is planarized, a grid structure 513 can be formed on the surface of the third dielectric layer 512 by using a patterning process. The grid structure 513 has a plurality of defined cavities 514 that are aligned one by one with each photodiode in the photodiode layer 502 in the Z direction. In this way, the grid structure 513 can isolate the optical signals incident on each photodiode from each other, thereby reducing signal crosstalk.

[0109] It should be noted that FIG. 5A to FIG. 5D The manufacturing method of the front-illuminated image sensor is only used as an example for description. The manufacturing method of the embodiment of the present disclosure can also be applied to a back-illuminated image sensor.

[0110] The disclosed embodiment provides an image sensor, which includes: a substrate, the substrate includes a stacked photodiode layer and a circuit layer; a light-transmitting layer, the light-transmitting layer is located on the surface of the substrate; the light-transmitting layer includes a first dielectric layer and a second dielectric layer; wherein the first dielectric layer has a first surface and a second surface arranged opposite to each other along the stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate; the second dielectric layer covers the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving light signals. In the disclosed embodiment, the first surface of the first dielectric layer is a plane, and the second surface of the first dielectric layer is a curved surface. In this way, the first dielectric layer forms a microlens structure in the light-transmitting layer for converging light. The microlens structure can capture a larger amount of incoming light, thereby improving the imaging quality of the image sensor in a dark light environment.

[0111] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present disclosure. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present disclosure, the size of the serial number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure. The serial numbers of the embodiments of the present disclosure are for description only and do not represent the advantages and disadvantages of the embodiments.

[0112] The above description is only a preferred embodiment of the present disclosure, and does not limit the patent scope of the present disclosure. All equivalent structural changes made by using the contents of the present disclosure and the drawings under the inventive concept of the present disclosure, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present disclosure.

Claims

1. An image sensor, It is characterized in that include: A substrate, the substrate comprising a stacked photodiode layer and a circuit layer; A light-transmitting layer, wherein the light-transmitting layer is located on the surface of the substrate; The light-transmitting layer comprises a first dielectric layer and a second dielectric layer; wherein the first dielectric layer has a first surface and a second surface arranged opposite to each other along a stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate; The second dielectric layer covers the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving optical signals.

2. The image sensor according to claim 1, It is characterized in that The light-transmitting layer includes a plurality of protruding structures protruding in a direction away from the substrate; or, the light-transmitting layer includes a plurality of concave structures concave in a direction away from the substrate.

3. The image sensor according to claim 2, It is characterized in that The second surface of the first dielectric layer includes a plurality of curved surfaces protruding in a direction away from the substrate, and the thickness of the second dielectric layer is uniform at all locations; the first dielectric layer and the second dielectric layer together constitute a plurality of the protruding structures.

4. The image sensor according to claim 2, It is characterized in that The second surface of the first dielectric layer includes a plurality of curved surfaces recessed toward the substrate, and the thickness of the second dielectric layer is uniform at all locations; the first dielectric layer and the second dielectric layer together constitute a plurality of recessed structures.

5. The image sensor according to claim 2, It is characterized in that The image sensor further comprises: A third dielectric layer, the third dielectric layer covers the second dielectric layer; and a surface of the third dielectric layer is a plane.

6. The image sensor according to claim 5, It is characterized in that The photodiode layer includes a plurality of photodiodes arranged in an array; The image sensor further comprises: A grid structure is located on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each of the photodiodes in the photodiode layer in the stacking direction.

7. The image sensor according to claim 6, It is characterized in that In the stacking direction, each of the photodiodes is aligned with one of the protruding structures or one of the recessed structures; or, each of the photodiodes is aligned with a plurality of the protruding structures or a plurality of the recessed structures.

8. The image sensor according to any one of claims 1 to 7, It is characterized in that The refractive index of the material of the first dielectric layer is different from the refractive index of the material of the second dielectric layer.

9. The image sensor according to any one of claims 1 to 7, It is characterized in that The material of the first dielectric layer includes a photoresist material and an organic material, and the material of the second dielectric layer includes a high dielectric constant material.

10. A method for manufacturing an image sensor, It is characterized in that include: providing a substrate; The substrate comprises a stacked photodiode layer and a circuit layer; the photodiode layer comprises a plurality of photodiodes arranged in an array; forming a first dielectric layer on the surface of the substrate; The first dielectric layer has a first surface and a second surface which are arranged opposite to each other along a stacking direction, the first surface is a plane close to the substrate, and the second surface is a curved surface away from the substrate; A second dielectric layer is formed on the second surface of the first dielectric layer; the surface of the second dielectric layer is a curved surface for receiving optical signals.

11. The manufacturing method according to claim 10, It is characterized in that The step of forming a first dielectric layer on the surface of the substrate comprises: forming a first dielectric material layer on the surface of the substrate; The first dielectric material layer is photolithographically processed using a photomask to form the first dielectric layer; wherein the photomask has different light transmittances in different regions along its thickness direction.

12. The manufacturing method according to claim 10, It is characterized in that The step of forming a first dielectric layer on the surface of the substrate comprises: inkjet printing the first dielectric material to form a first dielectric material layer on the surface of the substrate; The first dielectric material layer is cured to form the first dielectric layer.

13. The manufacturing method according to claim 10, It is characterized in that The manufacturing method further comprises: forming a third dielectric layer on a surface of the second dielectric layer; performing a planarization process on the surface of the third dielectric layer; A grid structure is formed on the surface of the third dielectric layer; the grid structure has a plurality of defined cavities aligned one by one with each of the photodiodes in the photodiode layer in the stacking direction.

14. The manufacturing method according to any one of claims 10 to 13, It is characterized in that The material of the first dielectric layer includes a photoresist material and an organic material, and the material of the second dielectric layer includes a high dielectric constant material.

15. The manufacturing method according to any one of claims 10 to 13, It is characterized in that The refractive index of the material of the first dielectric layer is different from the refractive index of the material of the second dielectric layer.

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