Image sensor and manufacturing method thereof

Abstract

The invention provides an image sensor and a manufacturing method thereof, and relates to semiconductor manufacturing. The photoelectric sensing area in the image sensor can be formed by a plurality of doped deposition layers. Therefore, ion implantation does not need to be carried out in the preparation process of the photoelectric sensing area, and damage of ion implantation to the substrate is avoided. In addition, the atomic mass of the doping ions of the bottom doped deposition layer in the multiple doped deposition layers is large, a groove is formed in the bottom doped deposition layer, the atomic mass of the doping ions of the top doped deposition layer is relatively small, and the groove formed in the bottom doped deposition layer is filled with the doping ions of the top doped deposition layer. Therefore, the stability of the photoelectric sensing area can be ensured by arranging the doped ions with relatively high atomic mass at the bottom, and meanwhile, the doped deposition layer can be filled with a large amount of doped ions with relatively low atomic mass through the grooves, so that more free electrons are provided, the light current of the photodiode during light sensing is improved, and the photoelectric sensing efficiency is improved. Therefore, the light sensing capability of the image sensor is improved.

Description

Technical Field

[0001] The present application relates to semiconductor manufacturing, and in particular to an image sensor and a method for manufacturing the same. Background Art

[0002] Image sensors are devices that convert light signals into electrical signals and are widely used in photography, security systems, smart phones, fax machines, scanners, medical electronics, etc. Among them, CMOS (complementary metal oxide semiconductor) sensors are a widely used image sensor.

[0003] With the widespread application of image sensors, CMOS sensors are also constantly improving. Back Side Illumination (BSI) image sensors are a special type of CMOS image sensors that place photosensitive elements on the back of the chip, allowing light to directly illuminate the photosensitive layer, thereby improving light receiving efficiency and image quality.

[0004] In the traditional BSI process, high-energy ion implantation is used in the front-end process to form the photoelectric sensing area, which will cause damage (damage to the substrate surface) and cause cross talk (cross talk) undesirable effects. Therefore, how to optimize the structure and manufacturing of the photoelectric sensing area of ​​the BSI sensor is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of this, an embodiment of the present application provides an image sensor and a method for manufacturing the same, which forms a doping layer in a photoelectric sensing region by vapor deposition without the need for ion implantation into the substrate, thereby avoiding damage to the substrate caused by ion implantation.

[0006] In a first aspect, the present application provides an image sensor. The image sensor includes at least a substrate, a shallow trench isolation structure, an isolation layer, a photosensitive region isolation structure, a first doped deposition layer, and a second doped deposition layer. The shallow trench isolation structure extends from the bottom surface of the substrate into the substrate. The isolation layer contacts one end of the shallow trench isolation structure in the substrate. The photosensitive region isolation structure is arranged on the isolation layer and corresponds to the shallow trench isolation structure, and a photoelectric sensing region is formed between adjacent photosensitive region isolation structures. The first doped deposition layer is arranged on the isolation layer and is located in the photoelectric sensing region, and the first doped deposition layer is away from the top of the photosensitive region isolation structure to form a top groove. The second doped deposition layer is arranged on the first doped deposition layer and fills the top groove of the first doped deposition layer. The second doped deposition layer includes a plurality of doped sublayers with different doping ions, and each doped sublayer selects doped ions with relatively reduced atomic mass along the direction close to the first doped deposition layer, and the ion type of the doped ions of the first doped deposition layer and the second doped deposition layer is the same, and the atomic mass of the doped ions of the first doped deposition layer is greater than the atomic mass of the doped ions of the doped sublayer close to the first doped deposition layer in the second doped deposition layer.

[0007] Optionally, the second doped deposition layer includes a flat-top doped sublayer and at least one intermediate doped sublayer. The intermediate doped sublayer forms a sublayer top groove away from the top of the first doped deposition layer, and forms a sublayer bottom protrusion near the bottom of the first doped deposition layer to fill the top groove of the underlying doped layer, and the depth of the sublayer top groove of the intermediate doped sublayer is less than the thickness of the sublayer bottom protrusion. The flat-top doped sublayer is away from the first doped deposition layer and presents a flat surface at the top away from the first doped deposition layer, and the bottom is filled with the sublayer top groove of at least one intermediate doped sublayer.

[0008] Optionally, the first doped deposition layer is configured as an antimony-doped silicon deposition layer, the flat top doped sublayer is configured as an antimony-doped silicon deposition layer, and at least one intermediate doped sublayer includes an arsenic-doped silicon deposition layer and a phosphorus-doped silicon deposition layer, and the phosphorus-doped silicon deposition layer is close to the first doped deposition layer.

[0009] Optionally, the photosensitive area isolation structure includes a metal reflective layer close to the isolation layer, and the first doped deposition layer covers the metal reflective layer.

[0010] Optionally, the first doped deposition layer includes a sidewall residual region close to the photosensitive region isolation structure and a dry-etched region away from the photosensitive region isolation structure. The top height of the dry-etched region is lower than the top height of the sidewall residual region, and a top groove is formed in the dry-etched region.

[0011] Optionally, the image sensor further includes a filter structure disposed on the second doped deposition layer, and the top of the filter structure is in an arc shape protruding outward.

[0012] In a second aspect, the present application provides a method for manufacturing an image sensor. The manufacturing method includes: providing a substrate, wherein the substrate is provided with a shallow trench isolation structure extending from the bottom surface of the substrate into the substrate and an isolation layer in contact with one end of the shallow trench isolation structure in the substrate. A photosensitive region isolation structure is formed on the isolation layer, and the photosensitive region isolation structure corresponds to the shallow trench isolation structure and a photoelectric sensing region is formed between adjacent photosensitive region isolation structures. The photoelectric sensing region on the isolation layer is vapor-deposited based on doped ions to form a first doped deposition layer. The first doped deposition layer is etched, and a top groove is formed at the top of the first doped deposition layer away from the photosensitive region isolation structure. A second doped deposition layer is vapor-deposited based on doped ions on the top of the first doped deposition layer to form a second doped deposition layer. The second doped deposition layer includes a plurality of doped sublayers with different doped ions, and each doped sublayer selects doped ions with relatively reduced atomic mass along the direction close to the first doped deposition layer, and the ion type of the doped ions of the first doped deposition layer and the second doped deposition layer is the same, and the atomic mass of the doped ions of the first doped deposition layer is greater than the atomic mass of the doped ions of the doped sublayer in the second doped deposition layer close to the first doped deposition layer.

[0013] Optionally, the second doped deposition layer includes a flat-top doped sublayer and at least one intermediate doped sublayer, and vapor deposition is performed on the top of the first doped deposition layer based on doping ions to form the second doped deposition layer, including: vapor deposition is performed on the top of the first doped deposition layer or the intermediate doped layer below to form a target intermediate doped sublayer. Etching the target intermediate doped sublayer, and forming a sublayer top groove at the top of the target intermediate doped sublayer away from the first doped deposition layer, wherein the target intermediate doped sublayer forms a sublayer bottom protrusion near the bottom of the first doped deposition layer to fill the top groove of the doped layer below, and the depth of the sublayer top groove of the target intermediate doped sublayer is less than the thickness of the sublayer bottom protrusion. Vapor deposition is performed on the top of at least one intermediate doped sublayer based on doping ions to form a flat-top doped sublayer, wherein the flat-top doped sublayer is away from the first doped deposition layer and has a flat surface at the top away from the first doped deposition layer, and the bottom fills the sublayer top groove of at least one intermediate doped sublayer.

[0014] Optionally, the first doped deposition layer is etched to form a top groove at the top of the first doped deposition layer away from the photosensitive area isolation structure, including: etching the first doped deposition layer using a dry etching process to form a sidewall residual area close to the photosensitive area isolation structure and a dry etching area away from the photosensitive area isolation structure in the first doped deposition layer, wherein the top height of the dry etching area is lower than the top height of the sidewall residual area, and a top groove is formed in the dry etching area.

[0015] Optionally, the manufacturing method further includes: forming a filter structure on the second doped deposition layer, wherein the top of the filter structure is in an arc shape protruding outward.

[0016] Based on the image sensor and its manufacturing method provided by the embodiment of the present application, the photoelectric sensing area in the image sensor can be formed by multiple doped deposition layers. As a result, the photoelectric sensing area does not need to be implanted with ions during the preparation process, thereby avoiding the damage to the substrate caused by ion implantation. In addition, among the aforementioned multiple doped deposition layers, the atomic mass of the doped ions in the bottom doped deposition layer is relatively large and a groove is formed in the bottom doped deposition layer, while the atomic mass of the doped ions in the top doped deposition layer is relatively small and fills the groove formed by the aforementioned bottom doped deposition layer. As a result, the stability of the photoelectric sensing area can be ensured by arranging doped ions with higher atomic mass at the bottom, while doped ions with smaller atomic mass can be filled in large quantities in the doped deposition layer through the aforementioned grooves to provide more free electrons, thereby increasing the photocurrent when the photodiode is sensitive to light, thereby improving the image sensor's ability to perceive light. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a schematic diagram of the structure of an image sensor provided in some embodiments of the present application.

[0019] Figure 2 This is another structural schematic diagram of an image sensor provided in some embodiments of the present application.

[0020] Figure 3 This is another structural schematic diagram of an image sensor provided in some embodiments of the present application.

[0021] Figure 4 is an exemplary flow chart of a method for manufacturing an image sensor provided in some embodiments of the present application.

[0022] Figure 5 It is a schematic diagram of the structure of the substrate provided in some embodiments of the present application.

[0023] Figure 6 It is a schematic diagram of the structure of a substrate without an isolation layer provided in some embodiments of the present application.

[0024] Figure 7 It is a schematic diagram of the structure of a substrate after ion implantation provided in some embodiments of the present application.

[0025] Figure 8It is a structural schematic diagram of the photosensitive area isolation structure provided in some embodiments of the present application.

[0026] Fig. 9 It is a schematic diagram of the structure of the epitaxial layer of the photosensitive area isolation structure provided in some embodiments of the present application.

[0027] Fig.10 It is a structural schematic diagram of the deposition structure of the first doped deposition layer provided in some embodiments of the present application.

[0028] Fig.11 It is a schematic diagram of the structure of the first doped deposition layer provided in some embodiments of the present application.

[0029] Fig.12 It is a schematic diagram of the structure of the second doped deposition layer provided in some embodiments of the present application.

[0030] Fig.13 It is a schematic diagram of the structure of the filter structure provided in some embodiments of the present application.

[0031] Fig.14 It is a structural schematic diagram of the isolation extension structure provided in some embodiments of the present application.

[0032] Fig.15 This is an exemplary process of a method for manufacturing a second doped deposition layer provided in some embodiments of the present application.

[0033] Fig.16 It is a structural schematic diagram of a deposition structure of an intermediate doped sublayer provided in some embodiments of the present application.

[0034] Fig.17 This is a schematic diagram of the structure of an intermediate doped sublayer provided in some embodiments of the present application.

[0035] Fig.18 This is a schematic diagram of the structure of another intermediate doped sublayer provided in some embodiments of the present application.

[0036] Among them, 100, image sensor; 110, substrate; 111, shallow trench isolation structure; 112, isolation layer; 120, photosensitive area isolation structure; 121, isolation extension structure; 130, first doped deposition layer; 131, top groove; 132, sidewall residual area; 133, dry etching area; 140, second doped deposition layer; 141, flat-top doped sublayer; 142, middle doped sublayer; 1421, sublayer top groove; 1422, sublayer bottom protrusion; 150, filter structure. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner, and 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 form, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0039] 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.

[0040] Application Overview: In a back-illuminated sensor, after the light beam enters the back-illuminated sensor, it will be directly sensed by the photoelectric sensing area (Photodiode, PD, also known as photodiode), and then the photoelectric sensing area will sense the intensity of the incident light, thereby forming a photocurrent under specific conditions, which will be sensed and transmitted by the metal wiring layer below.

[0041] In the traditional back-illuminated sensor manufacturing, the photoelectric sensing area is generally realized by high-energy particle injection (also known as ion implantation), that is, P-type ions can be injected into the silicon substrate to form the photoelectric sensing area. Therefore, when photons are absorbed by the PN junction in the semiconductor material, the photon energy causes the electrons in the valence band to transition to the conduction band, forming electron-hole pairs. These electron-hole pairs drift in opposite directions under the action of the internal electric field, generating photocurrent.

[0042] However, in the actual preparation process, high-energy ion implantation will damage the lattice structure of the semiconductor material, generating a large number of defects such as vacancies and interstitial atoms, which will affect the performance of the material.

[0043] In particular, in the aforementioned back-illuminated sensor, the light beam is filtered before entering the photoelectric sensing area, that is, the aforementioned photoelectric sensing area will only sense the intensity of the corresponding light beam. However, when ion implantation is used, the silicon lattice is destroyed, and the photocurrent generated by the photoelectric sensing area of ​​a pixel unit may be transmitted to the adjacent pixel unit along with the destroyed lattice, thereby generating crosstalk between different pixel units.

[0044] To solve the above problems, in the image sensor provided by the present application, the photoelectric sensing area can be formed by multiple doped deposition layers. That is, the photoelectric sensing area is formed on the substrate by a vapor deposition process, and its doping is directly performed during the deposition process. Therefore, the photoelectric sensing area does not need to be ion implanted during the preparation process, avoiding the damage of the substrate by ion implantation.

[0045] In addition, in order to further optimize the photocurrent of the photoelectric sensing area, the present application further optimizes the stacking structure of the doped deposition layer in the photoelectric sensing area. Specifically, among the aforementioned multiple doped deposition layers, the atomic mass of the doped ions in the bottom doped deposition layer is relatively large and a groove is formed in the bottom doped deposition layer, while the atomic mass of the doped ions in the top doped deposition layer is relatively smaller and fills the groove formed by the aforementioned bottom doped deposition layer. Thus, the stability of the photoelectric sensing area can be ensured by arranging doped ions with higher atomic mass at the bottom, while doped ions with smaller atomic mass can be filled in large quantities in the doped deposition layer through the aforementioned grooves to provide more free electrons, thereby increasing the photocurrent of the photodiode when it is sensitive to light, thereby improving the image sensor's ability to perceive light.

[0046] To further illustrate the aforementioned image sensor and the method for manufacturing the same, various non-limiting embodiments of the present application will be specifically introduced below with reference to the accompanying drawings.

[0047] Example Image Sensors: The image sensor provided in the present application may be a back-illuminated sensor, but it is understandable that part of the structure of the semiconductor device provided in the present application may be migrated and used for other semiconductor configurations.

[0048] Figure 1 This is a schematic diagram of the structure of an image sensor provided in some embodiments of the present application.

[0049] like Figure 1 As shown, the image sensor 100 includes a substrate 110 , a shallow trench isolation structure 111 , an isolation layer 112 , a photosensitive region isolation structure 120 , a first doped deposition layer 130 , and a second doped deposition layer 140 .

[0050] The substrate 110 may be a silicon substrate. Considering the specific structure of the back-illuminated sensor, a metal wiring layer may be provided on one side of the substrate 110, and a photoelectric sensing area may be provided on the other side. In this application, one side of the photoelectric sensing area is regarded as the upper side for description. The metal wiring layer below the substrate 110 may be provided according to relevant technologies, and this application will not further illustrate it.

[0051] The shallow trench isolation structure 111 may be an isolation structure for isolating each pixel unit in the substrate 110, and it may extend into the substrate along the bottom surface (the lower surface) of the substrate 110. The front shallow trench isolation structure 111 may generally be realized by etching and filling the substrate 110. For example, based on the distribution of the pixel units, etching may be performed at the position between the pixel units in the substrate 110 and then silicon oxide may be deposited to realize the shallow trench isolation structure 111 between each pixel unit, so as to realize electrical isolation between the pixel units. The depth of the shallow trench isolation structure 111 is 55nm to 60nm.

[0052] The isolation layer 112 may be an electrical isolation layer between the photoelectric sensing region and the metal wiring layer, and the thickness of the isolation layer is 3 nm to 5 nm.

[0053] In the image sensor 100 provided in the present application, the substrate 110 may only involve the aforementioned shallow trench isolation structure 111 and the isolation layer 112, so that the aforementioned other structures are formed on the substrate 110 without processing the inside of the substrate 110. For example, for the isolation layer 112 formed by the aforementioned ion implantation, after the isolation layer 112 is formed, the excess substrate above the isolation layer 112 may be ground to expose the isolation layer 112.

[0054] The photosensitive region isolation structure 120 may be an isolation structure on the substrate 110 for isolating each pixel unit, that is, it can be understood as a deep trench isolation structure disposed on the upper surface of the substrate 110. It may be on the aforementioned isolation layer 112 and aligned with the setting position of the shallow trench isolation structure 111 and extend upward to isolate the photoelectric sensing area of ​​each pixel unit. That is, the photosensitive region isolation structure 120 is disposed on the isolation layer 112 and corresponds to the shallow trench isolation structure 111, and a photoelectric sensing area is formed between adjacent photosensitive region isolation structures.

[0055] The photosensitive area isolation structure 120 can generally be realized by vapor deposition and etching, that is, a plurality of extension layers corresponding to the photosensitive area isolation structure 120 are generally deposited first, and then the plurality of extension layers are etched based on the arrangement of the pixel units to leak out the isolation layer 112 of the photoelectric sensing area of ​​each pixel unit.

[0056] The doped deposition layer may refer to a silicon deposition layer doped with specific ions formed based on a vapor deposition process. Among them, the doped deposition layer involved in the present application may be based on group VA element doping, that is, the doped ions include one of the group VA elements, such as nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) and molybdenum (Mc). In addition, the same ion type of the doped ions referred to in the present application may mean that the ions doped in the present application are all one of the group VA elements.

[0057] In actual manufacturing, volatile Group VA impurities can be introduced into the gas flow through solution doping technology, thereby doping the corresponding Group VA elements when depositing silicon.

[0058] The first doped deposition layer 130 may refer to a deposition layer located at the bottom layer among the plurality of doped deposition layers, that is, the first doped deposition layer 130 is disposed on the isolation layer 112 and is located in the photoelectric sensing region.

[0059] Considering the stability requirements of the device, the doping ions of the first doping deposition layer 130 can be configured as elements with relatively large atomic mass, such as antimony (Sb), bismuth (Bi) and molybdenum (Mc) mentioned above. Therefore, based on the larger atomic mass of the bottom, it has stronger stability. If a photocurrent is generated, its atoms will not be driven in a short time, thereby generating crosstalk.

[0060] Further considering that the doping ions of the aforementioned first doping deposition layer 130 can be configured to have a relatively large atomic mass and be relatively inert, the space occupied by the first doping deposition layer 130 can be reduced as much as possible to accommodate more active doping ions. Thus, the aforementioned first doping deposition layer 130 forms a top groove 131 away from the top of the photosensitive region isolation structure 120.

[0061] That is, after the first doped deposition layer 130 is deposited during vapor deposition, the first doped deposition layer 130 may be etched to form a top groove 131 in the central region of the top surface thereof.

[0062] A plurality of doped deposition layers may be disposed on the first doped deposition layer 130, and the doped deposition layer above the first doped deposition layer 130 may be collectively referred to as the second doped deposition layer 140. That is, the second doped deposition layer 140 is disposed on the first doped deposition layer 130 and fills the top groove 131 of the first doped deposition layer 130.

[0063] Considering that the second doped deposition layer 140 may include multiple layers, the doping ions of each layer may be selected based on the principle mass to improve the performance of the photocurrent. The second doped deposition layer 140 includes multiple doping sublayers with different doping ions and each doping sublayer selects doping ions with relatively decreasing atomic mass along the direction close to the first doped deposition layer 130.

[0064] Therefore, the atomic mass of each doping layer in the aforementioned second doping deposition layer 140 forms a design that decreases from top to bottom. This design can reduce the resistance of the material by reducing the atomic mass of the doping layer, thereby improving the current transmission efficiency, thereby optimizing the photon absorption efficiency and current transmission performance.

[0065] For example, the second doping deposition layer 140 may include doping sub-layers doped with antimony (Sb), arsenic (As), and phosphorus (P) in order from top to bottom.

[0066] Further considering the requirements of the doping ions and the protective effect of the aforementioned first doping deposition layer 130, the ion type of the doping ions in the first doping deposition layer 130 and the second doping deposition layer 140 is the same and the atomic mass of the doping ions in the first doping deposition layer 130 is greater than the atomic mass of the doping ions in the doping sublayer of the second doping deposition layer 140 close to the first doping deposition layer 130.

[0067] For example, the doping ions of the aforementioned first doped deposition layer 130 may be antimony (Sb), then the doping ions of the doped sublayer in the second doped deposition layer 140 close to the first doped deposition layer 130 should be elements in Group VA whose atomic mass is less than antimony (Sb), such as nitrogen (N), phosphorus (P), and arsenic (As).

[0068] Thus, the photoelectric sensing area in the aforementioned image sensor 100 can be formed by multiple doped deposition layers. Thus, the photoelectric sensing area does not need to be implanted with ions during the preparation process, thereby avoiding damage to the substrate 110 caused by ion implantation. In addition, among the aforementioned multiple doped deposition layers, the atomic mass of the doped ions in the bottom doped deposition layer is relatively large and a groove is formed in the bottom doped deposition layer, while the atomic mass of the doped ions in the top doped deposition layer is relatively small and fills the groove formed by the aforementioned bottom doped deposition layer. Thus, the stability of the photoelectric sensing area can be ensured by arranging doped ions with higher atomic mass at the bottom, while doped ions with smaller atomic mass can be filled in large quantities in the doped deposition layer through the aforementioned grooves to provide more free electrons, thereby increasing the photocurrent of the photodiode when it is sensitive to light, thereby improving the image sensor 100's ability to perceive light.

[0069] In some embodiments, the image sensor 100 may also be provided with a filter layer for filtering light and a microlens structure for absorbing light. In the present application, the filter layer and the microlens structure may be integrated into a filter structure.

[0070] That is, the image sensor 100 may further include a filter structure 150 disposed on the second doped deposition layer 140, and the top of the filter structure 150 is in an arc shape protruding outward. That is, the filter structure 150 may be in the form of a microlens structure for focusing light, and may be constructed based on a filter material, thereby forming a two-in-one structure of filtering and focusing light.

[0071] In some embodiments, continue to refer to the aforementioned Figure 1 The top groove 131 can be realized by dry etching. Specifically, the first doped deposition layer 130 includes a sidewall residual region 132 close to the photosensitive region isolation structure 120 and a dry etching region 133 away from the photosensitive region isolation structure 120 .

[0072] Specifically, considering that it is necessary to deposit multiple doped deposition layers on the aforementioned first doped deposition layer 130, when depositing the first doped deposition layer 130, the first doped deposition layer 130 does not completely fill the recessed area formed by the photosensitive region isolation structure 120. During dry etching, considering the etching conditions of the etching gas in the recessed area, the etching gas will gather in the central area of ​​the recessed area, while the density at the edge is lower. Therefore, when etching the aforementioned first doped deposition layer 130, the portion close to the side wall (i.e., the aforementioned photosensitive region isolation structure 120) is etched less to form the aforementioned side wall residual area 132, while the central area will form the aforementioned dry etching area 133 due to the sufficient gathering and etching of the etching gas.

[0073] Based on the etching logic, the top height of the dry-etched area 133 is lower than the top height of the sidewall residual area 132, and a top groove 131 is formed in the dry-etched area 133. Specifically, considering the etching conditions, the top groove 131 may be in the shape of an inverted trapezoid with a flat bottom.

[0074] Thus, the top groove 131 of the aforementioned first doped deposition layer 130 can be directly realized based on the dry etching process, without complicated processing, which reduces the difficulty of its preparation. In addition, the proportion and depth of each of the aforementioned regions can be adjusted by adjusting the process parameters of the dry etching process, so as to prepare the first doped deposition layer 130 that meets the requirements.

[0075] In some embodiments, to increase the light sensing capability and the isolation capability between pixel units, a metal reflective layer (such as aluminum) may be provided in the aforementioned photosensitive region isolation structure 120. Thus, the large-angle light beam in the pixel unit will be refracted by the metal reflective layer to ensure that it is within the pixel unit.

[0076] When the doped deposition layer contacts the aforementioned metal reflective layer, the photocurrent may be conducted by the aforementioned metal reflective layer to the adjacent pixel unit. To avoid this situation, the inert property and protective effect of the aforementioned first doped deposition layer 130 may be utilized to make the first doped deposition layer 130 cover the metal reflective layer, that is, the height of the sidewall residual region 132 in the first doped deposition layer 130 (such as the distance to the isolation layer 112 in the vertical direction) may be higher than the height of the metal reflective layer, thereby achieving coverage of the metal reflective layer.

[0077] Therefore, considering that the atomic mass in the first doped deposition layer 130 is large and its electron migration ability is poor, the speed at which the electrons generated by it are transferred to the metal reflective layer is slow. Furthermore, the concentration of the first doped deposition layer 130 can be reduced, thereby reducing the number of electrons generated based on the concentration effect, so that the electrons generated by it will not immediately reach the metal reflective layer and be transmitted, thereby reducing crosstalk.

[0078] In summary, the aforementioned first doped deposition layer 130 can also be understood as a protective layer formed by the upper doped deposition layer to prevent the more active upper doped deposition layer from contacting the outside, thereby reducing crosstalk and improving stability.

[0079] To further illustrate the internal structure of the second doped deposition layer, the present application also provides another structural schematic diagram of an image sensor ( Figure 2 ).exist Figure 2 The detailed internal structure of the second doped deposition layer 140 is shown in FIG.

[0080] like Figure 2 As shown, structurally, the second doping deposition layer 140 may include two types of doping sub-layers, wherein the second doping deposition layer 140 may include a flat top doping sub-layer 141 and at least one middle doping sub-layer 142 .

[0081] The top surface of the intermediate doped sublayer 142 is similar to the aforementioned first doped deposition layer 130, and a sublayer top groove 1421 is also formed on its top. Considering that both the intermediate doped sublayer 142 and the first doped deposition layer 130 are provided with top grooves, the bottom surfaces of the doped layers provided on the intermediate doped sublayer 142 and the first doped deposition layer 130 need to fill the grooves below.

[0082] Considering that the intermediate doped sub-layer 142 is closer to the first doped deposition layer 130 , the bottom of each intermediate doped sub-layer 142 needs to fill the top groove of the underlying doped layer, thereby forming a sub-layer bottom protrusion 1422 .

[0083] In order to ensure that more doping ions are deposited on the intermediate doped sublayer 142, the thickness of the intermediate doped sublayer 142 between the aforementioned groove 1421 at the top of the sublayer and the protrusion 1422 at the bottom of the sublayer should be greater than the thickness of the edge of the intermediate doped sublayer 142 where no groove is formed. That is, the depth of the groove 1421 at the top of the intermediate doped sublayer 142 is less than the thickness of the protrusion 1422 at the bottom of the sublayer, thereby ensuring that more material is deposited on the protrusion 1422 at the bottom of the sublayer.

[0084] In particular, the ratio of the thickness of the edge of the intermediate doped sublayer 142 where no groove is formed to the thickness of the intermediate doped sublayer 142 at the groove can be controlled to be 1:3. Generally, the edge thickness is 20nm and the middle thickness is 60nm. In addition, when there are multiple intermediate doped sublayers 142, multiple intermediate doped sublayers 142 can be realized by controlling the depth of the groove.

[0085] The flat-top doped sublayer 141 may be the topmost deposition layer of the second doped deposition layer 140, and it should have a flat surface and fill the groove below. That is, the flat-top doped sublayer 141 is away from the first doped deposition layer 130 and has a flat surface at the top away from the first doped deposition layer 130, and the bottom is filled with at least one sublayer top groove 1421 of the intermediate doped sublayer 142.

[0086] Therefore, based on the above design, the intermediate doped sublayer 142 can deposit more doping ions when the contact area with the photosensitive region isolation structure 120 is smaller.

[0087] Preferably, the aforementioned first doped deposition layer 130 is configured as an antimony-doped silicon deposition layer, the flat-top doped sublayer 141 is configured as an antimony-doped silicon deposition layer, and at least one intermediate doped sublayer 142 includes an arsenic-doped silicon deposition layer and a phosphorus-doped silicon deposition layer, and the phosphorus-doped silicon deposition is closer to the first doped deposition layer 130.

[0088] It should be noted that Figure 2 This is only an exemplary structure of the second doped deposition layer. In actual implementation, it only needs to meet the aforementioned atomic mass requirements, and is not limited to Figure 2 For example, the present application also provides a structural diagram of an image sensor ( Figure 3 ).

[0089] Figure 3 Another image sensor was demonstrated, different from Figure 2 The image sensor 100 shown, Figure 3The second doped deposition layer of the image sensor includes two doped sublayers both in contact with the first doped deposition layer. One doped sublayer is in contact with the sidewall residual area of ​​the first doped deposition layer, and the other doped sublayer is in contact with the dry-etched area (i.e., the top groove). Thus, the image sensor of the present application can be realized by setting the doped ions of the two doped sublayers without forming the aforementioned Figure 2 The structure shown.

[0090] An exemplary method of manufacturing an image sensor: To further illustrate the manufacturing method of the aforementioned image sensor 100, the present application also provides an exemplary flow chart of the manufacturing method of the image sensor ( Figure 4 ).

[0091] like Figure 4 As shown, the manufacturing method P200 may include the following steps: S210, providing a substrate.

[0092] S220, forming a photosensitive area isolation structure on the isolation layer.

[0093] S230 , performing vapor deposition based on doping ions in the photoelectric sensing region on the isolation layer to form a first doped deposition layer.

[0094] S240, etching the first doped deposition layer to form a top groove at the top of the first doped deposition layer away from the photosensitive region isolation structure.

[0095] S250 , performing vapor deposition based on doping ions on top of the first doped deposition layer to form a second doped deposition layer.

[0096] To further describe the aforementioned P200, the following Figures 5 to 14 The aforementioned steps are described in detail.

[0097] In the aforementioned S210, the substrate 110 may be Figure 5 The structure shown. Figure 5 In the embodiment, the substrate 110 is provided with a shallow trench isolation structure 111 extending from the bottom surface of the substrate 110 into the substrate 110 and an isolation layer 112 contacting one end of the shallow trench isolation structure 111 in the substrate 110 .

[0098] The relationship between the isolation layer 112 and the substrate 110 can be determined according to the actual preparation process of the substrate 110. That is, the isolation layer 112 can be formed in the aforementioned substrate 110 or on the substrate 110 according to its preparation method. For another example, when the aforementioned shallow trench isolation structure 111 is formed, the substrate can be ground to expose the shallow trench isolation structure 111, and the aforementioned isolation layer 112 can be formed on it by deposition.

[0099] For another example, ion implantation can be used. For example, boron ions can be implanted above the shallow trench isolation structure 111 to form an isolation layer 112. Thus, the isolation layer 112 is in contact with one end of the shallow trench isolation structure 111 in the substrate 110. The implantation energy can be 30 KeV. The implantation dose can be 1E15 to 5E15 atom / cm 3 .

[0100] The isolation layer 112 is prepared by the ion implantation method. The substrate 110 before forming the isolation layer 112 can be seen in FIG. Figure 6 The substrate 110 after forming the isolation layer 112 can be seen in Figure 7 .for Figure 7 The substrate 110 shown may be polished by a chemical mechanical polishing (CMP) process to remove structures above the isolation layer 112 .

[0101] In the aforementioned S220, based on Figure 5 The substrate 110 is processed as shown, thereby forming a Figure 8 The photosensitive region isolation structure 120 is shown.

[0102] In some embodiments, the aforementioned photosensitive region isolation structure 120 can be realized by deposition / epitaxial growth and then etching. Figure 8 Before the photosensitive region isolation structure 120 is shown, a Fig. 9 The epitaxial layer of the photosensitive isolation structure shown.

[0103] like Fig. 9 As shown, the epitaxial layer of the photosensitive region isolation structure 120 may be composed of a multi-layer structure, which includes silicon oxide, titanium nitride, aluminum, and tantalum pentoxide from top to bottom.

[0104] In the photosensitive area isolation structure 120, silicon oxide (SiO2) is usually used as a dielectric layer or part of a deep trench isolation structure to provide optical isolation and electrical insulation. In the deep trench isolation structure, silicon oxide can fill the trench to prevent light leakage and ensure independence between pixels. Titanium nitride (TiN) mainly plays the role of a diffusion barrier layer in the isolation structure to prevent diffusion between aluminum and silicon oxide. In addition, titanium nitride can also be used as an adhesion layer to improve the adhesion during deposition (such as the phosphorus-doped silicon deposition layer in the subsequent second doped deposition layer 140). Aluminum (Al) is mainly used as a metal reflective layer. Tantalum pentoxide (Ta2O5) is a high dielectric constant material that can be used to manufacture high-k dielectric layers. In the isolation structure, it may be used to improve electrical insulation performance, thereby enhancing electrical isolation between pixel units.

[0105] exist Fig. 9Different epitaxial layers can be grown layer by layer to form Fig. 9 After the epitaxial layer shown, mask etching can be performed to form Figure 8 The photosensitive region isolation structure 120 is shown to ensure that the photosensitive region isolation structure 120 is aligned with the aforementioned shallow trench isolation structure 111 to separate the photoelectric sensing regions of each pixel unit.

[0106] In the aforementioned S230, the aforementioned Figure 8 The photosensitive region isolation structure 120 is vapor deposited to form Fig.10 The deposition structure of the first doped deposition layer 130 is shown. The deposition structure of the first doped deposition layer 130 may refer to a deposition result formed by vapor deposition to form the first doped deposition layer 130 .

[0107] In some embodiments, considering that the first doped deposition layer 130 needs to cover the aforementioned metal reflective layer and needs to be etched later, during the aforementioned deposition, the deposition height of the first doped deposition layer 130 can be higher than the aforementioned metal reflective layer to ensure that the metal reflective layer is still covered after etching.

[0108] In the aforementioned S240, the aforementioned Fig.10 The deposition structure of the first doped deposition layer 130 is etched to form Fig.11 A first doped deposition layer 130 is shown.

[0109] In some embodiments, the aforementioned first doped deposition layer 130 can be directly implemented based on mask lithography, that is, a mask is formed based on the grooves of the first doped deposition layer 130 and then the top groove 131 is etched based on the mask.

[0110] In order to simplify the etching process of the top groove 131, the top groove 131 can also be realized by dry etching. That is, the first doped deposition layer 130 is etched by dry etching process, and the sidewall residual area 132 close to the photosensitive region isolation structure 120 and the dry etching area 133 away from the photosensitive region isolation structure 120 are formed in the first doped deposition layer 130.

[0111] Considering that the top height of the dry-etched region 133 is lower than the top height of the sidewall residual region 132, a top groove 131 is formed in the dry-etched region 133. The specific principle of this process can be found in the above content, and will not be described here.

[0112] In the aforementioned S250, it is possible to Fig.11 The first doped deposition layer 130 is further deposited and etched to Fig.12 A second doped deposition layer 140 is shown.

[0113] In some embodiments, the second doped deposition layer 140 generally fills the photosensitive region isolation structure 120. To achieve a flat interface, after depositing the second doped deposition layer 140, a CMP process may be performed to make the top surface of the second doped deposition layer 140 flush with the top of the photosensitive region isolation structure 120.

[0114] In some embodiments, considering the filter layer and the microlens array of the image sensor 100, the aforementioned P200 may further include the following steps: S260, forming a filter structure on the second doped deposition layer.

[0115] The aforementioned S260 can Fig.12 The second doped deposition layer 140 is processed to form Fig.13 The filter structure 150 is shown. Considering that the filter structure 150 has a filter function and is a lens structure, its preparation can be realized by partition deposition and pattern transfer. For details, please refer to the relevant technology and will not be described here.

[0116] Further considering the crosstalk between the aforementioned filter structures 150, before forming the filter structure 150, the filter structure 150 can be based on Fig.12 The second doped deposition layer 140 shown extends the photosensitive region isolation structure 120 to form Fig.14 The isolation extension structure 121 is shown to isolate each filter structure 150, thereby forming the aforementioned Fig.13 The light filtering structure 150 is shown.

[0117] The preparation process of the isolation extension structure 121 is the same as that of the photosensitive region isolation structure 120. In some embodiments, the epitaxial layers of the isolation extension structure 121 may include titanium nitride, aluminum, and tantalum pentoxide in order from top to bottom.

[0118] In some embodiments, the combination of conventional filter layers and microlenses can also be based on Fig.14 The isolation extension structure 121 shown is implemented. In which, the filter layer is generally flush with the isolation extension structure 121 to form a flat surface to prepare a microlens array.

[0119] In some embodiments, to further illustrate the aforementioned Figure 2 The present application also provides an exemplary flow chart of a method for manufacturing a second doped deposition layer. Fig.15 ).

[0120] like Fig.15 As shown, the manufacturing method P300 of the second doped deposition layer (ie, the aforementioned S250) may include the following steps: S310 , performing vapor deposition based on doping ions on top of the first doped deposition layer or the lower intermediate doped layer to form a target intermediate doped sublayer.

[0121] S320, etching the target middle doped sub-layer, and forming a top groove at the top of the target middle doped sub-layer away from the first doped deposition layer.

[0122] S330 , performing vapor deposition based on doping ions on top of at least one intermediate doped sublayer to form a flat top doped sublayer.

[0123] To further describe the aforementioned P300, the following Figures 16 to 18 The aforementioned steps are described in detail.

[0124] Considering that the second doped deposition layer 140 may include multiple intermediate doped sublayers, the target intermediate doped sublayer in the aforementioned P300 may refer to the intermediate doped sublayer currently being prepared. According to the actual setting of the intermediate doped sublayer, the first doped deposition layer or the intermediate doped layer (recorded as the lower intermediate doped layer for distinction) may be below it.

[0125] When the doped layer below the target intermediate doped sublayer is the first doped deposition layer 130, the aforementioned S310 may be based on the aforementioned Fig.11 The first doped deposition layer 130 is deposited to form Fig.16 The deposition structure of the intermediate doped sublayer 142 is shown. The aforementioned S320 may be based on Fig.16 The deposited structure shown is etched to form Fig.17 The intermediate doped sublayer 142 in the.

[0126] When the doped layer below the target intermediate doped sublayer is an intermediate doped sublayer, the aforementioned S310 may be based on the aforementioned Fig.17 The intermediate doped sublayer 142 shown is deposited, and then etched through the aforementioned S320 to form Fig.18 The intermediate doped sublayer 142 in the.

[0127] Right now Fig.16 Below the middle doped sublayer 142 is the first doped deposition layer 130. Fig.18 Below the intermediate doped sublayer 142 is still the intermediate doped sublayer 142 .

[0128] Similar to the preparation process of the first doped deposition layer 130 , in the aforementioned S320 , a dry etching process may also be directly used to form the sub-layer top groove 1421 of the intermediate doped sub-layer 142 .

[0129] After each intermediate doped sub-layer 142 is prepared (eg Fig.18 ), the aforementioned S330 may be executed to form Fig.12 (each doped sublayer is considered as a whole) as shown in the flat top doped sublayer 141. As mentioned above, after forming the flat top doped sublayer 141, a CMP process can be used to perform subsequent steps to form Fig.14 or Figure 1 The image sensor shown.

[0130] In some embodiments, in order to ensure that the intermediate doped sublayer 142 deposits more material in the groove area, in the aforementioned intermediate doped sublayer 142, it should be ensured that the depth H1 of the sublayer top groove 1421 of the intermediate doped sublayer 142 is less than the depth H2 of the sublayer bottom protrusion 1422. Let the thickness of the intermediate doped sublayer 142 at the sidewall residual area be D1, then its thickness D2 in the groove area = D1 + H2 - H1, considering the aforementioned H1 < H2, then the aforementioned D2 > D1. Based on the aforementioned D2 ≈ 3D1, this structure can be achieved by designing the thickness of each groove, which will not be described in detail here.

[0131] In summary, the image sensor and the manufacturing method thereof provided by the present application have the following unexpected effects: ① The photoelectric sensing area in the image sensor is formed by multiple doped deposition layers. Therefore, the photoelectric sensing area does not need to be ion implanted during the preparation process, avoiding damage to the substrate during ion implantation.

[0132] ② Among the aforementioned multiple doped deposition layers, the doped ions in the bottom doped deposition layer have a larger atomic mass and form a groove in the bottom doped deposition layer, while the doped ions in the top doped deposition layer have a relatively smaller atomic mass and fill the groove formed by the aforementioned bottom doped deposition layer. Thus, the stability of the photoelectric sensing area can be ensured by setting the doped ions with a higher atomic mass at the bottom, while the doped ions with a smaller atomic mass can be filled in the doped deposition layer in large quantities through the aforementioned grooves to provide more free electrons, thereby increasing the photocurrent of the photodiode when it is sensitive to light, thereby improving the image sensor's ability to perceive light.

[0133] ③ The top layer groove is directly realized by using a dry etching process, which directly utilizes the process defects of the dry etching process and forms a groove through the unetched area of ​​the side wall.

[0134] ④ The first doped deposition layer can serve as a protective base to shield the metal reflective layer, thereby reducing crosstalk based on its atomic mass and concentration effect.

[0135] ⑤ When constructing the photosensitive area isolation structure, the deposition conditions of each doped deposition layer can be considered to provide additional adsorption force for the doped deposition layer that is difficult to deposit. That is, a titanium nitride layer can be set in the photosensitive area isolation structure based on the deposition area of ​​the phosphorus-doped silicon deposition layer to improve the adsorption force of the phosphorus-doped silicon deposition layer.

[0136] ⑥ Through the design of multiple grooves and protrusions, more deposition can be formed in the middle of the doping layer with smaller atomic mass, so as to achieve as much material deposition as possible while keeping the deposition amount near the photosensitive area isolation structure constant.

[0137] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments 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 present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An image sensor, characterized in that: The image sensor comprises: substrate; A shallow trench isolation structure extending from the bottom surface of the substrate into the substrate; an isolation layer, contacting one end of the shallow trench isolation structure in the substrate; A photosensitive region isolation structure is disposed on the isolation layer and corresponds to the shallow trench isolation structure, and a photoelectric sensing region is formed between adjacent photosensitive region isolation structures; A first doped deposition layer is disposed on the isolation layer and is located in the photoelectric sensing region, wherein the first doped deposition layer is away from the top of the photosensitive region isolation structure to form a top groove; a second doped deposition layer, disposed on the first doped deposition layer and filling a top groove of the first doped deposition layer; The second doped deposition layer includes a plurality of doped sublayers with different doped ions, and each doped sublayer selects doped ions with relatively decreasing atomic mass along the direction approaching the first doped deposition layer, the first doped deposition layer and the second doped deposition layer have the same ion type of doped ions, and the atomic mass of the doped ions in the first doped deposition layer is greater than the atomic mass of the doped ions in the doped sublayer of the second doped deposition layer close to the first doped deposition layer.

2. The image sensor according to claim 1, characterized in that The second doped deposition layer includes a flat top doped sublayer and at least one intermediate doped sublayer; The intermediate doped sublayer forms a sublayer top groove away from the top of the first doped deposition layer, and forms a sublayer bottom protrusion close to the bottom of the first doped deposition layer to fill the top groove of the underlying doped layer, and the depth of the sublayer top groove of the intermediate doped sublayer is less than the thickness of the sublayer bottom protrusion; The flat-top doped sublayer is away from the first doped deposition layer and presents a flat surface at the top away from the first doped deposition layer, and the bottom is filled with the sublayer top groove of the at least one intermediate doped sublayer.

3. The image sensor according to claim 2, characterized in that The first doped deposition layer is configured as an antimony-doped silicon deposition layer, the flat-top doped sublayer is configured as an antimony-doped silicon deposition layer, and the at least one intermediate doped sublayer includes an arsenic-doped silicon deposition layer and a phosphorus-doped silicon deposition layer, and the phosphorus-doped silicon deposition layer is close to the first doped deposition layer.

4. The image sensor according to claim 1, characterized in that The photosensitive area isolation structure includes a metal reflective layer close to the isolation layer, and the first doped deposition layer covers the metal reflective layer.

5. The image sensor according to claim 1, characterized in that The first doped deposition layer includes a sidewall residual region close to the photosensitive region isolation structure and a dry-etched region away from the photosensitive region isolation structure; The top height of the dry-etched region is lower than the top height of the sidewall residual region, and a top groove is formed in the dry-etched region.

6. The image sensor according to claim 1, characterized in that: The image sensor further includes a filter structure disposed on the second doped deposition layer, and the top of the filter structure is in an arc shape protruding outward.

7. A method for manufacturing an image sensor, characterized in that: The manufacturing method comprises: A substrate is provided, wherein the substrate is provided with a shallow trench isolation structure extending from a bottom surface of the substrate into the substrate and an isolation layer contacting one end of the shallow trench isolation structure in the substrate; A photosensitive region isolation structure is formed on the isolation layer, wherein the photosensitive region isolation structure corresponds to the shallow trench isolation structure and a photoelectric sensing region is formed between adjacent photosensitive region isolation structures; Performing vapor deposition on the photoelectric sensing region on the isolation layer based on doping ions to form a first doped deposition layer; Etching the first doped deposition layer to form a top groove at the top of the first doped deposition layer away from the photosensitive region isolation structure; Performing vapor deposition based on doping ions on top of the first doped deposition layer to form a second doped deposition layer; Among them, the second doped deposition layer includes multiple doped sublayers with different doped ions, and each doped sublayer selects doped ions with relatively decreasing atomic mass along the direction close to the first doped deposition layer, the first doped deposition layer and the second doped deposition layer have the same ion type of doped ions, and the atomic mass of the doped ions in the first doped deposition layer is greater than the atomic mass of the doped ions in the doped sublayer of the second doped deposition layer close to the first doped deposition layer.

8. The manufacturing method according to claim 7, characterized in that: The second doped deposition layer includes a flat-top doped sublayer and at least one intermediate doped sublayer, and the second doped deposition layer is formed by vapor deposition based on doping ions on the top of the first doped deposition layer, including: Performing vapor deposition based on doping ions on top of the first doped deposition layer or the lower intermediate doped layer to form a target intermediate doped sublayer; Etching the target intermediate doped sublayer to form a sublayer top groove at the top of the target intermediate doped sublayer away from the first doped deposition layer, wherein the target intermediate doped sublayer forms a sublayer bottom protrusion close to the bottom of the first doped deposition layer to fill the top groove of the underlying doped layer, and the depth of the sublayer top groove of the target intermediate doped sublayer is less than the thickness of the sublayer bottom protrusion; The flat-top doped sublayer is formed by vapor deposition based on doping ions on the top of the at least one intermediate doped sublayer, wherein the flat-top doped sublayer is away from the first doped deposition layer and has a flat surface at the top away from the first doped deposition layer, and the bottom is filled with a sublayer top groove of the at least one intermediate doped sublayer.

9. The manufacturing method according to claim 7, characterized in that: The etching of the first doped deposition layer to form a top groove at the top of the first doped deposition layer away from the photosensitive region isolation structure includes: The first doped deposition layer is etched by a dry etching process, and a sidewall residual area close to the photosensitive area isolation structure and a dry etching area away from the photosensitive area isolation structure are formed in the first doped deposition layer, wherein the top height of the dry etching area is lower than the top height of the sidewall residual area, and a top groove is formed in the dry etching area.

10. The manufacturing method according to claim 7, characterized in that: The manufacturing method further comprises: A filter structure is formed on the second doped deposition layer, wherein the top of the filter structure is in an arc shape protruding outwards.

Images