CN109256403B - Front-illuminated image sensor and method of forming the same - Google Patents
Front-illuminated image sensor and method of forming the same Download PDFInfo
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- CN109256403B CN109256403B CN201710573378.4A CN201710573378A CN109256403B CN 109256403 B CN109256403 B CN 109256403B CN 201710573378 A CN201710573378 A CN 201710573378A CN 109256403 B CN109256403 B CN 109256403B
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- 230000003287 optical effect Effects 0.000 claims abstract description 75
- 239000004065 semiconductor Substances 0.000 claims abstract description 46
- 239000000758 substrate Substances 0.000 claims abstract description 41
- 239000000463 material Substances 0.000 claims abstract description 16
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 18
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(iv) oxide Chemical compound O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 claims description 18
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 18
- 238000005530 etching Methods 0.000 claims description 13
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- 229910052710 silicon Inorganic materials 0.000 claims description 12
- 239000010703 silicon Substances 0.000 claims description 12
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 8
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 8
- 238000005498 polishing Methods 0.000 claims description 3
- 229910000449 hafnium oxide Inorganic materials 0.000 claims 1
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 claims 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
- H10F39/80—Constructional details of image sensors
- H10F39/811—Interconnections
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
- H10F39/011—Manufacture or treatment of image sensors covered by group H10F39/12
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
- H10F39/10—Integrated devices
- H10F39/12—Image sensors
- H10F39/18—Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
- H10F39/80—Constructional details of image sensors
- H10F39/806—Optical elements or arrangements associated with the image sensors
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Abstract
The invention relates to a front-illuminated image sensor and a forming method thereof, comprising the steps of providing a semiconductor substrate, wherein the semiconductor substrate is formed with a photodiode area corresponding to a pixel unit; the method for forming the at least one metal interconnection layer comprises the steps of forming an optical dense medium area above the photodiode area, forming a metal layer around the optical dense medium area, and forming an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area. The process method is compatible with the conventional CMOS semiconductor process, has simple process, can independently allocate the refractive index, the morphology and the like of the optically dense medium region according to the design requirement, and has flexible design. In addition, by adding the dense medium material with high refractive index on the photodiode region, the light guide tube is used, and the loss of the obtained light signal caused by reflection and refraction is reduced, so that the sensitivity of the image sensor is improved, and the crosstalk is reduced.
Description
Technical Field
The present disclosure relates to image sensors, and particularly to a front-illuminated image sensor and a method for forming the same.
Background
The image sensor is a sensor capable of sensing optical image information and converting it into a usable output signal, and is an important component constituting a digital camera. According to the element, two kinds of elements, namely, a CCD (Charge Coupled Device ) and a CMOS (Complementary Metal-oxide semiconductor, metal oxide semiconductor) are classified. With the continuous development of CMOS integrated circuit manufacturing processes, particularly CMOS image sensor design and manufacturing processes, CMOS image sensors have gradually replaced CCD image sensors as the mainstream. Compared with the CMOS image sensor, the CMOS image sensor has the advantages of higher industrial integration level, lower power and the like.
CMOS image sensor products can be classified into FSI (FrontSide Illumination, front-illuminated) and BSI (BackSide Illumination, back-illuminated). In front-end-of-line CMOS image sensor products, BEOL (Back RndOf Line, back-end-of-line) processes have at least two layers of metal wiring, i.e., metal lines and dielectric layers comprising multiple layers. For the photosensitive area, the distance from the chip surface to the photosensitive surface is relatively large, so that incident light rays can be absorbed by the photosensitive area only by a longer path, not only is light rays attenuated greatly, but also CRA (CHIEF RAY ANGLE, included angle between main light rays and normal direction of an imaging surface) of the chip cannot be too large, and therefore wide application of the image sensor is affected.
In addition, due to the existence of different dielectric layers, light rays can be reflected and refracted in the process of transmission, so that light is lost, energy is reduced, the number of electrons reaching the bottom of the photodiode from the surface of the chip is reduced, the sensitivity of the light is reduced, and the performance of the image sensor is influenced.
Disclosure of Invention
The invention aims to provide a front-illuminated image sensor and a forming method thereof, which solve the problem of light loss in the light propagation process of the image sensor in the prior art and improve the sensitivity.
In order to solve the above technical problems, the present invention provides a method for forming a front-illuminated image sensor, including:
providing a semiconductor substrate, wherein the semiconductor substrate is formed with a photodiode region corresponding to a pixel unit;
forming a plurality of metal interconnection layers on the semiconductor substrate;
the method for forming the at least one metal interconnection layer comprises the steps of forming an optical dense medium area above the photodiode area, forming a metal layer around the optical dense medium area, and forming an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area.
Optionally, the cross-sectional shape of the optically dense medium region is regular trapezoid or triangle.
Optionally, the refractive index of the optically dense medium is at least 15% greater than the refractive index of the optically hydrophobic medium.
Optionally, the material of the optical dense medium is one of silicon nitride, silicon oxynitride, silicon carbide and hafnium dioxide or a combination thereof.
Optionally, the material of the photophobic medium is one or a combination of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide and hafnium dioxide.
Optionally, 2-4 metal interconnection layers are formed on the semiconductor substrate.
Optionally, the method for forming the metal interconnection layers from the first layer to the secondary top layer further comprises forming a through hole structure for connecting adjacent metal interconnection layers in the photophobic medium region.
Optionally, the forming method of the metal interconnection layer of at least one layer includes:
Forming a light-tight medium on the semiconductor substrate, etching the light-tight medium, and reserving a part of the light-tight medium above the photodiode region;
Forming a metal layer covering the rest semiconductor substrate and the optical dense medium, etching the metal layer, and reserving part of the metal layer around the optical dense medium;
forming an optical and sparse medium covering the metal layer and the optical and dense medium, and chemically and mechanically polishing the optical and sparse medium to expose the top of the optical and dense medium.
Optionally, the method for forming the metal interconnection layer from the first layer to the secondary top layer further comprises the steps of etching the photophobic medium to form a groove exposing part of the metal layer, and filling metal in the groove to form a through hole structure.
Optionally, the width of the dense medium region is less than or equal to the width of the photodiode region.
Accordingly, another aspect of the present invention also provides a front-illuminated image sensor, including:
a semiconductor substrate formed with a photodiode region corresponding to a pixel unit;
a plurality of metal interconnection layers formed on the semiconductor substrate;
the at least one metal interconnection layer is provided with an optical dense medium area formed above the photodiode area, a metal layer positioned around the optical dense medium area and an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area.
Optionally, the cross-sectional shape of the optically dense medium region is regular trapezoid or triangle.
Optionally, the refractive index of the optically dense medium is at least 15% greater than the refractive index of the optically hydrophobic medium.
Optionally, the material of the optical dense medium is one of silicon nitride, silicon oxynitride, silicon carbide and hafnium dioxide or a combination thereof.
Optionally, the material of the photophobic medium is one or a combination of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide and hafnium dioxide.
Optionally, 2-4 metal interconnection layers are formed on the semiconductor substrate.
Optionally, the first layer to the sub-top metal interconnection layer further comprises a through hole structure formed in the photophobic medium region and connected with the adjacent metal interconnection layer.
Optionally, the width of the dense medium region is less than or equal to the width of the photodiode region.
Compared with the prior art, the front-illuminated image sensor and the forming method thereof have the following beneficial effects:
The method for forming the at least one metal interconnection layer comprises the steps of forming an optical dense medium area above the photodiode area, forming a metal layer around the optical dense medium area, and forming an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area. The process method is compatible with the conventional CMOS semiconductor process, has simple process, can independently allocate the refractive index, the morphology and the like of the optically dense medium region according to the design requirement, and has flexible design.
In addition, by adding the dense medium material with high refractive index on the photodiode region, the light guide tube is used, and the loss of the obtained light signal caused by reflection and refraction is reduced, so that the sensitivity of the image sensor is improved, and the crosstalk is reduced.
Drawings
FIG. 1 is a flow chart of a front-illuminated image sensor forming method according to an embodiment of the invention;
FIG. 2 is a flowchart illustrating a method of forming a metal interconnect layer according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of a semiconductor substrate according to an embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view of an embodiment of the invention for forming an optical density medium;
FIG. 5 is a schematic cross-sectional view of the remaining optical density medium in an embodiment of the present invention;
FIG. 6 is a schematic cross-sectional view illustrating a metal layer formed according to an embodiment of the invention;
FIG. 7 is a schematic cross-sectional view of a remaining metal layer according to an embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of an optical-hydrophobic medium according to an embodiment of the present invention;
FIG. 9 is a schematic cross-sectional view of a residual photo-hydrophobic medium according to an embodiment of the present invention;
FIG. 10 is a schematic cross-sectional view illustrating the formation of a trench in an embodiment of the present invention;
FIG. 11 is a schematic cross-sectional view of a via structure formed according to an embodiment of the invention;
fig. 12 is a schematic cross-sectional view of a multi-layered metal interconnect formed in accordance with an embodiment of the present invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than those herein described, and those skilled in the art will readily appreciate that the present invention may be similarly embodied without departing from the spirit or essential characteristics thereof, and therefore the present invention is not limited to the specific embodiments disclosed below.
Next, the present invention will be described in detail with reference to the drawings, which are only examples for convenience of illustration, and should not be construed as limiting the scope of the invention.
In order to make the above objects, features and advantages of the present invention more comprehensible, the following detailed description of the front-illuminated image sensor and the forming method thereof will be given with reference to the accompanying drawings.
Referring to fig. 12, the front-illuminated image sensor provided by the invention comprises a semiconductor substrate 10, a plurality of metal interconnection layers 30, 40 and 50 formed on the semiconductor substrate 10, at least one metal interconnection layer 30, 40 or 50, a dense medium region 31', 41 or 51 formed above the photodiode region 11, a metal layer 32', 42 or 52 positioned around the dense medium region 31', 41 or 51, and a dense medium region 33', 43 or 53 covering the metal layer and surrounding the dense medium region, wherein the semiconductor substrate 10 is formed with a photodiode region 11 corresponding to a pixel unit.
Referring to fig. 1, the method for forming a front-illuminated image sensor of the present invention includes the steps of:
Step S1 is performed, and referring to fig. 3, a semiconductor substrate 10 is provided, and the semiconductor substrate 10 is formed with a plurality of Photodiode (PD) regions 11 corresponding to Pixel cells (pixels). The surface of the semiconductor substrate 10 has an insulating layer 20 and a via structure 21 in the insulating layer 20, the insulating layer 20 is used for protecting the device structure in the semiconductor substrate 10, and the via structure 21 is used for electrically leading out the device structure in the semiconductor substrate 10.
In step S2, referring to fig. 12, in the back-end process, a plurality of metal interconnect layers are formed on the semiconductor substrate 10, and 2 to 4 metal interconnect layers are formed on the semiconductor substrate 10, for example, in this embodiment, a description is given of forming 3 metal interconnect layers on the semiconductor substrate 10, including a first metal interconnect layer 30, a second metal interconnect layer 40, and a third metal interconnect layer (top metal interconnect layer) 50. The method for forming the at least one metal interconnection layer comprises the steps of forming an optical dense medium area above the photodiode area, forming a metal layer around the optical dense medium area, and forming an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area.
In the invention, the refractive index of the optical dense medium is at least more than 15% greater than that of the optical dense medium, for example, the refractive index of the optical dense medium is more than 20% greater than that of the optical dense medium, and the optical dense medium material with high refractive index is added on the photodiode region to play the role of a light guide, so that the optical signal loss caused by reflection and refraction in the optical medium layer is reduced, thereby improving the sensitivity of the image sensor and reducing crosstalk. The material of the optical dense medium is one or a combination of silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC) and hafnium oxide (HfO 2). The material of the photophobic medium is one or a combination of silicon oxide (SiO 2), silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC) and hafnium dioxide (HfO 2).
In addition, in order to realize the electrical connection between the metal interconnection layers of each layer, the forming method of the metal interconnection layers from the first layer to the secondary top layer (the second layer) further comprises the step of forming a through hole structure for connecting the adjacent metal interconnection layers in the photophobic medium region, wherein the through hole structure is electrically connected with the metal layers in the adjacent metal interconnection layers.
Referring to fig. 2, the method for forming the metal interconnection layer of at least one layer specifically includes the following steps:
Step S21 is performed, as shown in fig. 4, by forming a photo-dense medium 31 on the semiconductor substrate 10, etching the photo-dense medium 31, and leaving a portion of the photo-dense medium region 31' above the photodiode region 11, as shown in fig. 5. In this embodiment, conventional photolithography techniques may be used to etch the dense medium, for example, to form a Photoresist (PH) on the dense medium 31, and exposing, developing, etching, removing the photoresist, and so on, to form the dense medium region 31'. The cross-section of the dense medium area 31 'is a regular trapezoid or triangle, for example, the bottom of the regular trapezoid has an angle of 80 °, so that the light is reflected back to the dense medium area 31' as much as possible at the side wall of the dense medium area 31 'after entering the dense medium area 31', and the light enters the photodiode area 11 as much as possible, thereby improving the optical performance of the image sensor. The width of the optically dense medium region 31' is equal to or smaller than the width of the photodiode region 11. The material of the optical dense medium is one or a combination of silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC), and hafnium dioxide (HfO 2), and in this embodiment, the optical dense medium 31 is exemplified by silicon nitride, and the refractive index of the silicon nitride is 1.8-2.0.
Step S22 is performed, referring to fig. 6, to form a metal layer 32 covering the remaining semiconductor substrate 10 and the optical density medium 31', etching the metal layer 32, and leaving a part of the metal layer 32' around the optical density medium 31', where the metal layer 32' is located above the via structure 21 and electrically connected to the via structure 21, to electrically connect to the device structure in the semiconductor substrate 10, referring to fig. 7.
Step S23 is performed, and referring to fig. 8, an optical-hydrophobic medium 33 is formed to cover the metal layer 32', the optical-dense medium 31', and the remaining semiconductor substrate 10. Next, the photo-thinned medium 33 is Chemically Mechanically Polished (CMP), a portion of the photo-thinned medium 33' is left, and etching stops to lift up the photo-dense medium 31', exposing the top of the photo-dense medium 31', as shown with reference to fig. 9. The material of the photo-lyophobic medium is one or a combination of silicon oxide (SiO 2), silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC) and hafnium dioxide (HfO 2), and in this embodiment, the photo-lyophobic medium 33 is exemplified by silicon oxide, and the refractive index of the silicon oxide is 1.4-1.6.
Further, the second metal interconnection layer 40 and the third metal interconnection layer (top metal interconnection layer) 50 are formed on the first metal interconnection layer 30 by the above-described forming method, and the protective layer 60 is formed on the top metal interconnection layer 50. The process method is compatible with the conventional CMOS semiconductor process, has simple process, and can independently allocate the refractive indexes, the morphologies and the like of the light-tight medium areas 31', 41 and 51 in each metal interconnection layer 30, 40 and 50 according to the design requirements, namely, the light-tight medium of each layer can be made of materials with different refractive indexes, the morphologies can be different, and the design is flexible, so that the different design requirements are met. In the invention, the optical dense media 31', 41 and 51 with high refractive index are formed on the photodiode region 11, the refractive index of the optical dense media 31', 41 and 51 is larger than that of the surrounding optical dense media 33', 43 and 53, and the optical dense media play the role of a light guide, so that light forms total reflection in the process of transmitting in a medium layer of a rear-stage process, thereby reducing optical signal loss caused by reflection and refraction, improving the sensitivity of an image sensor and reducing crosstalk.
In addition, in order to realize the electrical connection of the metal interconnection layers 30, 40, 50, the method for forming the metal interconnection layers 30, 40 from the first layer to the second layer (second layer) further comprises etching the photo-hydrophobic medium to form a trench exposing a part of the metal layer, and filling metal in the trench to form a through hole structure. Taking the first metal interconnection layer 30 as an example, a via structure needs to be formed in the photo-hydrophobic medium 33', specifically, first, referring to fig. 10, the photo-hydrophobic medium 33' is etched to form a trench 34 exposing a portion of the metal layer 32', then, referring to fig. 11, the trench 34 is filled with metal to form a via structure 35, and the photo-dense medium 31', the metal layer 32', the photo-hydrophobic medium 33', and the via structure 35 together form the first metal interconnection layer 30. The second metal interconnection layer 40 may be formed into the via structure 45 by the same process, and the structure of the metal interconnection layer in fig. 12 is formed, which is not described herein.
In summary, the invention provides a front-illuminated image sensor and a forming method thereof, comprising providing a semiconductor substrate, forming a photodiode region corresponding to a pixel unit on the semiconductor substrate, forming a plurality of metal interconnection layers on the semiconductor substrate, forming at least one metal interconnection layer by forming an optical dense medium region above the photodiode region, forming a metal layer around the optical dense medium region, and forming an optical sparse medium region covering the metal layer and the periphery of the optical dense medium region. The optical dense medium material with high refractive index is added on the photodiode region to play a role of a light guide, so that the loss of optical signals caused by reflection and refraction is reduced, the sensitivity of the image sensor is improved, and the crosstalk is reduced.
Although the present invention has been described in terms of the preferred embodiments, it is not intended to be limited to the embodiments, and any person skilled in the art can make any possible variations and modifications to the technical solution of the present invention by using the methods and technical matters disclosed above without departing from the spirit and scope of the present invention, so any simple modifications, equivalent variations and modifications to the embodiments described above according to the technical matters of the present invention are within the scope of the technical matters of the present invention.
Claims (15)
1. A method of forming a front-illuminated image sensor, comprising:
providing a semiconductor substrate, wherein the semiconductor substrate is formed with a photodiode region corresponding to a pixel unit;
forming a plurality of metal interconnection layers on the semiconductor substrate;
The method for forming the at least one metal interconnection layer comprises the steps of forming an optical dense medium area above the photodiode area, forming a metal layer around the optical dense medium area, and forming an optical sparse medium area covering the metal layer and the periphery of the optical dense medium area;
The method for forming the metal interconnection layer of at least one layer comprises the following steps:
Forming a light-tight medium on the semiconductor substrate, etching the light-tight medium, and reserving a part of the light-tight medium above the photodiode region;
Forming a metal layer covering the rest semiconductor substrate and the optical dense medium, etching the metal layer, and reserving part of the metal layer around the optical dense medium;
Forming an optical and sparse medium covering the metal layer and the optical and dense medium, and chemically and mechanically polishing the optical and sparse medium to expose the top of the optical and dense medium;
The method for forming the metal interconnection layer from the first layer to the secondary top layer further comprises the steps of etching the photophobic medium to form a groove exposing part of the metal layer, and filling metal in the groove to form a through hole structure.
2. The method of forming a front-illuminated image sensor according to claim 1, wherein the cross-sectional shape of the light-dense medium region is a regular trapezoid or triangle.
3. The method of forming a front-illuminated image sensor according to claim 1, wherein the refractive index of the optically dense medium is at least 15% greater than the refractive index of the optically sparse medium.
4. The method of claim 1, wherein the optical dense medium is one or a combination of silicon nitride, silicon oxynitride, silicon carbide, and hafnium dioxide.
5. The method of claim 1, wherein the material of the photo-hydrophobic medium is one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, hafnium dioxide, or a combination thereof.
6. The method for forming a front-illuminated image sensor according to claim 1, wherein 2-4 metal interconnection layers are formed on the semiconductor substrate.
7. The method of forming a front-illuminated image sensor of claim 1, wherein the method of forming a metal interconnect layer from the first layer to the second-to-top layer further comprises: and forming a through hole structure for connecting adjacent metal interconnection layers in the photophobic medium region.
8. The method of forming a front-illuminated image sensor according to claim 1, wherein the width of the photo-dense dielectric region is equal to or less than the width of the photodiode region.
9. A front-lit image sensor, comprising:
a semiconductor substrate formed with a photodiode region corresponding to a pixel unit;
a plurality of metal interconnection layers formed on the semiconductor substrate;
the at least one metal interconnection layer is provided with an optical density medium area, a metal layer, an optical density medium area and a metal layer, wherein the optical density medium area is formed above the photodiode area;
the optical density medium is formed on the semiconductor substrate, and part of the optical density medium above the photodiode area is reserved through etching;
The metal layer covers the rest semiconductor substrate and the optical density medium, and part of the metal layer around the optical density medium is reserved through etching;
the photophobic medium is covered on the metal layer and the photophobic medium, and the photophobic medium exposes the top through chemical mechanical polishing;
The first layer to the sub-top metal interconnection layer also has a through hole structure formed in the optical-sparse medium region for connecting adjacent metal interconnection layers.
10. The front-illuminated image sensor of claim 9, wherein the cross-sectional shape of the optically dense medium region is a regular trapezoid or triangle.
11. The front-lit image sensor of claim 9, wherein the optical density medium has a refractive index that is at least 15% greater than the refractive index of the optical-hydrophobic medium.
12. The front-illuminated image sensor of claim 9, wherein the material of the optical dense medium is one of silicon nitride, silicon oxynitride, silicon carbide, hafnium dioxide, or a combination thereof.
13. The front-illuminated image sensor of claim 9, wherein the material of the photo-hydrophobic medium is one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, hafnium oxide, or a combination thereof.
14. The front-illuminated image sensor of claim 9, wherein 2-4 metal interconnect layers are formed on the semiconductor substrate.
15. The front-illuminated image sensor of claim 9, wherein the width of the photo-dense dielectric region is less than or equal to the width of the photodiode region.
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