CN112331687A - CMOS image sensor and manufacturing method thereof - Google Patents
CMOS image sensor and manufacturing method thereof Download PDFInfo
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Abstract
The invention provides a CMOS image sensor and a manufacturing method thereof, wherein the CMOS image sensor comprises a substrate, a photodiode, a distributed Bragg reflector and a metal wiring layer, wherein the substrate comprises a front surface and a back surface which are oppositely arranged; the photodiode is positioned in the substrate; the distributed Bragg reflector is positioned on the front surface of the substrate; the metal wiring layer is positioned on one side of the distributed Bragg reflector, which is opposite to the substrate. The invention adopts the distributed Bragg reflector to replace the traditional metal reflector to realize the reflection of near infrared light, is beneficial to reducing the cost, can avoid the related problems of the metal reflector and has more excellent performance. In addition, by combining the deep trench isolation technology and the back scattering technology, the optical path of near infrared light can be further increased, the near infrared light is effectively limited in the photodiode, the absorption enhancement of the near infrared light is realized, the depth of the photodiode is favorably further reduced, and the miniaturization of a pixel device is realized.
Description
Technical Field
The invention belongs to the technical field of image sensors, and relates to a CMOS image sensor and a manufacturing method thereof.
Background
In recent years, the market scale of near-infrared image sensors in the fields of security monitoring, automobile night vision systems and the like is very obvious, and how to enhance the sensitivity of a near-infrared band is an important development direction. However, a CMOS Image Sensor (CIS) based on a silicon-based process has a serious sensitivity attenuation in a red to near infrared band due to a band gap limit of a silicon material itself. Conventional approaches to near-infrared absorption enhancement include thick silicon techniques, doping techniques, etc., without involving material substitution. With the continuous reduction of pixel size, the above method is difficult to meet the requirement. It is important how near-infrared enhancement can be achieved by the design of the device structure without increasing the substrate thickness.
The introduction of an internal reflection mirror structure on the front surface limits the near infrared light to be sufficiently absorbed inside a Photodiode (PD), which is a common structure for realizing near infrared enhancement. Generally, the internal reflector is a metal structure, so that the cost is high, and parasitic effect or electric leakage is easy to exist, and the electrical characteristics of the image sensor are affected.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a CMOS image sensor and a method for fabricating the same, which can solve the problems of the prior art that the cost of the image sensor is high and the electrical characteristics are to be improved.
To achieve the above and other related objects, the present invention provides a back-illuminated CMOS image sensor, comprising:
a substrate including a front surface and a back surface disposed opposite to each other;
a photodiode in the substrate;
the distributed Bragg reflector is positioned on the front surface of the substrate;
and the metal wiring layer is positioned on one surface of the distributed Bragg reflector, which is back to the substrate.
Optionally, the distributed bragg reflector includes at least one group of two-layer structures stacked in a vertical direction, the two-layer structures including a first insulating layer and a second insulating layer sequentially stacked in the vertical direction, and a refractive index of the first insulating layer is smaller than a refractive index of the second insulating layer.
Optionally, the first insulating layer comprises SiO2A layer of the second insulating layer comprising Si3N4Layer and TiO2One of the layers.
Optionally, the distributed bragg reflector comprises 2-100 sets of the double-layer structure stacked in a vertical direction.
Optionally, the backside illuminated CMOS image sensor further comprises a deep trench isolation structure penetrating the substrate in a vertical direction.
Optionally, the material of the deep trench isolation structure includes SiO2At least one of a high-K dielectric and a metal.
Optionally, the backside illuminated CMOS image sensor further includes a backside scattering structure, which penetrates through the backside of the substrate in the vertical direction and extends toward the front side of the substrate.
Optionally, the refractive index of the back scattering structure is less than the refractive index of the substrate.
Optionally, the material of the back scattering structure includes Si3N4And SiO2One kind of (1).
Optionally, the horizontal cross section of the back scattering structure is circular, cross-shaped or zigzag.
Optionally, a vertical projection of the back scattering structure on a horizontal plane is located in a region where the photodiode is located, and a preset distance is formed between one end of the back scattering structure facing the front surface of the substrate and the photodiode.
Optionally, the backside illuminated CMOS image sensor further includes an optical filter and a micro lens, the optical filter is located on the back side of the substrate, and the micro lens is connected to the optical filter.
The invention also provides a manufacturing method of the CMOS image sensor, which comprises the following steps:
providing a substrate, wherein the substrate comprises a front surface and a back surface which are oppositely arranged;
forming a photodiode in the substrate from a front side of the substrate;
forming a distributed Bragg reflector on the front surface of the substrate;
and forming a metal wiring layer on one surface of the distributed Bragg reflector, which is back to the substrate.
Optionally, a first insulating layer and a second insulating layer are alternately deposited at least once on the front surface of the substrate to obtain the distributed bragg reflector, and the refractive index of the first insulating layer is smaller than that of the second insulating layer.
Optionally, the first insulating layer comprises SiO2A layer of the second insulating layer comprising Si3N4Layer and TiO2One of the layers.
Optionally, the method of forming the distributed bragg reflector comprises plasma enhanced chemical vapor deposition.
Optionally, the method further comprises the step of forming a deep trench isolation structure:
providing a substrate, and bonding the substrate and the metal wiring layer;
thinning the substrate from the back side of the substrate;
forming a first trench in the substrate from a backside of the substrate, the first trench penetrating the substrate in a vertical direction;
forming a first filling material in the first trench to obtain the deep trench isolation structure.
Optionally, the method further comprises the step of forming a back scattering structure:
forming a second groove in the substrate from the back surface of the substrate, wherein the second groove is opened from the back surface of the substrate, extends towards the front surface of the substrate and does not reach the front surface of the substrate;
and forming a second filling material in the second groove to obtain the back scattering structure.
Optionally, the refractive index of the back scattering structure is less than the refractive index of the substrate.
Optionally, a vertical projection of the back scattering structure on a horizontal plane is located in a region where the photodiode is located, and a preset distance is formed between one end of the back scattering structure facing the front surface of the substrate and the photodiode.
Optionally, the method further comprises the following steps:
forming an optical filter on the back of the substrate;
and forming a micro lens which is connected with the optical filter.
As described above, the back-illuminated CMOS image sensor and the method for manufacturing the same according to the present invention use a Distributed Bragg Reflector (DBR) instead of a conventional metal reflector to reflect near-infrared light, and the DBR structure has the advantages of: (1) an insulating layer is originally required to be prepared between the front-section photodiode and the rear-section metal wiring, and relevant functions can be realized only by making the insulating layer into a DBR structure. (2) In the present invention, the DBR can adopt multilayer SiO2And Si3N4The periodic structure is compatible with the CMOS process, and the problems related to a metal reflector are avoided. In addition, by combining a Deep Trench Isolation (DTI) technology and a Back Scattering Technology (BST), the optical path of the near-infrared light can be further increased, the near-infrared light is effectively limited inside the PD, and the absorption enhancement of the near-infrared light is realized.
Drawings
Fig. 1 is a schematic cross-sectional view of a CMOS image sensor according to the present invention.
Fig. 2 is a basic structural diagram of a 4T pixel.
Fig. 3 is a process flow chart of a method for fabricating a CMOS image sensor according to the present invention.
Fig. 4 is a schematic view showing a substrate provided for a method of fabricating a CMOS image sensor according to the present invention.
Fig. 5 is a schematic diagram illustrating a method for fabricating a CMOS image sensor according to the present invention, in which a photodiode is formed in a substrate from a front surface of the substrate.
Fig. 6 is a schematic diagram illustrating a method for fabricating a CMOS image sensor according to the present invention, in which a distributed bragg reflector is formed on a front surface of the substrate.
Fig. 7 is a schematic diagram illustrating a metal wiring layer formed on a surface of the dbr mirror opposite to the substrate according to the method for fabricating a CMOS image sensor of the present invention.
Fig. 8 is a schematic diagram illustrating a substrate provided for the method of fabricating a CMOS image sensor according to the present invention and bonding the substrate to the metal wiring layer.
Fig. 9 is a schematic diagram illustrating the formation of deep trench isolation structures and back scattering structures in the method for fabricating a CMOS image sensor according to the present invention.
Fig. 10 is a schematic view illustrating a method for fabricating a CMOS image sensor according to the present invention, in which a filter is formed on a back surface of a substrate and a microlens connected to the filter is formed.
Description of the element reference numerals
1 substrate
101 front side
102 back side
2 photodiode
3 distributed Bragg reflector
301 first insulating layer
301 second insulating layer
4 metal wiring layer
401 dielectric layer
402 conductive line layer
5P trap
6N well
7 surface P type heavily doped region
8N type heavily doped well
9 transfer gate
10 reset transistor
11 source follower
12 selection transistor
13 back scattering structure
14 deep trench isolation structure
15 optical filter
16 micro lens
17 base plate
S1-S4
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 10. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
Referring to fig. 1, a schematic cross-sectional structure of a back-illuminated CMOS image sensor is shown, including a substrate 1, a photodiode 2, a distributed bragg reflector 3, and a metal wiring layer 4, where the substrate 1 includes a front surface 101 and a back surface 102 that are disposed opposite to each other; the photodiode 2 is located in the substrate 1; the Distributed Bragg Reflector (DBR) 3 is positioned on the front surface 101 of the substrate 1; the metal wiring layer 4 is located on a side of the dbr 3 facing away from the substrate 1.
Specifically, the substrate 1 includes, but is not limited to, a silicon substrate, which may be P-type doped or N-type doped. The photodiode 2 is used for receiving light and generating photo-generated electrons, and the distributed Bragg reflector 3 is used for reflecting near infrared light.
By way of example, the CMOS image sensor employs a 4T pixel structure, the pixel being composed of a photodiode 2 and four NMOS type transistors, respectively a transfer transistor MTXReset tube MRSSource follower MSFAnd row gate pipe MSEL. With respect to the 3T pixel structure,the transmission tube and the storage node FD (FD) are added in the 4T pixel structure, so that the relevant double sampling in the true sense is realized, the fixed mode noise is basically eliminated, the random noise is well inhibited, and the dark current on the surface of the pixel is reduced.
As an example, please refer to fig. 2, which shows a basic structure diagram of a 4T pixel, and the basic structure diagram includes a P well 5, an N well 6 formed in the P well 5, a surface P-type heavily doped region 7 formed in the N well 6, an N-type heavily doped well 8 (floating diffusion) located in the P well 5, a transfer gate 9 located above the P well 5, a reset transistor 10 connected to the N-type heavily doped well 8, a source follower 11 connected to the reset transistor 10, and a selection transistor 12 connected to the source follower 11. The P-well 5, the N-well 6 and the P-type heavily doped region 7 form a photodiode 2, the photodiode 2 may be formed by an ion implantation process, and the transfer gate 9, the reset transistor 10, the source follower 11 and the selection transistor 12 may be fabricated by a CMOS process.
As an example, the distributed bragg reflector 3 includes at least one set of two-layer structures stacked in a vertical direction, the two-layer structure including a first insulating layer 301 and a second insulating layer 301 stacked in this order in the vertical direction, and a refractive index of the first insulating layer 301 is smaller than a refractive index of the second insulating layer 302.
Specifically, the principle of Distributed Bragg Reflection (DBR) is: two materials with refractive indexes are arranged alternately in an ABAB mode to form a periodic structure, and the optical thickness n of each layer of materialrD is set to be (1/4+ N) times the central reflection wavelength λ, where d is the macroscopic thickness, N is an integer, N is 0, 1, 2 …, NrIs a refractive index n with respect to vacuum 01. For example, in order to make the central wavelength λ of reflection 900nm, the optical thickness of each layer material is (225+900N) nm. With SiO2Layer as an example, having a refractive index nr1.46, and if N is 0, the formula NrD ═ 1/4 λ, and SiO can be calculated2The macroscopic thickness d of the layer was 154.11 nm.
As an example, the distributed bragg reflector comprises2-100 sets of the double-layer structure stacked in a vertical direction, the first insulating layer 301 including but not limited to SiO2Layer, the second insulating layer 302 including but not limited to Si3N4Layer and TiO2One of the layers. For example, the double-layer structure may be SiO2layer/Si3N4Layer composition, SiO2layer/TiO2Layer combinations, or other suitable combinations.
In this embodiment, the distributed bragg reflector 3 is made of 10 pairs of SiO2layer/Si3N4Layer is for example, wherein SiO2Refractive index of the layer 1.46, Si3N4The refractive index of each layer was 2.05, based on DBR reflection center wavelength 900nm, and each layer was SiO2The thickness of the layers was 154.11nm, each layer of Si3N4The layer-side thickness was 109.76nm, and the total thickness of the distributed Bragg reflector 3 was 2.6 μm. Relative to SiO2layer/TiO2Layer composition of SiO2layer/Si3N4Layer combinations are more compatible with existing processes because of SiO2、Si3N4Is used more in CMOS process.
It should be noted that 10 pairs of periods in this embodiment are merely examples, and in other embodiments, the reflective effect of the DBR mirror can be further improved by increasing the period. In addition, the DBR is used as a dielectric reflector, has no absorption problem of a metal reflector, and has more excellent performance.
As an example, the backside illuminated CMOS image sensor further includes a back scattering structure 13, and the back scattering structure 13 penetrates through the back surface 102 of the substrate 1 in a vertical direction and extends toward the front surface 101 of the substrate 1. In this embodiment, the vertical projection of the back scattering structure 13 on the horizontal plane is located in the region where the photodiode 2 is located, and a preset distance is formed between one end of the back scattering structure 13 facing the front surface 101 of the substrate 1 and the photodiode 2.
Specifically, the refractive index of the back scattering structure 13 is smaller than that of the substrate 1, so that the Near Infrared (NIR) optical path length can be increased by one of diffraction, deflection and reflection, and NIR light can be sufficiently absorbed in the photodiode.
As an example, the material of the back scattering structure 13 includes, but is not limited to, Si3N4And SiO2One kind of (1). The back scattering structures 13 may have different arrangements and shapes according to different requirements, for example, the horizontal cross section of the back scattering structures 13 may be circular, cross-shaped, zigzag-shaped, and the like. The characteristic thickness and the characteristic size of the back scattering structure 13 can be between 0 and 1 micron.
As an example, the back-illuminated CMOS image sensor further includes a deep trench isolation structure 14, the deep trench isolation structure 14 penetrating the substrate 1 in a vertical direction. The deep trench isolation structures 14 are mainly fabricated between pixel units, and mainly function to prevent light from generating crosstalk between pixels and affecting pixel sensitivity. No matter the back scattering structure scatters light or the DBR reflects light, the probability of adjacent pixel crosstalk is increased due to the increase of the light path of the light, and the imaging quality is reduced, so that the DTI plays an important role. The material of the deep trench isolation structure 14 includes but is not limited to SiO2At least one of a high-K dielectric and a metal for reflecting light.
As an example, the back-illuminated CMOS image sensor further includes an optical filter 15 and a micro lens 16, the optical filter 15 is located on the back surface of the substrate 1, and the micro lens 16 is connected to the optical filter 15. Wherein, the incident light enters the substrate 1 through the micro lens 16 and the optical filter 15, and is received by the photodiode 2. The filter 15 may be a red filter, a blue filter or a green filter.
The back-illuminated CMOS image sensor of the embodiment adopts the distributed Bragg reflector to replace the traditional metal reflector to realize the reflection of near infrared light, thereby being beneficial to reducing the cost, avoiding the related problems of the metal reflector and having more excellent performance. In addition, the optical path of near infrared light can be further increased by arranging the back scattering structure and the deep groove isolation structure. The back-illuminated CMOS image sensor adopts the distributed Bragg reflector, the back scattering structure and the deep groove isolation structure, can increase the optical path length of light and improve the near-infrared quantum efficiency under the condition of not increasing the thickness of the substrate (also can be combined with thick silicon), and can further reduce the depth of the photodiode due to the fact that the near-infrared light is effectively limited in the photodiode, thereby being beneficial to realizing the miniaturization of a pixel device in the future.
Example two
Referring to fig. 3, a process flow diagram of a CMOS image sensor manufacturing method is shown, which includes the following steps:
s1: providing a substrate, wherein the substrate comprises a front surface and a back surface which are oppositely arranged;
s2: forming a photodiode in the substrate from a front side of the substrate;
s3: forming a distributed Bragg reflector on the front surface of the substrate;
s4: and forming a metal wiring layer on one surface of the distributed Bragg reflector, which is back to the substrate.
As an example, referring to fig. 4, step S1 is performed: a substrate 1 is provided, the substrate 1 comprising a front side 101 and a back side 102 arranged opposite to each other. The substrate 1 includes, but is not limited to, a silicon substrate, which may be P-type doped or N-type doped.
Referring to fig. 5, step S2 is executed: a photodiode 2 is formed in the substrate 1 from the front surface of the substrate 1 using an ion implantation process.
Referring to fig. 6, step S3 is executed: a distributed bragg reflector 3 is formed on the front surface of the substrate 1.
As an example, a Deposition method, such as Plasma Enhanced Chemical Vapor Deposition (PECVD) or other suitable method, is used to alternately deposit a first insulating layer 301 and a second insulating layer 301 on the front surface 101 of the substrate 1The refractive index of the first insulating layer 301 is smaller than that of the second insulating layer 302 at least once to obtain the distributed bragg reflector 3. In this example, SiO was deposited alternately2layer/Si3N4And carrying out layer 10 times to obtain the distributed Bragg reflector 3. In other embodiments, SiO may also be deposited alternately2layer/TiO2The number of layers, periods may also be adjusted as desired.
Referring to fig. 7, step S4 is executed: and forming a metal wiring layer 4 on one surface of the distributed Bragg reflector 3, which is far away from the substrate 1.
By way of example, the metal wiring layer 4 includes a dielectric layer 401 and at least one conductive line layer 402. The conductive circuit layer 402 can be formed by sputtering, electroplating, etching, or other suitable processes.
Referring to fig. 8, a base plate 17 is further provided, the base plate 17 is bonded to the metal wiring layer 4, and the substrate 1 is thinned from the back side of the substrate 1 by using Chemical Mechanical Polishing (CMP) or other suitable process.
Referring to fig. 9, a deep trench isolation structure 14 and a back scattering structure 13 are further formed.
Specifically, the refractive index of the back scattering structure 13 is smaller than that of the substrate 1, so that the Near Infrared (NIR) optical path length can be increased by one of diffraction, deflection and reflection, and NIR light can be sufficiently absorbed in the photodiode 2. The deep trench isolation structures 14 are mainly fabricated between pixel units, and mainly function to prevent light from generating crosstalk between pixels and affecting pixel sensitivity. No matter the back scattering structure scatters light or the DBR reflects light, the probability of adjacent pixel crosstalk is increased due to the increase of the light path of the light, and the imaging quality is reduced, so that the DTI plays an important role.
As an example, a vertical projection of the back scattering structure 13 on a horizontal plane is located in a region where the photodiode 2 is located, and an end of the back scattering structure 13 facing the front surface of the substrate 1 is spaced from the photodiode 2 by a preset distance.
As an example, forming the deep trench isolation structure 14 includes the steps of:
(1) forming a first groove in the substrate 1 from the back surface 102 of the substrate 1 by using a suitable process such as photolithography and etching, wherein the first groove penetrates through the substrate 1 in a vertical direction;
(2) a first filling material is formed in the first trench by using chemical vapor deposition, physical vapor deposition or other suitable processes to obtain the deep trench isolation structure 14. The first filler material includes, but is not limited to, SiO2At least one of a high-K dielectric and a metal for reflecting light.
As an example, forming the back scattering structure 13 comprises the steps of:
(1) and forming a second trench in the substrate 1 from the back surface 102 of the substrate 1 by using a suitable process such as photolithography, etching, and the like, wherein the second trench is opened from the back surface 102 of the substrate 1 and extends toward the front surface 101 of the substrate 1, but does not reach the front surface 101 of the substrate 1. The second grooves can have different arrangements and shapes according to different requirements, for example, the horizontal cross section of the second grooves can be circular, cross-shaped, reversed-square and the like according to requirements, and the characteristic depth and the characteristic size of the second grooves can be 0-1 micron.
(2) A second filling material is formed in the second trench by using chemical vapor deposition, physical vapor deposition or other suitable processes to obtain the back scattering structure 13. The material of the second filling material includes but is not limited to Si3N4And SiO2One kind of (1).
Referring to fig. 10, a filter 15 is further formed on the back surface of the substrate 1, and a microlens 16 connected to the filter 15 is formed. Wherein, the incident light enters the substrate 1 through the micro lens 16 and the optical filter 15, and is received by the photodiode 2. The filter 15 may be a red filter, a blue filter or a green filter.
As an example, the substrate 17 may be subsequently removed or retained as desired.
In summary, the back-illuminated CMOS image sensor and the method for manufacturing the same according to the present invention use a Distributed Bragg Reflector (DBR) instead of a conventional metal reflector to achieve reflection of near-infrared light, and the DBR structure has the advantages of: (1) an insulating layer is originally required to be prepared between the front-section photodiode and the rear-section metal wiring, and relevant functions can be realized only by making the insulating layer into a DBR structure. (2) In the present invention, the DBR can adopt multilayer SiO2And Si3N4The periodic structure is compatible with the CMOS process, and the problems related to a metal reflector are avoided. In addition, by combining a Deep Trench Isolation (DTI) technology and a Back Scattering Technology (BST), the optical path of the near-infrared light can be further increased, the near-infrared light is effectively limited inside the PD, and the absorption enhancement of the near-infrared light is realized. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (21)
1. A backside-illuminated CMOS image sensor, comprising:
a substrate including a front surface and a back surface disposed opposite to each other;
a photodiode in the substrate;
the distributed Bragg reflector is positioned on the front surface of the substrate;
and the metal wiring layer is positioned on one surface of the distributed Bragg reflector, which is back to the substrate.
2. The backside-illuminated CMOS image sensor according to claim 1, wherein: the distributed Bragg reflector comprises at least one group of double-layer structures stacked in the vertical direction, the double-layer structures comprise a first insulating layer and a second insulating layer which are sequentially stacked in the vertical direction, and the refractive index of the first insulating layer is smaller than that of the second insulating layer.
3. The backside-illuminated CMOS image sensor according to claim 2, wherein: the first insulating layer comprises SiO2A layer of the second insulating layer comprising Si3N4Layer and TiO2One of the layers.
4. The backside-illuminated CMOS image sensor according to claim 1, wherein: the distributed Bragg reflector includes 2-100 sets of the double-layered structure stacked in a vertical direction.
5. The backside-illuminated CMOS image sensor according to claim 1, wherein: the backside illuminated CMOS image sensor further includes a deep trench isolation structure that penetrates the substrate in a vertical direction.
6. The backside-illuminated CMOS image sensor according to claim 5, wherein: the deep trench isolation structure is made of SiO2At least one of a high-K dielectric and a metal.
7. The backside-illuminated CMOS image sensor according to claim 1, wherein: the backside illuminated CMOS image sensor further comprises a backside scattering structure, wherein the backside scattering structure penetrates through the back side of the substrate in the vertical direction and extends towards the front side of the substrate.
8. The backside-illuminated CMOS image sensor according to claim 7, wherein: the refractive index of the back scattering structure is smaller than that of the substrate.
9. According to claimThe CMOS image sensor of claim 7, wherein: the back scattering structure is made of Si3N4And SiO2One kind of (1).
10. The CMOS image sensor of claim 7, wherein: the horizontal section of the back scattering structure is circular, cross-shaped or zigzag.
11. The CMOS image sensor of claim 7, wherein: the vertical projection of the back scattering structure on the horizontal plane is located in the area where the photodiode is located, and a preset distance is reserved between one end, facing the front surface of the substrate, of the back scattering structure and the photodiode.
12. The CMOS image sensor of claim 1, wherein: the back-illuminated CMOS image sensor further comprises an optical filter and a micro lens, wherein the optical filter is located on the back face of the substrate, and the micro lens is connected with the optical filter.
13. A method for manufacturing a CMOS image sensor is characterized by comprising the following steps:
providing a substrate, wherein the substrate comprises a front surface and a back surface which are oppositely arranged;
forming a photodiode in the substrate from a front side of the substrate;
forming a distributed Bragg reflector on the front surface of the substrate;
and forming a metal wiring layer on one surface of the distributed Bragg reflector, which is back to the substrate.
14. The method of manufacturing a CMOS image sensor according to claim 13, wherein: and alternately depositing a first insulating layer and a second insulating layer at least once on the front surface of the substrate to obtain the distributed Bragg reflector, wherein the refractive index of the first insulating layer is smaller than that of the second insulating layer.
15. The method of fabricating a CMOS image sensor according to claim 14, wherein: the first insulating layer comprises SiO2A layer of the second insulating layer comprising Si3N4Layer and TiO2One of the layers.
16. The method of manufacturing a CMOS image sensor according to claim 13, wherein: the method of forming the distributed bragg reflector includes a plasma enhanced chemical vapor deposition method.
17. The method of claim 13, further comprising the step of forming a deep trench isolation structure:
providing a substrate, and bonding the substrate and the metal wiring layer;
thinning the substrate from the back side of the substrate;
forming a first trench in the substrate from a backside of the substrate, the first trench penetrating the substrate in a vertical direction;
forming a first filling material in the first trench to obtain the deep trench isolation structure.
18. The method of claim 13, further comprising the step of forming a back scattering structure:
forming a second groove in the substrate from the back surface of the substrate, wherein the second groove is opened from the back surface of the substrate, extends towards the front surface of the substrate and does not reach the front surface of the substrate;
and forming a second filling material in the second groove to obtain the back scattering structure.
19. The method of fabricating a CMOS image sensor according to claim 18, wherein: the refractive index of the back scattering structure is smaller than that of the substrate.
20. The method of fabricating a CMOS image sensor according to claim 18, wherein: the vertical projection of the back scattering structure on the horizontal plane is located in the area where the photodiode is located, and a preset distance is reserved between one end, facing the front surface of the substrate, of the back scattering structure and the photodiode.
21. The method of fabricating a CMOS image sensor according to claim 13, further comprising the steps of:
forming an optical filter on the back of the substrate;
and forming a micro lens which is connected with the optical filter.
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