CN116469899A - Backside illuminated image sensor and preparation method thereof - Google Patents

Backside illuminated image sensor and preparation method thereof Download PDF

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Publication number
CN116469899A
CN116469899A CN202310396233.7A CN202310396233A CN116469899A CN 116469899 A CN116469899 A CN 116469899A CN 202310396233 A CN202310396233 A CN 202310396233A CN 116469899 A CN116469899 A CN 116469899A
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China
Prior art keywords
dielectric layer
semiconductor substrate
layer
isolation structure
back surface
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Chinese (zh)
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宋雷
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Shanghai Weijing Electronic Technology Co ltd
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Shanghai Weijing Electronic Technology Co ltd
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Priority to CN202310396233.7A priority Critical patent/CN116469899A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1464—Back illuminated imager structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1463—Pixel isolation structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Solid State Image Pick-Up Elements (AREA)
  • Element Separation (AREA)

Abstract

The invention discloses a back-illuminated image sensor and a preparation method thereof, wherein the method comprises the following steps: providing a semiconductor substrate, wherein the semiconductor substrate has a front surface and a back surface; forming a photosensitive unit on the front surface of the semiconductor substrate by ion implantation; forming a fourth dielectric layer on the front surface of the semiconductor substrate, and forming a transistor circuit and a metal interconnection layer in the fourth dielectric layer; etching the semiconductor substrate from the back surface of the semiconductor substrate until the fourth dielectric layer leaks out, so as to form a groove; forming a deep groove isolation structure in the groove, wherein the deep groove isolation structure comprises a first dielectric layer, an anti-reflection composite layer and a second dielectric layer which are sequentially stacked, and a cavity is formed in the second dielectric layer; a third dielectric layer is formed on the back surface of the semiconductor substrate, the third dielectric layer comprising a light blocking grid.

Description

Backside illuminated image sensor and preparation method thereof
Technical Field
The invention relates to the technical field of semiconductor integrated circuits, in particular to a back-illuminated image sensor and a preparation method thereof.
Background
An image sensor is a semiconductor device that converts an optical signal into an electrical signal. The conventional image sensor has a front-side incident structure, and a photosensitive unit is under a semiconductor substrate. Before entering the photosensitive cell, the incident light needs to pass through the metal interconnection layer and the dielectric layer, and this process causes light loss, thereby reducing quantum efficiency. In order to solve the problem, a back-illuminated structural image sensor is also provided at present, light is directly incident to the photosensitive unit without passing through the metal interconnection layer and the dielectric layer, and the incident light quantity is greatly improved. Particularly, in the case of smaller and smaller photosensitive units, the advantages of the back-illuminated structure are more remarkable.
In the image sensor with the back-illuminated structure, light is directly incident to the photosensitive unit without passing through the metal interconnection layer and the dielectric layer, so that the incident light quantity is greatly improved. Fig. 1 is a schematic cross-sectional view of a conventional backside illuminated image sensor, in which it can be seen that the thickness of the semiconductor substrate 100 is generally about 2um to 3um, and the deep trench isolation structure 20 cannot penetrate the entire semiconductor substrate 100 due to the limitation of the filling process, and the thickness of the deep trench isolation structure 20 is generally about 0.4um to 2um, so that there is inter-pixel crosstalk under the deep trench isolation structure 20. In addition, when the thickness of the semiconductor substrate 100 is further increased, the deep trench isolation structure 20 needs to be thickened simultaneously, and in order to ensure the filling effect, the filling material of the deep trench isolation structure 20 needs to be changed from tungsten metal to silicon oxide, and because the light blocking effect of the silicon oxide is relatively poor, a certain inter-pixel crosstalk exists in the deep trench isolation structure 20. Therefore, the image sensor with the standard back-illuminated structure has the problems of inter-pixel crosstalk under the deep trench isolation and inter-pixel crosstalk caused by the deep trench isolation.
Therefore, how to improve the inter-pixel crosstalk problem in the structure of the back-illuminated image sensor is a problem to be solved by those skilled in the art.
Disclosure of Invention
The embodiment of the invention provides a backside illuminated image sensor and a preparation method thereof, which can solve the problem of inter-pixel crosstalk existing below deep trench isolation and reduce inter-pixel crosstalk caused by the deep trench isolation.
In a first aspect, the present invention provides a method for preparing a backside illuminated image sensor, including: providing a semiconductor substrate, wherein the semiconductor substrate has a front surface and a back surface; forming a photosensitive unit on the front surface of the semiconductor substrate by ion implantation; forming a fourth dielectric layer on the front surface of the semiconductor substrate, and forming a transistor circuit and a metal interconnection layer in the fourth dielectric layer; etching the semiconductor substrate from the back surface of the semiconductor substrate until the fourth dielectric layer leaks out, so as to form a groove; forming a deep groove isolation structure in the groove, wherein the deep groove isolation structure comprises a first dielectric layer, an anti-reflection composite layer and a second dielectric layer which are sequentially stacked, and a cavity is formed in the second dielectric layer; and forming a third dielectric layer on the back surface of the semiconductor substrate, wherein the third dielectric layer comprises a light blocking grid.
Optionally, the first dielectric layer is a silicon oxide layer, and the second dielectric layer is a silicon oxide layer or a silicon nitride layer.
Optionally, the anti-reflection composite layer comprises an anti-reflection layer and a dielectric layer with high dielectric constant which are sequentially stacked, wherein the anti-reflection layer is arranged below the dielectric layer with high dielectric constant and is close to the back surface of the semiconductor substrate.
Optionally, the material of the light blocking grid is a metal or an insulating material with a light blocking effect.
Optionally, the material of the light blocking grid is tungsten, aluminum, silicon nitride or hafnium oxide.
In a second aspect, the present invention provides a backside illuminated image sensor comprising: the semiconductor substrate is provided with a front surface and a back surface, a photosensitive unit and a deep groove isolation structure, wherein the photosensitive unit and the deep groove isolation structure are positioned in the semiconductor substrate, the deep groove isolation structure comprises a first dielectric layer, an anti-reflection composite layer and a second dielectric layer which are sequentially stacked, and a cavity is formed in the third dielectric layer; and a third dielectric layer is further arranged on the semiconductor substrate, and a light blocking grid is arranged in the third dielectric layer.
Optionally, the anti-reflection composite layer comprises an anti-reflection layer and a dielectric layer with high dielectric constant which are sequentially stacked, wherein the anti-reflection layer is arranged below the dielectric layer with high dielectric constant and is close to the back surface of the semiconductor substrate.
The back-illuminated image sensor and the preparation method thereof provided by the invention have the beneficial effects that: through designing the deep trench isolation structure to penetrate through the whole semiconductor substrate, the inter-pixel crosstalk existing below the deep trench isolation structure 20 is thoroughly solved, the cavity in the deep trench isolation structure 20 can be formed through the reverse of weaker process filling capability, a reflection interface is formed, and the inter-pixel crosstalk existing in the deep trench isolation is further reduced. The invention can support thicker substrate silicon layer, namely, the thickness of the silicon layer is more than 3um, so the invention has simpler process realization and stronger crosstalk resistance compared with the standard Back SideIllumination, BSI CIS process, and can support larger thickness range of the silicon layer.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic cross-sectional view of a backside illuminated image sensor according to the prior art
FIG. 2 is a schematic cross-sectional view of a backside-illuminated image sensor according to an embodiment of the present invention;
fig. 3 is a schematic flow chart of a method for manufacturing a backside illuminated image sensor according to an embodiment of the present invention;
fig. 4A to fig. 4H are schematic cross-sectional views illustrating various intermediate process manufacturing stages of a backside illuminated image sensor according to an embodiment of the present invention.
Description of element numbers:
a 100 semiconductor substrate; a front surface of a semiconductor substrate 101; 102 a back surface of the semiconductor substrate;
10, a photosensitive unit; a 20 deep trench isolation structure;
200 a first dielectric layer; 300 antireflective composite layer; 400 a second dielectric layer; 500 light blocking grids;
600 a third dielectric layer; 700 a fourth dielectric layer; an 800 transistor circuit; 900 metal interconnect layers.
Detailed Description
In order to make the contents of the present invention more clear and understandable, the contents of the present invention will be further described with reference to the accompanying drawings. Of course, the invention is not limited to this particular embodiment, and common alternatives known to those skilled in the art are also encompassed within the scope of the invention.
In the following detailed description of the embodiments of the present invention, the structures of the present invention are not drawn to a general scale, and the structures in the drawings are partially enlarged, deformed, and simplified, so that the present invention should not be construed as being limited thereto.
According to the gist of the present invention, the present invention provides a schematic cross-sectional structure of a backside illuminated image sensor, as shown in fig. 2, comprising: the semiconductor substrate 100, the semiconductor substrate 100 has a front surface 101 and a back surface 102, a photosensitive cell 10, such as a Photo-Diode (PD), and a deep trench isolation structure 20 in the semiconductor substrate 100, the deep trench isolation structure 20 including a first dielectric layer 200, an anti-reflection composite layer 300, and a second dielectric layer 400 stacked in this order, wherein the second dielectric layer is provided with a cavity. A third dielectric layer 600 is further provided on the semiconductor substrate 100, and a light blocking grid 500 is provided in the third dielectric layer 600. Wherein the Anti-reflective composite layer 300 may include an Anti-reflective layer (AR) and a high-k dielectric layer (HK) stacked in sequence, wherein the AR layer is disposed under the HK layer and adjacent to the back surface 102 of the semiconductor substrate 100.
Alternatively, the material of the light blocking grid 500 is a metal or an insulating material having a light blocking effect such as tungsten (W), aluminum (Al), silicon nitride (SiN), or hafnium oxide (HfO).
In addition, the backside illuminated image sensor may further include a fourth dielectric layer 700 on the front surface 101 of the semiconductor substrate 100, and a plurality of transistor circuits 800 and metal interconnection layers 900 in the fourth dielectric layer 700. The transistor circuit 800 is used for signal transmission and processing.
As can be seen from the above structure, the deep trench isolation structure in the back-illuminated structure of the present invention passes through the entire semiconductor substrate, and thoroughly solves the inter-pixel crosstalk existing under the deep trench isolation structure 20. By forming the reflective interface through the cavity structure in the deep trench isolation structure 20, inter-pixel crosstalk existing in the deep trench isolation itself is further reduced.
The structure of the invention can be used in various back-illuminated image sensors requiring storage capacitors such as 4T, 5T, 6T, 8T or 12T.
For the purpose of making the objects, technical solutions and advantages of the present invention more clear, the following further illustrates a schematic flow chart of a method for manufacturing a backside illuminated image sensor in conjunction with fig. 3, and fig. 4A to fig. 4H illustrate schematic step results of each process manufacturing stage in this example, respectively.
Referring to fig. 3, the preparation process of the backside illuminated image sensor provided by the embodiment of the invention includes the following steps:
s301, a semiconductor substrate 100 is provided, the semiconductor substrate having a front surface 101 and a back surface 102.
As shown in fig. 4A, the semiconductor substrate 100 may be an N-type or P-type semiconductor substrate. The material of the semiconductor substrate 100 includes one or more of silicon, germanium, silicon carbide, gallium arsenide, and indium gallium, and the semiconductor substrate 100 may be a silicon semiconductor substrate on an insulator or a germanium semiconductor substrate on an insulator.
S302, the photosensitive cell 10 is formed on the front surface 101 of the semiconductor substrate 100 by ion implantation.
Illustratively, as shown in fig. 4B, a plurality of photosensitive cells 10 are fabricated by ion implantation on the front surface 101 of the semiconductor substrate 100, and are formed by patterning and dielectric deposition.
S303, forming a fourth dielectric layer 700 on the front surface 101 of the semiconductor substrate 100, a transistor circuit 800 and a metal interconnection layer 900 in the fourth dielectric layer 700.
In this step, as shown in fig. 4C, specifically, a communication hole may be formed by depositing, patterning and photolithography, and etching the fourth dielectric layer 700; then, metal deposition, patterning lithography, and etching are performed to form the metal interconnect layer 900. And, in this embodiment, the transistor circuit 800 is implemented by deposition and patterned etching of polysilicon, and the transistor circuit 800 is used to implement a circuit for signal transmission and processing.
And S304, etching the semiconductor substrate from the back surface 102 of the semiconductor substrate until the fourth dielectric layer 700 leaks out, so as to form a groove.
Illustratively, as shown in fig. 4D, the present embodiment performs photolithography on the semiconductor substrate 100, and etches through the entire semiconductor substrate 100 until the fourth dielectric layer 700 leaks out.
S305, forming a deep trench isolation structure 20 in the trench, where the deep trench isolation structure 20 includes a first dielectric layer 200, an anti-reflection composite layer 300, and a second dielectric layer 400 that are sequentially stacked, and a cavity is disposed in the second dielectric layer.
Exemplary, as shown in FIG. 4E, after forming the trench, a first dielectric layer, such as a layer of about 20A of SiO, is grown over the trench 2 A layer. Thereafter, as shown in fig. 4F, an anti-reflection composite layer 300 is grown on the first dielectric layer, wherein the anti-reflection composite layer 300 may include an AR layer and an HK layer, and the material is generally AlO, hfO, taO, and the thickness is about 100-500A. Then, as shown in FIG. 4G, a second dielectric layer 400 is formed on the anti-reflection composite layer 300, wherein the second dielectric layer 400 is SiO 2 Insulating materials such as SiN, and the like, the filling capability is reduced by filling adjustment, and a cavity is formed in the second dielectric layer 400, and then the surface can be polished by Chemical Mechanical Polishing (CMP) to form a structure as shown in fig. 4H.
S306, a third dielectric layer 600 is formed on the back surface of the semiconductor substrate 100, the third dielectric layer 600 including the light blocking grid 500.
In this step, the BSI CIS structure may be further completed by a standard BSI CIS process after the deep trench isolation structure 20 is formed, and the light blocking grid 500 may be formed by filling a metal or insulating material having a light blocking effect such as tungsten (W), aluminum (Al), silicon nitride (SiN), or hafnium oxide (HfO), as shown in fig. 2.
In summary, the present invention thoroughly solves the inter-pixel crosstalk existing under the deep trench isolation structure 20 by designing the deep trench isolation structure to penetrate through the whole semiconductor substrate, and forms the cavity in the deep trench isolation structure 20 by the weaker process filling capability reaction to form the reflective interface, thereby further reducing the inter-pixel crosstalk existing in the deep trench isolation. The invention can support thicker substrate silicon layer, namely, the thickness of the silicon layer is more than 3um, so the invention has simpler process realization and stronger crosstalk resistance compared with the standard BSI CIS process, and can support larger thickness range of the silicon layer.
The foregoing description is only of the preferred embodiments of the present invention, and the embodiments are not intended to limit the scope of the invention, so that all changes made in the equivalent structures of the present invention described in the specification and the drawings are included in the scope of the invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention.
Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. A method for manufacturing a backside illuminated image sensor, comprising:
providing a semiconductor substrate, wherein the semiconductor substrate has a front surface and a back surface;
forming a photosensitive unit on the front surface of the semiconductor substrate by ion implantation;
forming a fourth dielectric layer on the front surface of the semiconductor substrate, and forming a transistor circuit and a metal interconnection layer in the fourth dielectric layer;
etching the semiconductor substrate from the back surface of the semiconductor substrate until the fourth dielectric layer leaks out, so as to form a groove;
forming a deep groove isolation structure in the groove, wherein the deep groove isolation structure comprises a first dielectric layer, an anti-reflection composite layer and a second dielectric layer which are sequentially stacked, and a cavity is formed in the second dielectric layer;
and forming a third dielectric layer on the back surface of the semiconductor substrate, wherein the third dielectric layer comprises a light blocking grid.
2. The method of claim 1, wherein the first dielectric layer is a silicon oxide layer and the second dielectric layer is a silicon oxide layer or a silicon nitride layer.
3. The method of claim 1, wherein the antireflective composite layer comprises an antireflective layer and a high dielectric constant dielectric layer that are sequentially stacked, wherein the antireflective layer is disposed below the high dielectric constant dielectric layer and adjacent to a back surface of the semiconductor substrate.
4. A method according to any one of claims 1 to 3, characterized in that the material of the light-blocking grid is a metal or an insulating material having a light-blocking effect.
5. The method of claim 4, wherein the material of the light blocking grid is tungsten, aluminum, silicon nitride, or hafnium oxide.
6. A backside illuminated image sensor, comprising: the semiconductor substrate is provided with a front surface and a back surface, a photosensitive unit and a deep groove isolation structure, wherein the photosensitive unit and the deep groove isolation structure are positioned in the semiconductor substrate, the deep groove isolation structure comprises a first dielectric layer, an anti-reflection composite layer and a second dielectric layer which are sequentially stacked, and a cavity is formed in the second dielectric layer; and a third dielectric layer is further arranged on the semiconductor substrate, and a light blocking grid is arranged in the third dielectric layer.
7. The back-illuminated image sensor of claim 6, wherein the anti-reflection composite layer comprises an anti-reflection layer and a high-k dielectric layer stacked in sequence, wherein the anti-reflection layer is disposed below the high-k dielectric layer and adjacent to a back surface of the semiconductor substrate.
CN202310396233.7A 2023-04-12 2023-04-12 Backside illuminated image sensor and preparation method thereof Pending CN116469899A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310396233.7A CN116469899A (en) 2023-04-12 2023-04-12 Backside illuminated image sensor and preparation method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310396233.7A CN116469899A (en) 2023-04-12 2023-04-12 Backside illuminated image sensor and preparation method thereof

Publications (1)

Publication Number Publication Date
CN116469899A true CN116469899A (en) 2023-07-21

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