CN115000113A - Backside illuminated image sensor and manufacturing method thereof - Google Patents
Backside illuminated image sensor and manufacturing method thereof Download PDFInfo
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- CN115000113A CN115000113A CN202210745442.3A CN202210745442A CN115000113A CN 115000113 A CN115000113 A CN 115000113A CN 202210745442 A CN202210745442 A CN 202210745442A CN 115000113 A CN115000113 A CN 115000113A
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- 229920002120 photoresistant polymer Polymers 0.000 claims description 90
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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
- H01L27/14636—Interconnect structures
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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
- H01L27/1463—Pixel isolation structures
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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
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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
- H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
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Abstract
The invention provides a back-illuminated image sensor and a manufacturing method thereof, which improve the light blocking performance of a metal grid by forming a connected structure of a deep groove isolation structure and the metal grid, further improve the optical crosstalk problem of the back-illuminated image sensor and improve the performance of the back-illuminated image sensor. Meanwhile, the metal grating is connected with the metal bonding pad through the grating bonding pad connecting layer, the connected metal bonding pad can be freely selected and can be a grounded metal bonding pad or a metal bonding pad connected with electric potential, so that the electric potential of the metal grating can be adjusted, and the performance of the back-illuminated image sensor is further improved.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a back-illuminated image sensor and a manufacturing method thereof.
Background
There is a degree of electronic and optical crosstalk between pixels of a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Electronic crosstalk refers to diffusion or scattering of electrons to other pixels, and optical crosstalk is mainly caused by light incident on adjacent pixels. In view of optical crosstalk, the conventional back-illuminated image sensor technology usually adopts the addition of deep isolation trenches and metal grids for improvement.
In the conventional back-illuminated image sensor, tungsten is usually filled in a deep isolation trench to form a deep trench isolation structure, an oxide layer is deposited to cover the deep trench isolation structure, and an aluminum layer is deposited to etch to form a metal grid.
Disclosure of Invention
The invention aims to provide a back-illuminated image sensor and a manufacturing method thereof, which can improve the light blocking performance of a metal grating, further improve the optical crosstalk problem of the back-illuminated image sensor and improve the performance of the back-illuminated image sensor.
In order to solve the above technical problem, the present invention provides a method for manufacturing a backside illuminated image sensor, comprising the following steps:
providing a substrate, wherein the substrate comprises a pixel area and a non-pixel area, and a plurality of pixel electrodes positioned in the pixel area and a plurality of metal interconnection layers positioned in the non-pixel area are formed in the substrate;
forming a plurality of deep isolation trenches in a pixel region of the substrate, and forming a plurality of first openings in a non-pixel region of the substrate, wherein the deep isolation trenches are located above the pixel electrodes, and the first openings are located above the metal interconnection layer;
forming a second opening at the bottom of the first opening, wherein the second opening exposes a part of the metal interconnection layer;
sequentially forming a first metal material layer and a second metal material layer, wherein the first metal material layer fills the deep isolation trench and the second opening, fills the side wall and the bottom of the first opening and covers the substrate, and the second metal material layer covers the first metal material layer;
etching the second metal material layer, and forming a metal pad in the first opening; and
etching the first metal material layer, forming a deep trench isolation structure and a metal grid which is positioned above the deep trench isolation structure and connected with the deep trench isolation structure in the pixel region, reserving the first metal material layer in the non-pixel region as a grid pad connection layer, connecting the metal grid close to the non-pixel region with the metal pad through the grid pad connection layer, and connecting the metal pad with the metal interconnection layer through the grid pad connection layer.
Optionally, the method of forming a plurality of deep isolation trenches in the pixel region of the substrate and forming a plurality of first openings in the non-pixel region of the substrate includes:
forming a first photoresist layer on the substrate, and patterning the first photoresist layer to form a patterned first photoresist layer;
etching part of the substrate by taking the patterned first photoresist layer as a mask, and forming a plurality of first openings in the non-pixel region, wherein each first opening is positioned above each metal interconnection layer;
removing the patterned first photoresist layer;
forming a second photoresist layer covering the substrate and filling the first opening; patterning the second photoresist layer to form a patterned second photoresist layer;
etching part of the substrate by taking the patterned second photoresist layer as a mask, and forming a plurality of deep isolation grooves in the pixel region, wherein each deep isolation groove is positioned above each pixel electrode; and
and removing the patterned second photoresist layer.
Optionally, after forming the first opening and the deep isolation trench, before forming the second opening, the manufacturing method further includes:
forming a dielectric layer covering the first opening and the side walls and the bottom of the deep isolation trench and covering the substrate; and
forming a protective layer on the dielectric layer, wherein the protective layer covers the first opening and the side wall and the bottom of the deep isolation groove.
Optionally, the method for etching the second metal material layer and forming a metal pad in the first opening includes:
forming a third photoresist layer on the second metal material layer, and patterning the third photoresist layer to form a patterned third photoresist layer, wherein the patterned third photoresist layer exposes a part of the second metal material layer in the first opening; and
and etching the second metal material layer by taking the patterned third photoresist layer as a mask to form the metal pad, wherein a space is formed between the side wall of the metal pad and the first metal material layer on the side wall of the first opening.
Optionally, after etching the second metal material layer and before etching the first metal material layer, the method further includes:
and forming a hard mask layer, wherein the hard mask layer covers the first metal material layer and the metal bonding pad.
Optionally, the method for forming the deep trench isolation structure and the metal grid includes:
forming a fourth photoresist layer on the hard mask layer, and patterning the fourth photoresist layer to form a patterned fourth photoresist layer, wherein the patterned fourth photoresist layer exposes a region between adjacent shallow isolation trenches;
etching the hard mask layer by taking the patterned fourth photoresist layer as a mask to form a patterned hard mask layer;
removing the patterned fourth photoresist layer; and
and etching the first metal material layer by taking the patterned hard mask layer as a mask until the protective layer is exposed so as to form a deep trench isolation structure and a metal grid which is positioned on the deep trench isolation structure and connected with the deep trench isolation structure in the pixel region.
Optionally, after forming the deep trench isolation structure and the metal grid, the method further includes:
forming a fifth photoresist layer, wherein the fifth photoresist layer covers the patterned hard mask layer and the exposed protective layer;
patterning the fifth photoresist layer to form a patterned fifth photoresist layer, wherein the patterned fifth photoresist layer exposes the region where the metal pad is located;
etching the patterned hard mask layer by taking the patterned fifth photoresist layer as a mask to expose the metal bonding pad; and
and removing the patterned fifth photoresist layer.
Optionally, the material of the first metal material layer includes tungsten, the material of the second metal material layer includes aluminum, the material of the dielectric layer includes a high dielectric constant material, the material of the protective layer includes silicon oxide, and the material of the hard mask layer includes silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof.
Optionally, after the deep isolation trench structure, the metal grid, and the grid pad connection layer are formed, the manufacturing method further includes: and forming a color filter film in the pixel region, wherein the color filter film is positioned between the metal grids and covers the metal grids.
Correspondingly, the invention also provides a back-illuminated image sensor which is manufactured by adopting the manufacturing method of the back-illuminated image sensor.
In the back-illuminated image sensor and the manufacturing method thereof provided by the invention, the integral structure of the deep groove isolation structure connected with the metal grating is formed, so that the light blocking performance of the metal grating is improved, the optical crosstalk problem of the back-illuminated image sensor is further improved, and the performance of the back-illuminated image sensor is improved. Meanwhile, the metal grating is connected with the metal bonding pad through the grating bonding pad connecting layer, the connected metal bonding pad can be freely selected and can be a grounded metal bonding pad or a metal bonding pad connected with electric potential, so that the electric potential of the metal grating can be adjusted, and the performance of the back-illuminated image sensor is further improved.
Further, tungsten is adopted as the metal grid, and compared with the prior art that aluminum is adopted as the metal grid, the light blocking performance of the metal grid is further improved, so that the performance of the back-illuminated image sensor is further improved.
Drawings
It will be appreciated by those skilled in the art that the drawings are provided for a better understanding of the invention and do not constitute any limitation to the scope of the invention.
Fig. 1 is a flowchart illustrating a method for manufacturing a backside illuminated image sensor according to an embodiment of the present invention.
Fig. 2 to fig. 11 are schematic structural diagrams of steps of a method for manufacturing a back-illuminated image sensor according to an embodiment of the invention.
Fig. 12 is a top view of a back-illuminated image sensor according to an embodiment of the invention.
Reference numerals:
100-a substrate; 101-pixel electrodes; 102-metal interconnect layer; 103-a first opening; 104-deep isolation trenches; 105-a dielectric layer; 106-protective layer; 107-second opening; 108-a first metallic material layer; 109-a second metallic material layer; 110-metal pads; 111-hard mask layer; 112-deep trench isolation structures; 113-a metal grid; 114-a patterned hard mask layer; 115-a third opening; 116-a grid pad connection layer; 117-color filter.
Detailed Description
To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be noted that the drawings are in simplified form and are not to scale, but are provided for the purpose of facilitating and clearly illustrating embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings are intended to show different emphasis, sometimes in different proportions.
As used in this disclosure, the singular forms "a," "an," and "the" include plural referents, the term "or" is generally employed in a sense including "and/or," the terms "a," "an," and "the" are generally employed in a sense including "at least one," the terms "at least two" are generally employed in a sense including "two or more," and further, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to imply that the number of indicated technical features is essential. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or at least two of the feature unless the content clearly dictates otherwise.
Fig. 1 is a flowchart illustrating a method for manufacturing a backside illuminated image sensor according to an embodiment of the present invention.
As shown in fig. 1, the method for manufacturing the back-illuminated image sensor includes the following steps:
s1: providing a substrate, wherein the substrate comprises a pixel area and a non-pixel area, and a plurality of pixel electrodes positioned in the pixel area and a plurality of metal interconnection layers positioned in the non-pixel area are formed in the substrate;
s2: forming a plurality of deep isolation trenches in a pixel region of the substrate, and forming a plurality of first openings in a non-pixel region of the substrate, wherein the deep isolation trenches are located above the pixel electrodes, and the first openings are located above the metal interconnection layers;
s3: forming a second opening at the bottom of the first opening, wherein the second opening exposes a part of the metal interconnection layer;
s4: sequentially forming a first metal material layer and a second metal material layer, wherein the first metal material layer fills the deep isolation trench and the second opening, fills the side wall and the bottom of the first opening and covers the substrate, and the second metal material layer covers the first metal material layer;
s5: etching the second metal material layer, and forming a metal pad in the first opening;
s6: etching the first metal material layer, forming a deep trench isolation structure and a metal grid which is positioned above the deep trench isolation structure and connected with the deep trench isolation structure in the pixel region, reserving the first metal material layer of the non-pixel region as a grid pad connection layer, connecting the metal grid close to the non-pixel region with the metal pad through the grid pad connection layer, and connecting the metal pad with the metal interconnection layer through the grid pad connection layer.
Fig. 2 to 11 are schematic structural diagrams of steps of a method for manufacturing a back-illuminated image sensor according to an embodiment of the present invention, and fig. 12 is a top view of the back-illuminated image sensor according to an embodiment of the present invention. Next, a method for manufacturing a backside illuminated image sensor according to an embodiment of the present invention will be described in detail with reference to fig. 1 and fig. 2 to 12.
In step S1, please refer to fig. 2, a substrate 100 is provided, the substrate 100 includes a pixel area a and a non-pixel area B, and a plurality of pixel electrodes 101 located in the pixel area a and a plurality of metal interconnection layers 102 located in the non-pixel area B are formed in the substrate 100.
The substrate 100 may be made of silicon, germanium, silicon carbide, gallium arsenide, indium gallium arsenide, or the like, or may be made of silicon on insulator or germanium on insulator; or may be other materials such as group III-V compounds such as gallium arsenide. In this embodiment, the material of the substrate 100 is preferably silicon.
The substrate 100 includes a pixel region a and a non-pixel region B surrounding the pixel region a (see fig. 12). A plurality of pixel electrodes 101 and a plurality of metal interconnection layers 102 are formed in the substrate 100, the pixel electrodes 101 are located in the pixel region a, the metal interconnection layers 102 are located in the non-pixel region B, and only one metal interconnection layer 102 is shown in fig. 2 to 11. The pixel electrode 101 and the metal interconnection layer 102 may be formed by a manufacturing method known to those skilled in the art, which is not described in detail herein.
In step S2, please refer to fig. 3, a plurality of deep isolation trenches 104 are formed in the pixel region a of the substrate 100, a plurality of first openings 103 are formed in the non-pixel region B of the substrate 100, the deep isolation trenches 104 are located above the pixel electrode 101, and the first openings 103 are located above the metal interconnection layer 102.
Specifically, a plurality of first openings 103 are first formed in the non-pixel region B of the substrate 100. Referring to fig. 2, the first opening 103 is formed in the non-pixel region B of the substrate 100. Illustratively, first, a first photoresist layer (not shown) is formed on the substrate 100, and the first photoresist layer is patterned, for example, the first photoresist layer is exposed and developed to form a patterned first photoresist layer, and the patterned first photoresist layer exposes the area where the first opening 103 is to be formed. Then, using the patterned first photoresist layer as a mask, etching a portion of the substrate 100, and forming a plurality of first openings 103 in the non-pixel region B, where each first opening 103 is located above each metal interconnection layer 102, that is, the first openings 103 correspond to the metal interconnection layers 102 one to one. And finally, removing the patterned first photoresist layer.
A plurality of deep isolation trenches 104 are then formed within the pixel region a of the substrate 100. Referring to fig. 3, first, a second photoresist layer (not shown) is formed, the second photoresist layer covers the substrate 100 and fills the first opening 103, the second photoresist layer is patterned, for example, the second photoresist layer is exposed and developed to form a patterned second photoresist layer, and the patterned second photoresist layer exposes a region where the deep isolation trench 104 is to be formed. Then, using the patterned second photoresist layer as a mask, etching a part of the substrate 100, and forming a plurality of deep isolation trenches 104 in the pixel region a, where each deep isolation trench 104 is located above each pixel electrode 101, that is, the deep isolation trenches 104 correspond to the pixel electrodes 101 one to one. And finally, removing the patterned second photoresist layer.
In this embodiment, the first opening 103 is formed first, and then the deep isolation trench 104 is formed. In other embodiments, the deep isolation trench 104 may be formed first, and then the first opening 103 is formed, or the first opening 103 and the deep isolation trench 104 may be formed in other manners, which is not limited in the present invention.
Next, referring to fig. 4, a dielectric layer 105 is formed, wherein the dielectric layer 105 covers the sidewalls and the bottom of the first opening 103 and the deep isolation trench 104, and covers the substrate 100. In the present embodiment, the material of the dielectric layer 105 includes a high dielectric constant material, such as hafnium oxide, aluminum oxide, or tantalum oxide, and the dielectric layer 105 can be formed by Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), thermal oxidation, electroplating, electroless plating, or a combination thereof.
Then, a protection layer 106 is formed on the dielectric layer 105, the protection layer 106 covers the dielectric layer 105, and the protection layer 106 only covers the first opening 103 and the sidewall and the bottom of the isolation trench 104. In this embodiment, the material of the protection layer 106 includes silicon oxide, and the protection layer 106 may be formed by chemical vapor deposition, physical vapor deposition, or the like.
In step S3, please refer to fig. 5, a second opening 107 is formed at the bottom of the first opening 103, and the second opening 107 exposes a portion of the metal interconnection layer 102.
Specifically, a mask layer (e.g., a photoresist layer) may be formed on the protection layer 106, and the mask layer is patterned to expose a region of the protection layer 106 where the second opening is to be formed. Then, the protective layer 106, the dielectric layer 105 and the substrate 100 are sequentially etched by using the patterned mask layer as a mask until the metal interconnection layer 102 is exposed. And finally, removing the patterned mask layer.
The second opening 107 is located at the bottom of the first opening 103, and the cross-sectional width of the second opening 107 is much smaller than the cross-sectional width of the first opening 103.
In step S4, referring to fig. 6, a first metal material layer 108 and a second metal material layer 109 are formed, wherein the first metal material layer 108 fills the deep isolation trench 104 and the second opening 107, fills the sidewall and the bottom of the first opening 103, and covers the substrate 100, and the second metal material layer 109 covers the first metal material layer 108.
The material of the first metal material layer 108 includes tungsten, the material of the second metal material layer 109 includes aluminum, and the first metal material layer 108 and the second metal material layer 109 may be formed by chemical vapor deposition, physical vapor deposition, or the like.
In step S5, referring to fig. 7, the second metal material layer 109 is etched, and a metal pad 110 is formed in the first opening 103.
Specifically, a third photoresist layer (not shown) is formed on the second metal material layer 109, and the third photoresist layer is patterned to form a patterned third photoresist layer, wherein the patterned third photoresist layer exposes a portion of the second metal layer in the first opening 103. Then, the second metal material layer 109 is etched by using the patterned third photoresist layer as a mask to form the metal pad 110, and a space is formed between the sidewall of the metal pad 110 and the first metal material layer 108 on the sidewall of the first opening 103, that is, only the bottom of the metal pad 110 is connected to the first metal material layer 108.
Next, referring to fig. 8, a hard mask layer 111 is formed, where the hard mask layer 111 covers the first metal material layer 108 and the metal pad 110, and the hard mask layer 111 also fills a gap between the sidewall of the metal pad 110 and the first metal material layer 108. In this embodiment, the hard mask layer 111 includes silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof, and the hard mask layer 111 may be a single layer or a multi-layer.
In step S6, please refer to fig. 11, the first metal material layer 108 is etched, a deep trench isolation structure 112 and a metal grid 113 located above the deep trench isolation structure 112 and connected to the deep trench isolation structure 112 are formed in the pixel region a, the first metal material layer 108 of the non-pixel region B is reserved as a grid pad connection layer 116, the metal grid 113 near the non-pixel region B is connected to the metal pad 110 through the grid pad connection layer 116, and the metal pad 110 is connected to the metal interconnect layer 102 through the grid pad connection layer 116.
Specifically, referring to fig. 9, first, a fourth photoresist layer (not shown) is formed on the hard mask layer 111, and the fourth photoresist layer is patterned to form a patterned photoresist layer, where the patterned fourth photoresist layer exposes a region between adjacent shallow isolation trenches 104; etching the hard mask layer 110 by using the patterned fourth photoresist layer as a mask to form a patterned hard mask layer 114; then, removing the patterned fourth photoresist layer; then, the patterned hard mask layer 114 is used as a mask to etch the first metal material layer 108 until the protection layer 106 is exposed, so as to form a deep trench isolation structure 112 and a metal grid 113 located above the deep trench isolation structure 112 and connected to the deep trench isolation structure 112 in the pixel region a.
Next, referring to fig. 10, a fifth photoresist layer (not shown) is formed, wherein the fifth photoresist layer covers the patterned hard mask layer 114 and the exposed protective layer 106; patterning the fifth photoresist layer to form a patterned fifth photoresist layer, wherein the patterned fifth photoresist layer exposes the region where the metal pad 110 is located; etching the patterned hard mask layer 114 by using the patterned fifth photoresist layer as a mask to form a third opening 115, wherein the metal pad 110 is exposed out of the third opening 115; and finally, removing the patterned fifth photoresist layer.
The first metal material layer 108 is filled in the deep isolation trench 104 and covers the deep isolation trench 104, forming a deep trench isolation structure 112 and a metal grid 113 located above the deep trench isolation structure 112 and connected to the deep trench isolation structure 112. The invention forms the integral structure of the deep groove isolation structure 112 and the metal grid 113, improves the light blocking performance of the metal grid 113, further improves the optical crosstalk problem of the back-illuminated image sensor, and improves the performance of the back-illuminated image sensor. Further, the material of the first metal material layer 108 includes tungsten, and the metal grating 113 and the deep trench isolation structure 112 are made of tungsten, which further improves the light blocking performance of the metal grating 113 compared to the prior art that aluminum is used as a metal grating, thereby further improving the performance of the back-illuminated image sensor.
In step S6, only a portion of the hard mask layer 111 and the first metal material layer 108 in the pixel region B and a portion of the patterned hard mask layer 114 in the non-pixel region B are etched, the first metal material layer 108 in the remaining region is retained as a grid pad connection layer 116, the metal grid 113 near the non-pixel region B is connected to the metal pad 110 through the grid pad connection layer 116, and the metal pad 110 is connected to the metal interconnection layer 102 through the grid pad connection layer 116.
Next, referring to fig. 11, a color filter 117 is formed in the pixel region a, wherein the color filter 117 is located between the metal grids 113 and covers the metal grids 113. The color filter 117 can effectively improve the light blocking performance of the metal grid 113, thereby further improving the performance of the back-illuminated image sensor.
Referring to fig. 12, a plurality of metal pads 110 are formed in the non-pixel region B, and the metal grid 113 may be connected to one or more of the metal pads 110 through a grid pad connection layer 116. The metal pad 110 connected to the metal grid 113 may be grounded or may be connected to a potential, so that the metal grid 113 may be potential-adjusted, thereby improving the performance of the back-illuminated image sensor.
In the back side illumination image sensor and the manufacturing method thereof provided by the invention, a substrate 100 comprises a pixel area A and a non-pixel area B, and a plurality of pixel electrodes 101 positioned in the pixel area A and a plurality of metal interconnection layers 102 positioned in the non-pixel area B are formed in the substrate 100; forming a plurality of deep isolation trenches 104 in the pixel region a of the substrate 100, and forming a plurality of first openings 103 in the non-pixel region B of the substrate 100, wherein the deep isolation trenches 104 are located above the pixel electrodes 101, and the first openings 103 are located above the metal interconnection layers 102; forming a second opening 107 at the bottom of the first opening 103, wherein the second opening 107 exposes a portion of the metal interconnection layer 102; sequentially forming a first metal material layer 108 and a second metal material layer 109, wherein the first metal material layer 108 fills the deep isolation trench 104 and the second opening 107, fills the sidewall and the bottom of the first opening 103, and covers the substrate 100, and the second metal material layer 109 covers the first metal material layer 108; etching the second metal material layer 109 to form a metal pad 110 in the first opening 103; etching the first metal material layer 108, forming a deep trench isolation structure 112 and a metal grid 113 located above the deep trench isolation structure 112 and connected to the deep trench isolation structure 112 in the pixel region B, reserving the first metal material layer 108 in the non-pixel region B as a grid pad connection layer 116, connecting the metal grid 113 near the non-pixel region B to the metal pad 110 through the grid pad connection layer 116, and connecting the metal pad 110 to the metal interconnection layer 102 through the grid pad connection layer 116.
The invention forms a connected structure of the deep trench isolation structure 112 and the metal grid 113, improves the light blocking performance of the metal grid 113, further improves the optical crosstalk problem of the back-illuminated image sensor, and improves the performance of the back-illuminated image sensor.
Meanwhile, the metal grid 113 and the metal pad 110 are connected through the grid pad connection layer 116, the metal pad 110 connected can be freely selected, and can be the grounded metal pad 110 or the metal pad 110 connected with the potential, so that the potential of the metal grid 113 can be adjusted, and the performance of the back-illuminated image sensor is further improved.
Further, by using tungsten as the metal grid 113, compared with the prior art in which aluminum is used as the metal grid, the light blocking performance of the metal grid 113 is further improved, thereby further improving the performance of the back-illuminated image sensor.
Correspondingly, the invention also provides a back-illuminated image sensor which is manufactured by adopting the manufacturing method of the back-illuminated image sensor. Referring to fig. 11 and 12, the backside illuminated image sensor includes:
a substrate 100, wherein the substrate 100 comprises a pixel area A and a non-pixel area B, and a plurality of pixel electrodes 101 located in the pixel area A and a plurality of metal interconnection layers 102 located in the non-pixel area B are formed in the substrate 100;
a deep trench isolation structure 112 located within the substrate 100 of the pixel region A, the deep trench isolation structure 112 located above the pixel electrode 101;
a metal grid 113 located on the substrate 100 of the pixel region a, wherein the metal grid 113 is located above the deep trench isolation structure 112 and connected to the deep trench isolation structure 112;
a metal pad 110 located in the substrate 100 in the non-pixel region B, wherein the metal pad 110 is located above the metal interconnection layer 102, the metal pad 110 is connected to the metal interconnection layer 102 through the grid pad connection layer 116, and the metal grid 113 close to the non-pixel region B is connected to the metal pad 110 through the grid pad connection layer 116.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A method for manufacturing a back-illuminated image sensor is characterized by comprising the following steps:
providing a substrate, wherein the substrate comprises a pixel area and a non-pixel area, and a plurality of pixel electrodes positioned in the pixel area and a plurality of metal interconnection layers positioned in the non-pixel area are formed in the substrate;
forming a plurality of deep isolation trenches in a pixel region of the substrate, and forming a plurality of first openings in a non-pixel region of the substrate, wherein the deep isolation trenches are located above the pixel electrodes, and the first openings are located above the metal interconnection layers;
forming a second opening at the bottom of the first opening, wherein the second opening exposes a part of the metal interconnection layer;
sequentially forming a first metal material layer and a second metal material layer, wherein the first metal material layer fills the deep isolation trench and the second opening, fills the side wall and the bottom of the first opening and covers the substrate, and the second metal material layer covers the first metal material layer;
etching the second metal material layer, and forming a metal bonding pad in the first opening; and
etching the first metal material layer, forming a deep trench isolation structure and a metal grid which is positioned above the deep trench isolation structure and connected with the deep trench isolation structure in the pixel region, reserving the first metal material layer in the non-pixel region as a grid pad connecting layer, connecting the metal grid close to the non-pixel region with the metal pad through the grid pad connecting layer, and connecting the metal pad with the metal interconnection layer through the grid pad connecting layer.
2. The method of claim 1, wherein forming a plurality of deep isolation trenches in a pixel region of the substrate, and forming a plurality of first openings in a non-pixel region of the substrate comprises:
forming a first photoresist layer on the substrate, and patterning the first photoresist layer to form a patterned first photoresist layer;
etching part of the substrate by taking the patterned first photoresist layer as a mask, and forming a plurality of first openings in the non-pixel region, wherein each first opening is positioned above each metal interconnection layer;
removing the patterned first photoresist layer;
forming a second photoresist layer covering the substrate and filling the first opening; patterning the second photoresist layer to form a patterned second photoresist layer;
etching part of the substrate by taking the patterned second photoresist layer as a mask, and forming a plurality of deep isolation grooves in the pixel region, wherein each deep isolation groove is positioned above each pixel electrode; and
and removing the patterned second photoresist layer.
3. The method of fabricating a back-illuminated image sensor as in claim 1, wherein after forming the first opening and the deep isolation trench, and before forming the second opening, the method further comprises:
forming a dielectric layer covering the first opening and the side walls and the bottom of the deep isolation trench and covering the substrate; and
forming a protective layer on the dielectric layer, wherein the protective layer covers the first opening and the side wall and the bottom of the deep isolation groove.
4. The method of fabricating a backside illuminated image sensor as claimed in claim 3, wherein the method of etching the second metal material layer and forming a metal pad in the first opening comprises:
forming a third photoresist layer on the second metal material layer, and patterning the third photoresist layer to form a patterned third photoresist layer, wherein the patterned third photoresist layer exposes a part of the second metal material layer in the first opening; and
and etching the second metal material layer by taking the patterned third photoresist layer as a mask to form the metal pad, wherein a space is formed between the side wall of the metal pad and the first metal material layer on the side wall of the first opening.
5. The method of fabricating a back-illuminated image sensor according to claim 4, wherein after etching the second metallic material layer and before etching the first metallic material layer, the method further comprises:
and forming a hard mask layer, wherein the hard mask layer covers the first metal material layer and the metal bonding pad.
6. The method of fabricating a back-illuminated image sensor of claim 5, wherein the method of forming a deep trench isolation structure and the metal grid comprises:
forming a fourth photoresist layer on the hard mask layer, and patterning the fourth photoresist layer to form a patterned fourth photoresist layer, wherein the patterned fourth photoresist layer exposes a region between adjacent shallow isolation trenches;
etching the hard mask layer by taking the patterned fourth photoresist layer as a mask to form a patterned hard mask layer;
removing the patterned fourth photoresist layer; and
and etching the first metal material layer by taking the patterned hard mask layer as a mask until the protective layer is exposed, so as to form a deep trench isolation structure and a metal grid which is positioned on the deep trench isolation structure and connected with the deep trench isolation structure in the pixel region.
7. The method of fabricating a back-illuminated image sensor of claim 6, wherein after forming the deep trench isolation structure and the metal grid, the method further comprises:
forming a fifth photoresist layer, wherein the fifth photoresist layer covers the patterned hard mask layer and the exposed protective layer;
patterning the fifth photoresist layer to form a patterned fifth photoresist layer, wherein the patterned fifth photoresist layer exposes the region where the metal pad is located;
etching the patterned hard mask layer by taking the patterned fifth photoresist layer as a mask to expose the metal bonding pad; and
and removing the patterned fifth photoresist layer.
8. The method of claim 5, wherein the material of the first metal material layer comprises tungsten, the material of the second metal material layer comprises aluminum, the material of the dielectric layer comprises a high dielectric constant material, the material of the protective layer comprises silicon oxide, and the material of the hard mask layer comprises silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof.
9. The method of fabricating a back-illuminated image sensor of claim 1, wherein after forming the deep isolation trench structure, the metal grid, and the grid pad connection layer, the method of fabricating further comprises: and forming a color filter film in the pixel region, wherein the color filter film is positioned between the metal grids and covers the metal grids.
10. A back-illuminated image sensor manufactured by the method for manufacturing a back-illuminated image sensor according to any one of claims 1 to 9.
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| CN202210745442.3A CN115000113B (en) | 2022-06-27 | Backside illuminated image sensor and manufacturing method thereof |
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