CN109817654A - Imaging sensor and forming method thereof - Google Patents
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Abstract
A kind of imaging sensor and forming method thereof, described image sensor includes: semiconductor substrate；A variety of filter, positioned at the surface of the semiconductor substrate, wherein there is pixel device in the semiconductor substrate below each filter；Isolation structure is located in the semiconductor substrate, and only a fraction pixel device is surrounded by the isolation structure to realize isolation；Wherein, the one part of pixel device includes the pixel device below one or more of filter: the filter for PDAF is to, full impregnated filter and long wavelength's light filter, wherein, long wavelength's light filter is used to filter out light of the wavelength less than preset wavelength threshold value and is greater than the light of the preset wavelength threshold value through wavelength.The present invention program facilitates the problem of mitigating dark current and white pixel.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to an image sensor and a forming method thereof.
Background
The image sensor is a core component of the image pickup apparatus, and realizes an image pickup function by converting an optical signal into an electric signal. Taking CMOS Image Sensors (CIS for short) as an example, CMOS Image Sensors are widely used in various fields because of their advantages of low power consumption and high signal-to-noise ratio.
Taking a Back-side Illumination (BSI) CIS as an example, in an existing manufacturing process, a logic device, a pixel device, and a metal interconnection structure are formed in and on a semiconductor substrate, then a carrier wafer is used to bond with a front surface of the semiconductor substrate, so as to thin a Back surface of the semiconductor substrate, and further a subsequent process of forming the CIS is formed on the Back surface of the semiconductor substrate, for example, a Grid-shaped grating (Grid) is formed on the Back surface of the semiconductor substrate of the pixel device, and a plurality of Color filters (Color filters) are formed in a Grid between the grids.
Specifically, the Color Filter may include an Infrared Filter (Infrared Color Filter), a Red Color Filter (Red Color Filter), a Green Color Filter (Green Color Filter), a Blue Color Filter (Blue Color Filter), a Clear Color Filter (Clear Color Filter), and a Filter pair for Phase Detection Auto Focus (PDAF). Wherein said fully transmissive filters, which may also be called White Color filters (White Color filters), are used to pass light of all colors.
In the prior art, a Back Deep Trench Isolation (BDTI) is generally used to isolate a Pixel device, however, during the formation of the Back Deep Trench Isolation, damage to a semiconductor substrate is easily induced, which causes a problem of Dark Current (Dark Current) and White Pixel (White Pixel) in the CIS.
Disclosure of Invention
The technical problem solved by the invention is to provide an image sensor and a forming method thereof, which are beneficial to reducing the problems of dark current and white pixels.
To solve the above technical problem, an embodiment of the present invention provides an image sensor, including: a semiconductor substrate; a plurality of color filters on a surface of the semiconductor substrate, wherein a pixel device is provided in the semiconductor substrate under each color filter; an isolation structure located within the semiconductor substrate, only a portion of the pixel devices being surrounded by the isolation structure to achieve isolation; wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value.
Optionally, the long wavelength light filter includes: a red filter and an infrared filter.
Optionally, each pixel device is surrounded by an ion implantation isolation region to achieve isolation, wherein the isolation structure is located in the ion implantation isolation region.
Optionally, the image sensor further includes: a grid-shaped grating structure located on the surface of the semiconductor substrate; wherein the color filters are respectively located in the respective grid openings of the grid structure.
To solve the above technical problem, an embodiment of the present invention provides a method for forming an image sensor, including: providing a semiconductor substrate; forming an isolation structure in the semiconductor substrate; forming a plurality of color filters on the surface of the semiconductor substrate, wherein pixel devices are arranged in the semiconductor substrate below each color filter, and only a part of the pixel devices are surrounded by the isolation structure to realize isolation; wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value.
Optionally, the long wavelength light filter includes: a red filter and an infrared filter.
Optionally, the isolation structure includes: the isolation groove and the dielectric material filling the isolation groove are formed in the substrate; alternatively, the isolation structure comprises: the isolation structure comprises an isolation groove, a dielectric material covering the bottom and the side wall of the isolation groove, and a metal material covering the dielectric material and filling the isolation groove.
Optionally, before forming the isolation structure in the semiconductor substrate, the method for forming the image sensor further includes: and forming an ion implantation isolation region in the semiconductor substrate, wherein each pixel device is surrounded by the ion implantation isolation region to realize isolation, and the isolation structure is positioned in the ion implantation isolation region.
Optionally, the forming of the ion implantation isolation region in the semiconductor substrate includes: forming the ion implantation isolation region by adopting an ion implantation process; wherein the implanted ions of the ion implantation process are selected from: boron ions.
Optionally, before forming the plurality of color filters on the surface of the semiconductor substrate, the method for forming the image sensor further includes: forming a grid-shaped grating structure on the surface of the semiconductor substrate; wherein the color filters are respectively located in the respective grid openings of the grid structure.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
in an embodiment of the present invention, there is provided an image sensor including: a semiconductor substrate; a plurality of color filters on a surface of the semiconductor substrate, wherein a pixel device is provided in the semiconductor substrate under each color filter; an isolation structure located within the semiconductor substrate, only a portion of the pixel devices being surrounded by the isolation structure to achieve isolation; wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value. By adopting the scheme, only a part of pixel devices are surrounded by the isolation structure to realize isolation, so that only the pixel devices which are more easily affected by optical crosstalk can be isolated, and compared with the prior art in which the isolation structure is arranged to isolate all the pixel devices, the isolation structure is beneficial to reducing the problems of dark current and white pixels. The isolation structure is arranged to isolate the pixel device below the color filter pair for PDAF, so that the focusing result of the PDAF is prevented from being influenced by optical crosstalk, and the accuracy of the focusing result of the PDAF is improved; the isolation structure is arranged to isolate the pixel devices below the full-transmission color filter, so that the influence of optical crosstalk on the pixel devices below the color filters of other surrounding colors is reduced under the condition that the full-transmission color filter can pass light of all colors; the isolation structure is arranged to isolate the long wavelength Light filter, which helps to avoid easy propagation to adjacent pixel devices due to deeper Light incidence when the Light wavelength is longer and the Angle Light (Angle Light) is difficult to be absorbed, thereby helping to reduce the influence of optical crosstalk.
Further, in the embodiment of the present invention, by providing the ion implantation isolation region, and each pixel device is surrounded by the ion implantation isolation region to implement isolation, all pixel devices, especially the pixel devices which are not surrounded by the isolation structure to implement isolation, can be electrically isolated by the ion implantation isolation region, thereby contributing to reducing the influence of electrical crosstalk.
Drawings
FIG. 1 is a top view of an image sensor of the prior art;
FIG. 2 is a cross-sectional view of FIG. 1 taken along cut line A1-A2;
FIG. 3 is a flow chart of a method of forming an image sensor in an embodiment of the invention;
FIG. 4 is a schematic cross-sectional view of a device corresponding to a part of the steps in a method for forming an image sensor according to an embodiment of the invention;
FIG. 5 is a top view of a first image sensor in an embodiment of the invention;
FIG. 6 is a cross-sectional view of FIG. 5 taken along cut line B1-B2;
FIG. 7 is a cross-sectional view taken along cut line C1-C2 of FIG. 5;
FIG. 8 is a top view of a second image sensor in an embodiment of the invention;
FIG. 9 is a cross-sectional view of FIG. 8 taken along cut line B3-B4;
FIG. 10 is a cross-sectional view of FIG. 8 taken along cut line C3-C4;
FIG. 11 is a top view of a third image sensor in an embodiment of the invention;
FIG. 12 is a cross-sectional view of FIG. 11 taken along cut line B5-B6;
FIG. 13 is a cross-sectional view of FIG. 11 taken along cut line C5-C6.
Detailed Description
In the prior art, BDTI is generally used to isolate a pixel device of an image sensor, however, in the process of forming BDTI, damage to a semiconductor substrate is easily induced, which causes problems of dark current and white pixel in a CIS.
Referring to fig. 1 and 2 together, fig. 1 is a top view of an image sensor in the prior art, and fig. 2 is a cross-sectional view of fig. 1 along cutting line a1-a 2. Wherein the top layer structure of the image sensor shown in fig. 1 is a color filter 150.
Specifically, the color filter 150 may include a blue color filter 151, a green color filter 152, a full-transmittance color filter 153, and a red color filter 154.
It is noted that in another specific implementation of the embodiment of the present invention, the color filter 150 may further include an infrared filter, a filter pair for PDAF, and other suitable filters, and in the embodiment of the present invention, there is no limitation on the category of the specific color filter.
In a specific implementation, the image sensor may include a semiconductor substrate 100, a pixel device, an ion implantation isolation region 120, an isolation structure 130, a grating structure 140, a color filter 150, and a lens structure 160.
The pixel device may be located in the semiconductor substrate 100, and the pixel device may further include a photodiode 102, a gate structure 112, and a source-drain doped region 114.
It is to be noted that the semiconductor substrate 100 may further include a structure located on the surface of the semiconductor substrate 100, such as the gate structure 112 and a metal interconnect structure (not shown), and is not limited to a portion inside the surface of the semiconductor substrate 100.
As shown in fig. 1, all pixel devices are surrounded by isolation structures 130 to achieve isolation.
The color filter 150 may be located on the front surface of the semiconductor substrate 100 and may also be located on the back surface of the semiconductor substrate 100. In the back-illuminated CIS shown in fig. 2, the color filter 150 is located on the rear surface of the semiconductor substrate 100.
Further, the image sensor may further include a grating structure 140, and the grating structure 140 may be formed on a surface of the semiconductor substrate to isolate incident light, thereby reducing optical crosstalk of incident light received through different filters. The Grid structure 140 may be a Metal Grid (Metal Grid).
The image sensor may further include a lens structure (Micro-lens)160, and the lens structure 160 may be used to capture incident light.
The inventor of the present invention has found that, in the prior art, pixel devices are all surrounded by an isolation structure 130 to achieve isolation, and during the formation of the isolation structure 130, the semiconductor substrate 100 needs to be etched first to form an isolation trench, and then the isolation trench is filled with an isolation material to form the isolation structure 130. However, when the semiconductor substrate 100 is etched, the semiconductor substrate is easily damaged by the etching process, which causes the problems of dark current and white pixels in the CIS.
In an embodiment of the present invention, there is provided an image sensor including: a semiconductor substrate; a plurality of color filters on a surface of the semiconductor substrate, wherein a pixel device is provided in the semiconductor substrate under each color filter; an isolation structure located within the semiconductor substrate, only a portion of the pixel devices being surrounded by the isolation structure to achieve isolation; wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value. By adopting the scheme, only a part of pixel devices are surrounded by the isolation structure to realize isolation, so that only the pixel devices which are more easily affected by optical crosstalk can be isolated, and compared with the prior art in which the isolation structure is arranged to isolate all the pixel devices, the isolation structure is beneficial to reducing the problems of dark current and white pixels. The isolation structure is arranged to isolate the pixel device below the color filter pair for PDAF, so that the focusing result of the PDAF is prevented from being influenced by optical crosstalk, and the accuracy of the focusing result of the PDAF is improved; the isolation structure is arranged to isolate the pixel devices below the full-transmission color filter, so that the influence of optical crosstalk on the pixel devices below the color filters of other surrounding colors is reduced under the condition that the full-transmission color filter can pass light of all colors; the isolation structure is arranged to isolate the long-wavelength light filter, so that when the wavelength of light is longer and angle light is difficult to absorb, the phenomenon that the light is easy to propagate to an adjacent pixel device due to deeper incidence is avoided, and the influence of optical crosstalk is reduced.
Referring to fig. 3, fig. 3 is a flowchart of a method for forming an image sensor according to an embodiment of the present invention. The image sensor forming method may include steps S21 to S23:
step S21: providing a semiconductor substrate;
step S22: forming an isolation structure in the semiconductor substrate;
step S23: forming a plurality of color filters on the surface of the semiconductor substrate, wherein a pixel device is arranged in the semiconductor substrate under each color filter, and only a part of the pixel devices are surrounded by the isolation structure to realize isolation, wherein the part of the pixel devices comprises the pixel devices under one or more of the following color filters: a filter pair for PDAF, a full-transmission filter, and a long wavelength light filter.
The long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold and transmitting light with the wavelength larger than the preset wavelength threshold.
The above steps will be described with reference to fig. 4 to 13.
Referring to fig. 4, fig. 4 is a schematic cross-sectional structure diagram of a device corresponding to a part of steps in a method for forming an image sensor according to an embodiment of the present invention.
A semiconductor substrate 200 is provided, and a pixel device may be provided in the semiconductor substrate 200, and the pixel device may include a photodiode 202, a gate structure 212, and a source-drain doped region 214.
The semiconductor substrate 200 may be a silicon substrate, or the material of the semiconductor substrate 200 may also be a material that is applied to an image sensor, such as germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the semiconductor substrate 200 may also be a silicon substrate on the surface of an insulator, a germanium substrate on the surface of an insulator, or a substrate on which an epitaxial layer (Epi layer) is grown. Preferably, the semiconductor substrate 200 may be a lightly doped semiconductor substrate, and the doping type is opposite to the drain region. Specifically, Deep Well doping (Deep Well Implant) may be implemented by performing ion implantation into the semiconductor substrate 200.
The photodiode 202 is capable of generating photo-generated carriers, such as electrons, when excited by external light. The photodiode 202 can be formed by an ion implantation process, and by controlling the energy and concentration of the ion implantation, the depth and implantation range of the ion implantation can be controlled, thereby controlling the depth and thickness of the photodiode 202.
It is to be noted that the semiconductor substrate 200 may further include a structure located on the surface of the semiconductor substrate 200, such as the gate structure 212 and a metal interconnection structure (not shown), and is not limited to a portion within the surface of the semiconductor substrate 200.
Wherein, an ion implantation isolation region 220 is formed in the semiconductor substrate 200, and each pixel device is surrounded by the ion implantation isolation region 220 to realize isolation.
Further, the step of forming the ion implantation isolation region 220 in the semiconductor substrate 200 may include: forming the ion implantation isolation region 220 by using an ion implantation process; the implantation ions of the ion implantation process may be selected from P-type ions, and may be boron (B) ions, for example.
In the embodiment of the present invention, by providing the ion implantation isolation region 220, and each pixel device is surrounded by the ion implantation isolation region 220 to achieve isolation, all pixel devices, especially the pixel devices which are not surrounded by the isolation structure to achieve isolation, can be electrically isolated by the ion implantation isolation region 220, thereby helping to reduce the influence of electrical crosstalk.
Further, an isolation structure is formed in the semiconductor substrate 200, and then a variety of color filters are formed on the surface of the semiconductor substrate 200.
Still further, the isolation structure may include: the isolation groove and the dielectric material filling the isolation groove are formed in the substrate; alternatively, the isolation structure comprises: the isolation structure comprises an isolation groove, a dielectric material covering the bottom and the side wall of the isolation groove, and a metal material covering the dielectric material and filling the isolation groove. Specifically, the isolation structure may be isolated by only using a filled dielectric layer, or may be isolated by filling an isolation trench with a stack of a dielectric film and a metal layer.
As a non-limiting example, the isolation structure may be formed by etching an isolation trench and then filling the isolation trench with a dielectric material or a metal material.
Referring to fig. 5, fig. 5 is a top view of a first image sensor according to an embodiment of the present invention, and the top layer structure of the image sensor shown in fig. 5 is a color filter 250 (without a grating structure).
Wherein the color filters 250 may include a blue color filter 251, a green color filter 252, a fully transmissive color filter 253, and a red color filter 254.
As shown in fig. 5, only a portion of the pixel devices, which may be the pixel devices under the all-transparent color filter 253, are surrounded by the isolation structure 230 to achieve isolation.
Referring to fig. 6 in combination with fig. 7, fig. 6 is a cross-sectional view taken along cutting line B1-B2 of fig. 5, and fig. 7 is a cross-sectional view taken along cutting line C1-C2 of fig. 5.
A grid-shaped grating structure 240 is formed on the surface of the semiconductor substrate 200 for isolating incident light, wherein the grating structure 240 may be a metal grating.
Further, color filters are formed, which are respectively located in the respective grid openings of the grid structure 240.
It is to be noted that the grating structure 240 and the color filter 250 may be located on the front surface of the semiconductor substrate 200, and may also be located on the back surface of the semiconductor substrate 200. In the back-illuminated CIS shown in fig. 6 and 7, the color filter 250 is located on the rear surface of the semiconductor substrate 200.
Further, a lens structure 260 is formed, which lens structure 260 may be used to capture incident light.
In the image sensor shown in fig. 6, only the pixel device under the full color filter 253 is surrounded by the isolation structure 230 to realize isolation, and the pixel device under the red color filter 254 is not surrounded by the isolation structure 230, that is, only when the red color filter 254 is adjacent to the full color filter 253, the isolation structure 230 is under the grid between the red color filter 254 and the full color filter 253.
In the image sensor shown in fig. 7, the green color filter 252 and the red color filter 254 are not surrounded by the isolation structure 230 to achieve isolation, and thus there is no isolation structure 230 under the grating between the green color filter 252 and the red color filter 254.
In the embodiment of the present invention, only a portion of the pixel devices is surrounded by the isolation structure 230 to achieve isolation, so that only the pixel devices more susceptible to optical crosstalk can be isolated, which is helpful to reduce the problems of dark current and white pixels compared to the prior art in which all the pixel devices are isolated by the isolation structure. Wherein the isolation structures 230 are provided to isolate the pixel devices under the fully transmissive color filters 254, which helps to reduce the effect of optical crosstalk on the pixel devices under color filters of other colors in the surroundings, in case the fully transmissive color filters 254 are able to pass light of all colors.
Referring to fig. 8, fig. 8 is a top view of a second image sensor in an embodiment of the present invention, and the top layer structure of the image sensor shown in fig. 8 is a color filter 250 (without a grating structure).
Wherein the color filters 250 may include a blue color filter 251, a green color filter 252, a fully transmissive color filter 253, and a red color filter 254.
As shown in fig. 5, only a portion of the pixel devices, which may be the pixel devices under the all-transparent color filter 253 and the red color filter 254, are surrounded by the isolation structure 330 to achieve isolation.
Referring to fig. 9 in combination with fig. 10, fig. 9 is a cross-sectional view taken along cutting line B3-B4 of fig. 8, and fig. 10 is a cross-sectional view taken along cutting line C3-C4 of fig. 8.
On the basis of the semiconductor device shown in fig. 4, a grid-shaped grating structure 240 is formed on the surface of the semiconductor substrate 200, and color filters are formed, and the color filters are respectively located in each grid opening of the grating structure 240, so that a lens structure 260 is formed.
In the image sensor shown in fig. 9, only the fully transmissive color filter 253 and the pixel device under the red color filter 254 are surrounded by the isolation structure 330 to achieve isolation, i.e., the isolation structure 330 is arranged under the grating between the red color filter 254 and the fully transmissive color filter 253.
As shown in fig. 10, in the image sensor, since only the pixel devices under the fully transmissive color filter 253 and the red color filter 254 are surrounded by the isolation structure 330 to achieve isolation, and the pixel devices under the green color filter 252 are not surrounded by the isolation structure 330, that is, only when the green color filter 252 is adjacent to the red color filter 254, the isolation structure 330 is under the grid between the green color filter 252 and the red color filter 254.
It is noted that in the embodiment of the present invention, the isolation structure 330 may be disposed to isolate the pixel device under the long wavelength light filter.
The long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold and transmitting light with the wavelength larger than the preset wavelength threshold.
Further, the long wavelength light filter may include: a red filter and an infrared filter.
In the embodiment of the present invention, the isolation structure 330 is disposed to isolate the long wavelength light filter, which helps to avoid the light from easily propagating to the adjacent pixel devices due to deeper light incidence when the light wavelength is longer and the angle light is difficult to be absorbed, thereby helping to reduce the influence of optical crosstalk.
In the embodiment of the present invention, only a portion of the pixel devices is surrounded by the isolation structure 330 to achieve isolation, so that only the pixel devices more susceptible to optical crosstalk can be isolated, which is helpful to reduce the problems of dark current and white pixels compared to the prior art in which all the pixel devices are isolated by the isolation structure. The isolation structure 330 is provided to isolate the pixel devices under the full-color-transparent filter 253, which helps to reduce the influence of optical crosstalk on the pixel devices under the color filters of other colors in the surroundings when the full-color-transparent filter 253 can pass through all colors of light; the isolation structure 330 is provided to isolate the long wavelength light filter, which helps to avoid the light from being incident deeper and easily propagating to the adjacent pixel devices when the light wavelength is longer and the angle light is difficult to be absorbed, thereby helping to reduce the influence of optical crosstalk.
For more details about the second image sensor, please refer to the description of the first image sensor in fig. 5 to 7, which is not repeated herein.
Referring to fig. 11, fig. 11 is a top view of a third image sensor in an embodiment of the present invention, and the top layer structure of the image sensor shown in fig. 11 is a color filter 450 (without a grating structure).
In the embodiment of the invention, in order to improve the performance of the optical image sensor, a Phase Detection Auto Focus (PDAF) technology is adopted for focusing, and the PDAF technology focuses based on the Phase difference principle, so that the focusing speed is improved, the focusing effect is improved, and the correct position of the lens is determined, so that the optical image sensor cannot normally work due to the fact that an image is in a defocused state.
In particular, to implement the PDAF technique, a focusing lens may be formed on the surface of a color filter pair for PDAF, which often employs two filters of the same color, for example, two red filters, two green filters, or two blue filters.
As shown in fig. 11, the color filter 450 may include a blue color filter 451, a green color filter 452, a red color filter 454, and a filter pair 455 for PDAF, among others.
As shown in fig. 11, only a portion of the pixel devices, which may be the pixel devices under the color filter pair 455 for the PDAF, is surrounded by the isolation structure 430 to achieve isolation. Wherein the color filter pair 455 for PDAF employs two green color filters.
Referring to fig. 12 in combination with fig. 13, fig. 12 is a cross-sectional view taken along cutting line B5-B6 of fig. 11, and fig. 13 is a cross-sectional view taken along cutting line C5-C6 of fig. 11.
On the basis of the semiconductor device shown in fig. 4, a grid-shaped grating structure 240 is formed on the surface of the semiconductor substrate 200, and then color filters are formed, and the color filters are respectively located in each grid opening of the grating structure 240, so that a lens structure 460 is formed.
As in the image sensor shown in fig. 12, since only the pixel device under the filter pair 455 for PDAF is surrounded by the isolation structure 430 to achieve isolation, and the pixel device under the blue filter 451 is not surrounded by the isolation structure 430, that is, only when the blue filter 451 is adjacent to the filter pair 455 for PDAF, the isolation structure 430 is under the grating between the blue filter 451 and the filter pair 455 for PDAF.
As in the image sensor shown in fig. 13, since only the pixel device under the color filter pair 455 for PDAF is surrounded by the isolation structure 430 to achieve isolation, that is, there is the isolation structure 430 under the grating surrounding the color filter pair 455 for PDAF.
In the embodiment of the present invention, only a portion of the pixel devices is surrounded by the isolation structure 430 to achieve isolation, so that only the pixel devices more susceptible to optical crosstalk can be isolated, which is helpful to reduce the problems of dark current and white pixels compared to the prior art in which all the pixel devices are isolated by the isolation structure. The isolation structure 430 is provided to isolate the pixel devices under the color filter pair 455 for PDAF, which helps to prevent the focusing result of PDAF from being affected by optical crosstalk, thereby improving the accuracy of the focusing result of PDAF.
For more details about the third image sensor, please refer to the description of the first image sensor in fig. 5 to 7, which is not repeated herein.
It should be noted that, in the embodiment of the present invention, only the pixel devices under a part of the filter pair for PDAF, the full-transmission filter, and the long-wavelength light filter may be selected to be isolated by the isolation structure, and the pixel devices under the filter pair for PDAF, the full-transmission filter, and the long-wavelength light filter may also be selected to be isolated by the isolation structure.
In an embodiment of the present invention, there is also provided an image sensor, referring to fig. 6, which may include: a semiconductor substrate 200; a plurality of color filters on a surface of the semiconductor substrate 200, wherein a pixel device is provided in the semiconductor substrate 200 under each color filter; an isolation structure 230 located in the semiconductor substrate, wherein only a part of the pixel devices are surrounded by the isolation structure 230 to realize isolation; wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: a pair of filters for PDAF, a full-transmission filter 253, and a long wavelength light filter for filtering light having a wavelength less than a preset wavelength threshold and transmitting light having a wavelength greater than the preset wavelength threshold.
Further, the long wavelength light filter may include: a red filter and an infrared filter.
Further, each pixel device is surrounded by an ion implantation isolation region 220 to achieve isolation, wherein the isolation structure 230 is located in the ion implantation isolation region 220.
Further, the image sensor may further include: a grid-shaped grid structure 240 located on the surface of the semiconductor substrate 200; wherein the color filters are respectively located in the respective grid openings of the grid structure 240.
For the principle, specific implementation and beneficial effects of the image sensor, please refer to the related description about the forming method of the image sensor shown in fig. 3 to fig. 13, which is not repeated herein.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. An image sensor, comprising:
a semiconductor substrate;
a plurality of color filters on a surface of the semiconductor substrate, wherein a pixel device is provided in the semiconductor substrate under each color filter;
an isolation structure located within the semiconductor substrate, only a portion of the pixel devices being surrounded by the isolation structure to achieve isolation;
wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value.
2. The image sensor of claim 1, wherein the long wavelength light filter comprises: a red filter and an infrared filter.
3. The image sensor of claim 1, wherein each pixel device is surrounded by an ion implantation isolation region to achieve isolation, wherein the isolation structure is located within the ion implantation isolation region.
4. The image sensor of claim 1, further comprising:
a grid-shaped grating structure located on the surface of the semiconductor substrate;
wherein the color filters are respectively located in the respective grid openings of the grid structure.
5. A method of forming an image sensor, comprising:
providing a semiconductor substrate;
forming an isolation structure in the semiconductor substrate;
forming a plurality of color filters on the surface of the semiconductor substrate, wherein pixel devices are arranged in the semiconductor substrate below each color filter, and only a part of the pixel devices are surrounded by the isolation structure to realize isolation;
wherein the portion of the pixel devices includes pixel devices under one or more of the following color filters: the PDAF color filter comprises a color filter pair used for PDAF, a full-transmission color filter and a long-wavelength light filter, wherein the long-wavelength light filter is used for filtering light with the wavelength smaller than a preset wavelength threshold value and transmitting light with the wavelength larger than the preset wavelength threshold value.
6. The method of claim 5, wherein the long wavelength light filter comprises: a red filter and an infrared filter.
7. The method of claim 5, wherein the image sensor is formed by,
the isolation structure includes: the isolation groove and the dielectric material filling the isolation groove are formed in the substrate;
or,
the isolation structure includes: the isolation structure comprises an isolation groove, a dielectric material covering the bottom and the side wall of the isolation groove, and a metal material covering the dielectric material and filling the isolation groove.
8. The method of claim 5, further comprising, prior to forming an isolation structure in the semiconductor substrate:
and forming an ion implantation isolation region in the semiconductor substrate, wherein each pixel device is surrounded by the ion implantation isolation region to realize isolation, and the isolation structure is positioned in the ion implantation isolation region.
9. The method of claim 8, wherein forming an ion implantation isolation region in the semiconductor substrate comprises:
forming the ion implantation isolation region by adopting an ion implantation process;
wherein the implanted ions of the ion implantation process are selected from: boron ions.
10. The method of claim 5, further comprising, before forming the plurality of color filters on the surface of the semiconductor substrate:
forming a grid-shaped grating structure on the surface of the semiconductor substrate;
wherein the color filters are respectively located in the respective grid openings of the grid structure.
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