CN110190075B

CN110190075B - Image sensor

Info

Publication number: CN110190075B
Application number: CN201910436611.3A
Authority: CN
Inventors: 杨鑫
Original assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Current assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Priority date: 2019-05-23
Filing date: 2019-05-23
Publication date: 2021-08-17
Anticipated expiration: 2039-05-23
Also published as: CN110190075A

Abstract

The embodiment of the invention discloses an image sensor, which comprises: the image sensor includes: a pixel unit constituting an array for sensing light; the array of sensitization includes a plurality of color channels, just it is provided with the isolation layer that is used for keeping apart the pixel to set up in preset position between the color channel to make the junction area difference of the photodiode's of different color channels PN junction.

Description

Image sensor

Technical Field

The present application relates to photodiode technology and relates to, but is not limited to, an image sensor.

Background

In the related art, the color filter such as (Red Green Blue, RGGB) has a low light utilization ratio in general, and the color filter configuration such as (Red Yellow Blue, RYYB) or (Red White Blue, RWWB) is liable to cause the situation that Y or W pixels are saturated early and R and B pixels are not saturated yet, and the color filter is not sufficiently utilized.

Disclosure of Invention

To solve the above technical problem, an embodiment of the present application provides an image sensor.

The technical scheme of the embodiment of the application is realized as follows:

an embodiment of the present application provides an image sensor, including:

a pixel unit constituting an array for sensing light;

the array of sensitization includes a plurality of color channels, just it is provided with the isolation layer that is used for keeping apart the pixel to set up in preset position between the color channel to make the junction area difference of the photodiode's of different color channels PN junction.

An embodiment of the present application provides an image sensor, including: a pixel unit constituting an array for sensing light;

the photosensitive array comprises a plurality of color channels, and an isolation layer for isolating pixels is arranged between the color channels at a preset position, so that the junction areas of PN junctions of the photodiodes under different color channels are different; therefore, the pixel isolation layer is arranged, so that the junction areas of PN junctions of different photodiodes are different, the saturation time of the photodiode with the small full-well capacitance is prolonged, the different photodiodes can be saturated at the same time, and the utilization efficiency of the image sensor is fully improved.

Drawings

FIG. 1 is a schematic diagram of a structure of an image sensor according to an embodiment of the present disclosure;

FIG. 2A is a schematic diagram of a photodiode according to an embodiment of the present disclosure;

FIG. 2B is a schematic diagram of a pixel unit according to an embodiment of the present disclosure;

FIG. 2C is a schematic diagram of a metal wiring of a photodiode according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram illustrating a structure of different color channels according to an embodiment of the present disclosure;

FIG. 4 is a color distribution diagram of a filter in the image sensor according to an embodiment of the present disclosure;

FIG. 5 is a schematic cross-sectional view of a pixel structure in an image sensor according to an embodiment of the present disclosure;

fig. 6 is a schematic structural diagram of an image sensor according to an embodiment of the present application.

Detailed Description

Before describing the technical solution of the embodiment of the present application in detail, a system architecture applied to the data transmission method of the embodiment of the present application is first briefly described. The data transmission method of the embodiment of the application is applied to related services of three-dimensional video data, such as services for sharing three-dimensional video data, live broadcast services based on three-dimensional video data, and the like. In this case, since the data amount of the three-dimensional video data is large, the depth data and the two-dimensional video data transmitted respectively need high technical support in the data transmission process, and thus the mobile communication network is required to have a high data transmission rate and a stable data transmission environment.

In order to facilitate a better understanding of the invention, in the embodiments of the present application, the following explanations are made with respect to color filters capable of implementing a color program: the bayer color filter is a mosaic color filter array formed by arranging RGB color filters on a square of a photo-sensing assembly. Single-chip digital image sensors used in digital cameras, video recorders, scanners, etc. mostly use color filter arrays of this specific arrangement to produce color images. Such an arrangement of filters is also called RGBG, GRGB or RGGB, since 50% is green, 25% is red and the other 25% is blue. In addition to RGGB, color filters such as RWWB, RYYB, or CMY can realize color imaging.

An embodiment of the present application provides an image sensor, fig. 1 is a schematic structural diagram of the image sensor in the embodiment of the present application, and as shown in fig. 1, the image sensor includes:

a pixel unit 101 constituting an array for light sensing;

the photosensitive array comprises a plurality of color channels (namely a White channel (W channel) 102 and a Red channel (Red channel, R channel) 103), and an isolation layer 104 for isolating pixels is arranged between the color channels at preset positions, so that the junction areas of PN junctions of photodiodes under different color channels are different; wherein the W channel 102 may be understood as being free of filters.

Here, the ratio of the full-well capacitance of the photodiodes of the two color channels provided with the spacer layer is matched with the ratio of the light incoming amounts of the two color channels. For example, if the spacer is provided between the W channel and the R channel, the ratio of the amount of light entering between the W channel and the R channel is the same as the ratio between the full-well capacitance of the photodiode under the W channel and the full-well capacitance of the photodiode under the R channel. Each color channel at least comprises a photodiode; the plurality of color channels includes at least: r channel, blue channel, yellow channel, and W channel. The isolation layer is made of metal or dielectric material; the dielectric material may be an oxide material, a nitride material, an oxynitride material, or the like. The preset position is determined according to the ratio of the quantum efficiencies of the photodiodes under two color channels adjacent to the preset position; the quantum efficiency is the ratio of the average number of photons generated by the photodiode in a unit time under a certain specific wavelength to the number of incident photons, and is used for representing the photoelectric conversion capability of the photodiode. If the quantum efficiency of the photodiode under the first color channel in the two color channels is greater than that of the photodiode under the second color channel, the preset position is close to the photodiode under the second color channel, so that the junction area of the PN junction of the photodiode under the second channel is greater than that of the PN junction of the photodiode under the first channel, and therefore the capacitances of the photodiode under the second channel and the photodiode under the first channel are guaranteed, and saturation is achieved at the same time.

In this embodiment, when the isolation layer is disposed between two color channels, a difference between times at which pixels in the two color channels reach saturation is smaller than a preset time difference. For example, since the amount of light entering the W channel is greater than that of the R channel, the time for the pixel of the W channel to reach saturation is less than that of the pixel of the red channel, so that when the W channel is saturated, the red channel is still a distance away from saturation, which results in the waste of the R channel signal. In this embodiment, to solve this problem, an isolation layer is disposed between the R channel and the W channel to increase the junction area of the PN junction of the photodiode in the W channel, thereby increasing the full-well capacitance of the photodiode in the W channel, so as to prolong the time for the pixel in the W channel to reach saturation, and increase the pixel in the W channel and the pixel in the R channel to reach saturation at the same time, thereby improving the utilization rate of the image sensor.

In the embodiment of the application, the pixel isolation layer is arranged between the diodes of different color channels, so that the junction area of the PN junction of the photodiode with smaller full-well capacitance is increased, the saturation time of the photodiode is increased, different photodiodes can be saturated at the same time, and the utilization rate of the image sensor is improved.

An embodiment of the present application provides an image sensor, where fig. 2A is a schematic view of a structure of a photodiode according to an embodiment of the present application, and as shown in fig. 2A, each color channel at least includes one photodiode, where the photodiode includes:

a substrate 201 for supporting the electrical properties of the photodiode.

The silicon pillar 202, the bottom surface of which is the substrate, is used for injecting a preset amount of phosphorus ions (p ions) 203 into the silicon pillar to form an inversion layer 204.

Here, the photodiode may be a P-type photodiode, and after the P-type cylindrical Si pillar 202 is implanted with the n-well (i.e., after the P-type cylindrical silicon pillar 202 is implanted with the phosphorous ion 203), a PN junction of the photodiode is formed, and a predetermined amount of P-ions is implanted into the surface of the cylindrical silicon pillar, so that an inversion layer is formed. For example, after P ions are added to the P-type cylindrical silicon pillar 202, a forward voltage is generated, and an electric field generated by the forward voltage repels holes and attracts electrons, so that holes in the substrate near the gate of the photodiode are repelled, and electrons in the P-type substrate are attracted to the surface of the substrate under the gate, but when the positive gate-source voltage reaches a certain value, the electrons form an N-type thin layer, i.e., an inversion layer, on the surface of the P-type cylindrical silicon pillar near the gate.

The inversion layer 204 is located inside the silicon pillar 202, and is used for recombining with the hole 205 in the silicon pillar 202 to eliminate a part of electrons in the silicon pillar 202;

here, since a large amount of phosphorus ions are injected into the cylindrical silicon pillar 202, that is, the surface of the cylindrical silicon pillar 202 is cut off, some surface carbon exists at the cut-off surface, so that electrons are generated and cross-sectional areas exist, and surface current is generated; in this embodiment, the intermediate energy level of the electron is removed by recombination of the inversion layer and the hole, thereby reducing the surface current.

A depletion layer 206 is located inside the silicon pillar 202.

In this embodiment, the plurality of color channels at least includes: r channel, blue channel, yellow channel, and W channel. When the color channels are R channels and W channels, firstly determining the preset position according to the ratio of the quantum efficiency of the photodiode of the R channel to the quantum efficiency of the photodiode of the W channel, and then arranging the pixel isolation layer at the preset position to enable the junction area of the PN junction of the photodiode under the W channel to be larger than the junction area of the PN junction of the photodiode under the R channel; as shown in fig. 5, the isolation layer 501 is in an inclined state, and the preset position where the isolation layer 501 is placed is closer to the R channel 502 and farther from the W channel 503, so that although the light incoming amount of the W channel is greater than that of the red channel, in this embodiment, the isolation layer 501 is disposed between the R channel 502 and the W channel 503, so that the junction area 505 of the PN junction of the photodiode under the W channel is greater than the junction area 504 of the PN junction of the photodiode under the R channel, thereby increasing the full-well capacitance of the photodiode under the W channel, and enabling the pixels of the photodiodes of two color channels to be saturated simultaneously.

An embodiment of the present application provides an image sensor, and fig. 2B is a schematic structural diagram of a pixel unit in an embodiment of the present application, and as shown in fig. 2B, the pixel unit includes:

a photodiode 211 and a photodiode 212, wherein the photodiode 211 is a photodiode under an R channel 213, and the photodiode 212 is a photodiode under a W channel 214.

A transfer transistor 215 for transferring charge generated by the photosensitive array to a floating diffusion region 217.

Here, for example, after the transfer transistor 215 is turned on by the power supply 218, the charge in the photodiode is transferred to the floating diffusion region by the transfer transistor 215; the floating diffusion region is used to store charge in the plurality of photodiodes.

A readout circuit 216 for reading out the charge transferred into the floating diffusion region.

Here, the readout circuit 216 outputs the charges stored in the floating diffusion region.

The readout circuit 216 further includes:

a reset transistor 261 connected to the floating diffusion region for resetting the floating diffusion region.

And an amplifying transistor 262 connected to the floating diffusion region for amplifying the charge in the floating diffusion region to obtain an amplified charge.

And a selection transistor 263 connected to the amplification transistor 262 for reading out the amplified charges to an output circuit.

The output circuit is connected to the selection transistor 263, and is configured to output the amplified charge.

As can be seen from fig. 2B, under the same light receiving surface condition, the junction area 240 of the PN junction under the W channel 214 is much larger than the junction area 230 of the PN junction under the R channel 213, so that the full-well capacitance of the W channel 214 is ensured to be larger than that under the R channel 213, so that the W channel 214 and the R channel 213 can reach saturation at the same time, and the same design is also applicable to the photodiode under the B channel.

In the present embodiment, the metal wiring patterns of the

diodes

211 and 212 in fig. 2B, as shown in fig. 2C, the metal wiring pattern of the diode 211 is 21, and the metal wiring pattern of the diode 212 is 22; as can be seen from fig. 2C, the metal wiring patterns of the

diodes

211 and 212 are the same, thereby ensuring that the internal circuits of the

diodes

211 and 212 are the same and the same output circuit can be shared.

In the embodiment of the application, the isolation layers are arranged among the plurality of color channels of one pixel unit of the image sensor, so that the junction area of the PN junction of the photodiode is changed, the full-well capacitance of the photodiode under different color channels is changed, and the pixels of different color channels are saturated at the same time.

In the related art, a color filter such as RGGB has a low light utilization ratio, and the use of such a color filter is insufficient in a case where pixels of Y channel or W channel are saturated and pixels of R channel and B channel are not saturated due to a color filter configuration such as RYYB or RWWB. Fig. 3 is a schematic diagram of a composition structure of different color channels according to an embodiment of the present application, and as shown in fig. 3, on-

chip lenses

31, 32, and 33 respectively correspond to a B channel 301, an R channel 302, and a Y channel 303; the photodiodes under the B channel 301, R channel 302, and Y channel 303 are 34, 35, and 36, respectively; the

photodiode metal wiring

34, 35, and 36 is 304, 305, and 306, respectively. However, in the related art, the full-well capacitances of the photodiodes in the R channel 302, the B channel 301, and the Y channel 303 are the same, which means that the received light intensities are the same when all the pixels are saturated, which causes a problem that when the Y channel 303 is saturated, the R channel 302 and the B channel 301 are far from each other and are not saturated, which results in a waste of signals in the R channel 302 and the B channel 301.

Based on this, the embodiment of the present application provides an image sensor, which specifically includes: the filter consists of red (R), white (i.e. no filter) and blue, wherein the red accounts for 25%, the blue accounts for 25%, and the filter does not exist in other places and accounts for 50%. Meanwhile, the full-well capacitance of the photodiode under the W channel is higher than that of the photodiode under the R channel and the B channel by adjusting the isolation region through the pixel isolation layer.

Fig. 4 is a color distribution diagram of a filter in the image sensor according to the embodiment of the present application, as shown in fig. 4, if 4 adjacent pixels are combined into a module from the leftmost red pixel 401, the composition of each module is the same, that is, in each module, a wave plate is composed of red (R)401, white (W)402, and blue (B)403, where red 401 accounts for 25%, blue 402 accounts for 25%, and no filter exists elsewhere, accounting for 50%. In other embodiments, it is also possible to start with white 402, and then every four adjacent pixels are arranged in combination as WRBW; or, starting with blue 402, every fourth adjacent pixel combination is arranged to be BWWR.

Fig. 5 is a schematic cross-sectional view of a pixel structure in an image sensor according to an embodiment of the present invention, as shown in fig. 5, taking an R channel 502 and a W channel 503 as an example, since the light receiving surfaces of the photodiode pixels under the original R channel 502 and the W channel 503 which penetrate through the on-

chip lenses

51 and 52 are the same, but since the pixel isolation layer 501 is an oblique isolation layer, the junction area 505 of the PN junction under the W channel 503 is larger than the junction area 504 of the PN junction under the R channel 502, which means that the full-well capacitance of the W channel 503 is larger than the full-well capacitance of the R channel 502, so that the pixels of the W channel 503 and the R channel 502 can be saturated at the same time or within a small time difference.

In the present embodiment, the ratio of the full-well capacitance may be determined based on the ratio of the light amount of the W channel 503 to the light amount of the R channel 502; for example, the amount of light entering the W channel 503 is larger than the amount of light entering the R channel 502, and the position of the spacer 501 in the isolation region is determined according to the ratio of the amounts of light entering the W channel 503 to the R channel 502 so that the ratio of the junction area of the photodiode PN junction of the W channel 503 to the junction area of the photodiode PN junction of the R channel 502 is the same as the ratio of the amounts of light entering the W channel.

Based on the foregoing embodiments, an embodiment of the present invention provides an electronic device, and fig. 6 is a schematic view of a composition structure of an image sensor provided in an embodiment of the present application, and as shown in fig. 6, the image sensor 600 includes:

a pixel unit 601 constituting an array for light sensing;

the photosensitive array comprises a plurality of color channels 602, and an isolation layer for isolating pixels is arranged between the color channels at preset positions, so that the junction areas of the PN junctions of the photodiodes 603 under different color channels are different.

In other embodiments, the predetermined position is determined according to a ratio of quantum efficiencies of the photodiodes in two color channels adjacent to the predetermined position.

In other embodiments, at least one photodiode is included under each color channel.

In other embodiments, the ratio between the full-well capacitances of the photodiodes of the two color channels provided with the isolation layer matches the ratio between the amounts of incident light of the two color channels.

In other embodiments, when the plurality of color channels are a red channel and a white channel, a separation layer is disposed at the preset position between the red channel and the white channel, so that a junction area of a PN junction of the photodiode under the white channel is larger than a junction area of a PN junction of the photodiode under the red channel.

In other embodiments, the isolation layer is a metallic texture or a dielectric material.

In other embodiments, when the isolation layer is disposed between two color channels, a difference between times at which pixels in the two color channels reach saturation is smaller than a preset time difference.

In other embodiments, the photodiode includes:

a substrate;

the bottom surface of the silicon column is the substrate and is used for injecting a preset amount of phosphorus ions into the silicon column to form an inversion layer;

the inversion layer is positioned in the silicon column and is used for being compounded with holes in the silicon column so as to eliminate partial electrons in the silicon column;

the depletion layer is positioned inside the silicon column.

In other embodiments, the pixel unit further includes:

a transfer transistor for transferring charge generated by the photosensitive array to the floating diffusion region;

a readout circuit for reading out the charge transferred into the floating diffusion region.

In other embodiments, the readout circuit includes:

a reset transistor connected to the floating diffusion region for resetting the floating diffusion region;

the amplifying transistor is connected with the floating diffusion region and used for amplifying the charges in the floating diffusion region to obtain amplified charges;

a selection transistor connected to the amplification transistor for reading out the amplified charge to an output circuit;

the output circuit is connected with the selection transistor and is used for outputting the amplified charges.

It should be noted that: in the above embodiment, when the electronic device performs image capturing, only the division of the program modules is taken as an example, and in practical applications, the processing may be distributed to different program modules according to needs, that is, the internal structure of the electronic device is divided into different program modules to complete all or part of the processing described above.

In the several embodiments provided in the present application, it should be understood that the disclosed method and intelligent device may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only a logical functional division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all functional units in the embodiments of the present application may be integrated into one second processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

Those of ordinary skill in the art will understand that: all or part of the steps for implementing the embodiments can be implemented by hardware related to program instructions, and the program can be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: a removable storage device, a ROM, a RAM, a magnetic or optical disk, or various other media that can store program code.

Alternatively, the integrated units described above in the present application may be stored in a computer-readable storage medium if they are implemented in the form of software functional modules and sold or used as independent products. Based on such understanding, the technical solutions of the embodiments of the present application may be essentially implemented or portions thereof contributing to the prior art may be embodied in the form of a software product stored in a storage medium, and including instructions for causing a computer device (which may be a personal computer, a server, or a mobile phone) to execute all or part of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a removable storage device, a ROM, a RAM, a magnetic or optical disk, or various other media that can store program code.

It should be noted that: the technical solutions described in the embodiments of the present application can be arbitrarily combined without conflict.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application.

Claims

1. An image sensor, comprising:

a pixel unit constituting an array for sensing light;

the photosensitive array comprises a plurality of color channels, and an isolation layer for isolating pixels is arranged between the color channels at a preset position, so that the junction areas of PN junctions of the photodiodes under different color channels are different; wherein the preset position is determined according to the ratio of the quantum efficiencies of the photodiodes in the two color channels adjacent to the preset position.

2. The image sensor of claim 1, wherein at least one photodiode is included under each color channel.

3. The image sensor according to claim 1, wherein a ratio between full-well capacitances of photodiodes of two color channels provided with the isolation layer matches a ratio between incident light amounts of the two color channels.

4. The image sensor of claim 3, wherein when the plurality of color channels are a red channel and a white channel, a spacer layer is disposed at the preset position between the red channel and the white channel to make a junction area of a PN junction of the photodiode under the white channel larger than a junction area of a PN junction of the photodiode under the red channel.

5. The image sensor of claim 1, wherein the isolation layer is a metallic material or a dielectric material.

6. The image sensor of claim 1, wherein when the spacer layer is disposed between two color channels, pixels in the two color channels are saturated at the same time.

7. The image sensor of any of claims 1 to 6, wherein the photodiode comprises:

a substrate;

the depletion layer is positioned inside the silicon column.

8. The image sensor of claim 1, wherein the pixel cell further comprises:

9. The image sensor of claim 8, wherein the readout circuit comprises: