CN110677606B - Pixel structure, CIS and terminal - Google Patents
Pixel structure, CIS and terminal Download PDFInfo
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- CN110677606B CN110677606B CN201910872957.8A CN201910872957A CN110677606B CN 110677606 B CN110677606 B CN 110677606B CN 201910872957 A CN201910872957 A CN 201910872957A CN 110677606 B CN110677606 B CN 110677606B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/79—Arrangements of circuitry being divided between different or multiple substrates, chips or circuit boards, e.g. stacked image sensors
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Abstract
The embodiment of the application discloses a pixel structure, which comprises a first layer PD, a second layer PD, a first reading circuit and a second reading circuit, wherein the first layer PD comprises a PD, the PDs are respectively used for carrying out resonance absorption and photoelectric conversion on light with corresponding specific wavelengths in received incident light to obtain electric signals corresponding to the light with the two specific wavelengths, the second layer PD is placed on one side of the first layer PD and comprises two PDs, the two PDs are used for carrying out resonance absorption and photoelectric conversion on light with the two specific wavelengths in the incident light after the resonance absorption of the first layer PD to obtain electric signals corresponding to the light with the two specific wavelengths, the first reading circuit reads out the electric signals corresponding to the light with the one specific wavelength, and the second reading circuit reads out the electric signals corresponding to the light with the two specific wavelengths. The embodiment of the application also provides a CIS and a terminal.
Description
Technical Field
The present invention relates to a pixel structure of a Complementary Metal Oxide Semiconductor Image Sensor (CIS) in a terminal, and more particularly, to a pixel structure, a CIS, and a terminal.
Background
Generally, a digital camera using a Charge-coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) is capable of recording only one of three colors of Red, Green and Blue (RGB) on the same pixel structure, currently, Foveon X3 is the first image sensor in the world capable of capturing all colors on one pixel structure, Foveon X3 uses a three-layer stacked photosensitive element, and measures signals obtained at different depths by using the difference of absorption lengths of light with different wavelengths in silicon, each layer records one of color channels of RGB, and finally, the detection of three colors of R, G, and B is realized in one pixel structure.
However, the Foveon X3 adopts a three-layer laminated photosensitive element, which has high process difficulty, high power consumption and serious spectral crosstalk, and affects the quality of signals obtained by a pixel structure, and further affects the imaging quality of the CIS.
Disclosure of Invention
The embodiment of the application provides a pixel structure, a CIS and a terminal, and aims to improve the signal quality of an electric signal obtained by the pixel structure.
The technical scheme of the application is realized as follows:
the embodiment of the application provides a pixel structure, which comprises a first layer PD, a second layer PD, a first readout circuit connected with the first layer PD and a second readout circuit connected with the second layer PD; wherein the content of the first and second substances,
The first layer PD comprises a PD, and the PD is used for carrying out resonance absorption and photoelectric conversion on light with a corresponding specific wavelength in received incident light to obtain an electric signal corresponding to the light with the specific wavelength;
the second layer PD is arranged on one side of the first layer PD, and comprises two PDs which are used for performing resonance absorption and photoelectric conversion on the light with two corresponding specific wavelengths in the incident light subjected to resonance absorption by the first layer PD to obtain electric signals corresponding to the light with the two specific wavelengths;
the first readout circuits respectively read out the electric signals corresponding to the light with the specific wavelength;
the second reading circuit reads out electric signals corresponding to the two kinds of light with the specific wavelengths;
wherein any two PDs in the first layer PD and the second layer PD are different from each other.
The embodiment of the application also provides a CIS, which comprises the pixel structure described in one or more embodiments.
The embodiment of the application further provides a terminal, and the terminal comprises the CIS in one or more embodiments.
The embodiment of the application provides a pixel structure, a CIS and a terminal, the pixel structure comprises a first layer PD, a second layer PD, a first readout circuit connected with the first layer PD and a second readout circuit connected with the second layer PD, wherein the first layer PD comprises a PD, the PD is used for performing resonance absorption and photoelectric conversion on light with a corresponding specific wavelength in received incident light to obtain an electric signal corresponding to the light with the specific wavelength, the second layer PD is arranged on one side of the first layer PD and comprises two PDs, the two PDs are respectively used for performing resonance absorption and photoelectric conversion on light with two specific wavelengths in the incident light after the resonance absorption of the first layer PD to obtain electric signals corresponding to the light with the two specific wavelengths, any two PDs in the first layer PD and the second layer PD are different from each other, the first readout circuit respectively reads out the electric signals corresponding to the light with the specific wavelength, the second reading circuit reads out the electric signals corresponding to the light with two specific wavelengths; that is to say, in the embodiment of the present application, one PD is disposed in the first PD layer, and two PDs different from the one PD are disposed in the second PD layer, so that the pixel structure can perform resonance absorption and photoelectric conversion on incident light in a layered manner, and thus, electrical signals corresponding to light with three specific wavelengths can be obtained, and the problems of high process difficulty, high power consumption and serious crosstalk caused by using a conventional three-layer stacked structure are avoided, so that the quality of signals obtained by the pixel structure is improved, and the imaging quality of the CIS is improved.
Drawings
FIG. 1 is a schematic representation of wavelength dependence on absorption coefficient and penetration depth, respectively;
FIG. 2 is a schematic cross-sectional view of Foveon X3;
fig. 3 is a schematic structural diagram of an alternative pixel structure according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of an example of an alternative optical filter provided in an embodiment of the present disclosure;
fig. 5A is a schematic structural diagram of an example of an alternative pixel structure provided in an embodiment of the present application;
fig. 5B is a schematic structural diagram of an example of another alternative pixel structure provided in the embodiments of the present application;
fig. 5C is a schematic structural diagram of an example of yet another alternative pixel structure provided in the embodiments of the present application;
fig. 6 is a schematic cross-sectional view of an example of an alternative pixel structure provided in an embodiment of the present application;
fig. 7 is a schematic structural diagram of an example of yet another alternative pixel structure provided in an embodiment of the present application;
fig. 8 is a schematic structural diagram of an alternative CIS provided in an embodiment of the present application;
fig. 9 is a schematic structural diagram of an alternative terminal according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.
Example one
Currently, Foveon X3 is the first image sensor that can capture all colors on a pixel structure globally, fig. 1 is a schematic diagram of wavelength as a function of absorption coefficient and penetration depth, respectively, as shown in fig. 1, the abscissa is wavelength and is in μm, and the ordinate includes the absorption coefficient as the left ordinate and is in/cm, and also includes the penetration depth as the right ordinate and is in μm, as can be seen from fig. 1, light with different wavelengths has different absorption coefficients in silicon, and as the wavelength increases, the absorption coefficient becomes smaller, the penetration depth of light with different wavelengths in silicon is different, and as the wavelength increases, the penetration depth becomes larger.
FIG. 2 is a schematic cross-sectional structure diagram of Foveon X3, as shown in FIG. 2, Foveon X3 includes a drain forward extending nldd, a p-well, an n-well, and a p-substrate in sequence from the top surface to the bottom surface, where the drain forward extending nldd has a thickness of 0.2 μm, the p-well has a thickness of 0.6 μm, the n-well has a thickness of 2 μm, the p-well is used for collecting blue photons, an electrical signal ib after photoelectric conversion of the blue photons can be measured between the drain forward extending nldd and the p-well, an electrical signal ig after photoelectric conversion of the green photons can be measured between the p-well and the n-well, an electrical signal ir after photoelectric conversion of the red photons can be measured between the n-well and the p-substrate, and thus, based on the relationship between the wavelength and the absorption coefficient and penetration depth respectively given in FIG. 1, a Foveon X3 three-layer photosensitive element given in FIG. 2, each layer records one color channel of RGB, and finally detection of three colors of R, G and B is realized in one pixel structure.
However, the conventional Foveon X3 has high power consumption, large heat, large pixel structure size, large data volume, low frame rate, relatively serious spectral crosstalk (crosstalk), relatively complicated RGB reduction algorithm, inaccurate color, poor color expression under high light sensitivity (ISO) less than or equal to 100, and high color noise under low light.
In order to improve the signal quality of an electrical signal obtained by a pixel structure, an embodiment of the present application provides a pixel structure, fig. 3 is a schematic structural diagram of an alternative pixel structure provided by an embodiment of the present application, and referring to fig. 3, the pixel structure may include a first layer PD31, a second layer PD32, a first readout circuit 33 connected to the first layer PD, and a second readout circuit 34 connected to the second layer PD; wherein, the first and the second end of the pipe are connected with each other,
the first layer PD31 includes a PD for resonance absorption and photoelectric conversion of light with a specific wavelength in the received incident light to obtain an electrical signal corresponding to the light with the specific wavelength;
the second layer PD32 is placed on one side of the first layer PD31, the second layer PD32 comprises two kinds of PDs, and the two kinds of PDs are respectively used for performing resonance absorption and photoelectric conversion on two kinds of light with specific wavelengths which correspond to each other in incident light subjected to resonance absorption by the first layer PD31 to obtain electric signals corresponding to the light with the two kinds of specific wavelengths;
The first readout circuit 33 reads out an electric signal corresponding to light of a specific wavelength;
the second readout circuit 34 respectively reads out the electrical signals corresponding to the two lights with specific wavelengths;
wherein any two kinds of PDs in the first layer PD and the second layer PD are different from each other.
Specifically, in the pixel structure, the PDs are divided into two layers, namely a first layer PD31 and a second layer PD32, where the first layer PD31 includes one PD, where the number of one PD may be 1 or more than 1, and the second layer PD32 includes two PDs, where the number of each PD in the two PDs may be 1 or more than 1, the number of the two PDs may be the same or different, and the interval between the PDs in the first layer PD31 and the second layer PD32 may be equal or not, and embodiments of the present application are not particularly limited.
Each of the first layer PD and the second layer PD corresponds to a specific wavelength, and each PD respectively resonantly absorbs and photoelectrically converts the corresponding specific wavelength, so that incident light passing through the first layer PD31 can obtain an electrical signal corresponding to light with a specific wavelength, for example, when the wavelength of red light with a specific wavelength is used, the first layer PD31 photoelectrically converts the electrical signal corresponding to the wavelength of red light.
Here, the incident light is transmitted to the second layer PD32 after being resonance-absorbed, and the second layer PD32 performs resonance absorption and photoelectric conversion on two specific wavelengths of light other than the light of the one specific wavelength among the incident light resonance-absorbed by the first layer PD31, and obtains electric signals corresponding to the two specific wavelengths of light, which are light other than the light of the one specific wavelength among three color lights, for example, when the one specific wavelength is a red wavelength, the two specific wavelengths are a blue wavelength and a green wavelength, respectively.
In this way, the second layer PD32 can obtain electrical signals corresponding to the remaining two specific wavelengths of the three-color light, that is, the pixel structure of the layered PD can obtain electrical signals corresponding to the three-color light, so that the pixel structure can obtain electrical signals corresponding to the three-color light.
Therefore, by adopting the double-layer PD structure, the pixel structure can absorb optical signals in a visible light wave band, the signal quantity of electric signals obtained by the first layer PD31 in the pixel structure is improved, the signal to noise ratio of the CIS and the resolving power of the CIS can be further improved by combining the signals obtained by the second layer PD32 in the pixel structure, and the false color in the demosaicing process is reduced.
Further, since the pixel size of the pixel structure is in the sub-wavelength range, in order to enable the PD to realize resonance absorption, in an alternative embodiment, when the first layer PD includes the first type PD, the second layer PD includes the second type PD and the third type PD;
the first PD is used for carrying out resonance absorption on light with a first specific wavelength in received incident light according to the resonance wavelength of a light receiving surface of the first PD, and carrying out photoelectric conversion on the absorbed light to obtain an electric signal corresponding to the light with the first specific wavelength;
the second PD is used for carrying out resonance absorption on light with a second specific wavelength in the received incident light after the resonance absorption of the first layer PD according to the resonance wavelength of the light receiving surface of the second PD, and carrying out photoelectric conversion on the absorbed light to obtain an electric signal corresponding to the light with the second specific wavelength;
the third PD is used for carrying out resonance absorption on light with a third specific wavelength in the received incident light after the resonance absorption of the first layer of PD according to the resonance wavelength of the light receiving surface of the third PD, and carrying out photoelectric conversion on the absorbed light to obtain an electric signal corresponding to the light with the third specific wavelength;
a first readout circuit reads out an electric signal corresponding to light of a first specific wavelength;
The second reading circuit respectively reads the electric signals corresponding to the light with the second specific wavelength and the electric signals corresponding to the light with the third specific wavelength;
wherein the resonance wavelength of the light receiving face of each of the first, second, and third PDs is a wavelength at which resonance absorption occurs at the light receiving face of each PD.
That is, the first PD included in the first PD31, the second PD included in the second PD32, and the third PD are respectively resonance-absorbed by the first PD having the first specific wavelength, the second PD having the second specific wavelength, and the third PD having the third specific wavelength according to the resonance wavelength of the light receiving surface, that is, the first PD can resonance-absorb the light having the first specific wavelength, the second PD can resonance-absorb the light having the second specific wavelength, and the third PD can resonance-absorb the light having the third specific wavelength.
Here, the photoelectric conversion efficiency of each PD is further improved due to the resonance absorption of each PD, and further, the signal quality of an electric signal obtained by the pixel structure is improved, which also improves the imaging quality of the CIS.
It should be noted that each PD in the above-described pixel structure absorbs a specific wavelength by using a resonance wavelength of its light-receiving surface, which is related to a refractive index of the light-receiving surface of the PD and a size of the light-receiving surface of the PD, so that the resonance wavelength of the light-receiving surface of the PD can be adjusted by adjusting the refractive index of the light-receiving surface of the PD and/or adjusting the size of the light-receiving surface of the PD.
In general, the resonance wavelength of the light receiving surface of the PD is adjusted by adjusting the size of the light receiving surface of the PD so that the specific wavelength is within the range of the resonance wavelength of the light receiving surface of the PD, thereby causing the light receiving surface of the PD to achieve resonance absorption for light of the specific wavelength; thus, the light absorption amount of each PD can be increased, thereby increasing the light absorption amount of the entire pixel structure, and also enhancing crosstalk between two pixel structures, which affects image quality.
In an alternative embodiment, the first specific wavelength, the second specific wavelength and the third specific wavelength include:
any one combination of the following three wavelengths: red, green, blue wavelengths.
Specifically, the first specific wavelength may be a red wavelength, or a green wavelength, or a blue wavelength, for example, when the first specific wavelength is a red wavelength, the second specific wavelength may be a green wavelength, and the third specific wavelength may be a blue wavelength; when the first specific wavelength is a red wavelength, the second specific wavelength may be a blue wavelength, and the third specific wavelength may be a green wavelength, and similarly, the first specific wavelength is a green wavelength or a blue wavelength, and the second specific wavelength and the third specific wavelength are the remaining two wavelengths different from the green wavelength or the blue wavelength, respectively.
When the first specific wavelength is a red wavelength, the first layer PD31 resonates and absorbs the red light, and then the incident light passes through the first layer PD31, so that the incident light is changed from visible light to incident light with the red light absorbed; when the first specific wavelength is green wavelength, the first layer PD31 performs resonance absorption on red light, and then the incident light passes through the first layer PD31, so that the incident light is changed from visible light into incident light after absorbing green light; when the first specific wavelength is blue wavelength, and the first layer PD31 performs resonance absorption on red light, the incident light passes through the first layer PD31, so that the incident light is changed from visible light to incident light after blue light is absorbed.
Finally, the remaining two lights of the three color lights are subjected to resonance absorption and photoelectric conversion through the second layer PD32, so that the pixel structure can obtain electric signals corresponding to the three colors of lights.
In order to achieve resonant absorption by each PD, in an alternative embodiment, the shape of the light receiving surface of each PD includes any one of: circular, square, triangular, pentagonal, and hexagonal.
That is, the light receiving surface of the PD may have a regular shape, for example, a regular polygon, or may have an irregular shape, and the embodiment of the present application is not particularly limited herein.
The light receiving surface of the PD is in a regular shape, can be in a circular shape, a square shape and the like, and in order to control the resonance wavelength of the light receiving surface of the PD more conveniently, the light receiving surface of the PD is made into a circular shape, and the resonance wavelength of the light receiving surface of the PD is adjusted by adjusting the diameter of the circular shape.
In an alternative embodiment, the volume of each PD is cylindrical;
wherein the light receiving surface of each PD is one of the circular bottom surfaces of the cylinder; the resonance wavelength of the light-receiving surface of each PD has a positive correlation with the diameter of the circular bottom surface.
That is, in order to better enable each PD to generate resonance absorption, in practical applications, a cylindrical structure is adopted in the process, resonance absorption of light is achieved by controlling the diameter of the circular light receiving surface, and when the CIS is manufactured, the distance between PDs inside the pixel structure needs to be controlled, the distance between two adjacent pixel structures needs to be controlled, and the adoption of the circular light receiving surface is also beneficial to more conveniently controlling the distance, and the distance between two adjacent PDs can be better controlled.
For a PD of a circular light receiving surface, the resonance wavelength is the refractive index of the light receiving surface of the PD × the circular diameter + constant, where the constant is one constant related to the structure of the PD.
It can be seen that, in terms of process, it is only necessary to set the circular diameter to enable each PD to achieve the resonance absorption characteristic according to different types of wavelengths, and to prevent crosstalk between adjacent PDs by controlling the pitch.
In order to improve the signal quality of the resulting electrical signal of the pixel structure, in an alternative embodiment,
the diameter of the light receiving face of the PD for resonance absorption of blue light wavelength is 60 nm;
alternatively, the diameter of the light receiving face of the PD for resonance absorption of a red wavelength is 120 nm;
alternatively, the diameter of the light receiving surface of the PD for resonance absorption of the green wavelength is 90 nm.
Here, in practical applications, the circular light receiving surface of the PD is set to 60nm so that the PD can achieve resonance absorption for blue light, the circular light receiving surface of the PD is set to 90nm so that the PD can achieve resonance absorption for green light, and the circular light receiving surface of the PD is set to 120nm so that the PD can achieve resonance absorption for red light.
For example, when the first specific wavelength is a blue wavelength, the diameter of the light receiving surface of the first PD is 60nm, or, when the first specific wavelength is a red wavelength, the diameter of the light receiving surface of the first PD is 120nm, or, when the first specific wavelength is a green wavelength, the diameter of the light receiving surface of the first PD is 90nm, and the diameters of the light receiving surfaces of the second PD and the third PD are similar to the diameter of the light receiving surface of the first PD.
In practical applications, in order to prevent crosstalk between two adjacent PDs, the interval between two adjacent PDs is generally greater than 50nm, where the distance between two PDs is the distance between the centers of circles minus the sum of the radii of the circular light receiving surfaces of the two PDs.
In an alternative embodiment, the pixel structure further comprises a filter disposed on the other side of the first layer PD31, wherein,
the optical filter is used for receiving incident light and transmitting the incident light to the first layer PD 31.
Generally, the pixel structure further includes an optical filter, and since the pixel structure provided in the embodiment of the present application needs to perform resonance absorption and photoelectric conversion on three colors of received visible light, the optical filter included in the pixel structure is used to transmit incident light, that is, visible light, so that the first layer PD31 performs resonance absorption on one of the three colors of visible light, and the second layer PD32 performs resonance absorption on the remaining two colors of the three colors of visible light, so that the pixel structure can obtain electrical signals corresponding to the three colors of light.
For structural compactness, in an alternative embodiment, the second layer PD32 further includes a charge transport circuit, the charge transport circuit being connected to the first layer PD 31; wherein the content of the first and second substances,
The charge transfer circuit is used to transfer the electric signal obtained by the first layer PD31 to the first readout circuit 33.
In addition, in order to place the first readout circuit 33 on the side of the second layer PD32 away from the first layer PD31, a charge transfer circuit is provided on the second layer PD32, wherein the charge transfer circuit is formed by a metal wire, and one end of the metal wire is connected to the first layer PD31 and the other end is connected to the first readout circuit 33 through the metal wire on the first layer PD31, so that the charge transfer circuit transfers the electric signal obtained by the first layer PD31 to the first readout circuit 33, and thus, the first readout circuit 33 and the second readout circuit 34 are both located on the side of the second layer PD32 away from the first layer PD31, so that the pixel structure is more compact, and the pixel structure volume is effectively reduced.
It should be noted that the pixel structures may be arranged in a bayer (bayer) array, and the first layer PD for absorption of a specific wavelength is different between two adjacent pixel structures, for example, the first layer PD of the pixel structure in the first row and the first column of the bayer array is for resonant absorption of red light, the pixel structure in the first row and the second column is for resonant absorption of blue light, the pixel structure in the second row and the second column is for resonant absorption of green light, and the pixel structure in the second row and the second column is for resonant absorption of red light.
In addition, with respect to one PD of the first layer PD, the absorption rate of light of two specific wavelengths can be increased by increasing the thickness of one PD.
The pixel structure according to one or more of the above embodiments is described below by way of example.
Fig. 4 is a schematic structural diagram of an example of an optional optical filter provided in an embodiment of the present application, and as shown in fig. 4, is a schematic structural diagram of optical filters included in four pixel structures arranged in a Bayer array, where W denotes an optical filter of one pixel structure, and each optical filter is an optical filter capable of transmitting visible light, and the optical filter can transmit the visible light to the first layer PD.
Fig. 5A is a schematic structural diagram of an example of an alternative pixel structure provided in an embodiment of the present application, where as shown in fig. 5A, W represents a filter, for transmitting visible light, a plurality of blue cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing blue light) are included in the first layer PD, the first layer PD resonantly absorbs blue light in visible light, and photoelectrically converted into an electric signal, the second layer PD including a plurality of red cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing red light) and a plurality of green cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing green light), the second layer PD resonantly absorbing red and green light in visible light after absorbing blue light, and photoelectrically converted into an electrical signal, so that the first readout circuit can read out an electrical signal corresponding to blue light, and the second readout circuit reads out an electrical signal corresponding to green light and an electrical signal corresponding to red light, respectively.
As shown in fig. 5A, after light passes through the color filter W, first, the blue light passes through a plurality of cylindrical PD arrays, wherein the diameter of the cylindrical PD of the first layer is 60nm, the general cylinder thickness is 80nm-500m, the longer the absorption rate is, the cylinder thickness is preferably larger than 1um for the red light, more than 95% of the blue light is absorbed due to the resonance absorption of the cylindrical PD and converted into an electric signal to be stored in the first layer PD, the readout signal of the B channel is obtained, the red light and the green light are hardly absorbed, and when the light reaches the second layer PD, the rest light is absorbed by the plurality of cylindrical PDs of the second layer, wherein the diameters of the cylindrical PDs are 120nm and 90nm respectively used for absorbing the red light and the green light.
Fig. 5B is a schematic structural diagram of another alternative pixel structure provided in this embodiment of the present application, as shown in fig. 5B, similar to fig. 5A, W denotes a filter, for transmitting visible light, a plurality of red cylindrical PDs (a plurality of cylindrical PDs for resonance absorption of red light) included in the first layer PD, the first layer PD resonance-absorbing blue and green light in visible light, and photoelectrically converted into an electric signal, the second layer PD including therein a plurality of green cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing green light) and a plurality of blue cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing blue light), the second layer PD resonantly absorbing green light and blue light in visible light after absorbing red light, and photoelectrically converted into an electrical signal, so that the first readout circuit can read out an electrical signal corresponding to red light, and the second readout circuit reads out an electrical signal corresponding to blue light and an electrical signal corresponding to green light, respectively.
Fig. 5C is a schematic structural diagram of yet another alternative pixel structure provided in the present application, and as shown in fig. 5C, similar to fig. 5A, W denotes a filter, for transmitting visible light, a plurality of green cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing green light) included in the first layer PD, the first layer PD resonantly absorbing green light in visible light, and photoelectrically converted into an electric signal, the second layer PD including a plurality of red cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing red light) and a plurality of blue cylindrical PDs (a plurality of cylindrical PDs for resonantly absorbing blue light), the second layer PD resonantly absorbing red light and blue light in visible light after absorbing green light, and photoelectrically converted into an electrical signal, so that the first readout circuit can read out an electrical signal corresponding to green light, and the second readout circuit reads out an electrical signal corresponding to red light and an electrical signal corresponding to blue light, respectively.
Fig. 6 is a schematic cross-sectional view of an alternative pixel structure provided in an embodiment of the present application, as shown in fig. 6, which shows a schematic cross-sectional view of two adjacent pixel structures, where a first row and a first column are cross-sectional views of a first layer PD of a first pixel structure, a first row and a second column are cross-sectional views of a second layer PD of the first pixel structure, a second row and a first column are cross-sectional views of the first layer PD of the second pixel structure, a second row and a second column are cross-sectional views of the second layer PD of the second pixel structure, and the first layer PD includes a plurality of blue cylindrical PDs, the first row and the first column are schematic cross-sectional views of the first layer PD, where the blue PDs are arranged, the second layer PD is a plurality of green cylindrical PDs, a plurality of red cylindrical PDs, and a charge transfer circuit of an upper PD, and each row of green cylindrical PDs and each row of red cylindrical PDs are arranged alternately, the charge transfer circuit is usually made of metal, and is disposed on the second layer PD for connecting with the readout circuit, which may also be referred to as a circuit for connecting with the transfer gate, wherein the number of cylindrical PDs is determined by the size of the pixel structure, and it is only necessary to ensure that the interval between adjacent cylindrical PDs is greater than 50 nm.
Taking the second pixel structure as an example, the first layer PD includes a plurality of blue cylindrical PDs, the second row and the first column are schematic cross-sectional views of the first layer PD, the blue cylindrical PDs are arranged, the second layer PD includes a plurality of red cylindrical PDs and a plurality of blue cylindrical PDs (PDs for absorbing blue light wavelengths), each blue cylindrical PD is arranged alternately with each red cylindrical PD, and the number of blue PD cylindrical PDs is the same as that of red cylindrical PDs.
Fig. 7 is a schematic structural diagram of an example of yet another alternative pixel structure provided in an embodiment of the present application, as shown in fig. 7, where a first layer PD is used for resonance absorption of blue light and a second layer PD is used for resonance absorption of red light and green light, and a first readout circuit connected to the first layer PD is shown in fig. 7, and in the first readout circuit of a stacked CIS pixel, V is similar to that of a conventional pixel structureAPPIXThe reset voltage is the power supply voltage of the readout circuit, RST is the reset voltage, SEL is the voltage of the row selection circuit, FD is the voltage read OUT by the photodiode, and OUT is the output voltage; similar to the readout circuit of the conventional pixel structure, the work flow is as follows:
exposure: electron-hole pairs generated by light irradiation are separated by the presence of an electric field generated by the first layer PD, electrons move to the n region, and holes move to the p region; resetting: at the end of exposure, RST is activated, and a read-out area is reset to a high level; reset level readout: after the reset is finished, reading out a reset level, and storing a read-out signal in a first capacitor; and (3) charge transfer: TX is activated, completely transferring charge from the photosensitive region to the n + region for readout; the signal level is read out.
Through the embodiment, based on the sub-wavelength PD, the stacked pixel structure is utilized, so that the false color of a demosaicing process is reduced and the resolution of the CIS is improved compared with a bayer array CIS, meanwhile, the signal-to-noise ratio of the CIS is increased by combining the high signal quantity of the upper layer pixels with the signal of the lower layer pixels, and the power consumption is reduced compared with three layers of stacked pixels.
The embodiment of the application provides a pixel structure, which comprises a first layer PD, a second layer PD, a first readout circuit connected with the first layer PD and a second readout circuit connected with the second layer PD, wherein the first layer PD comprises a PD, the PD is used for performing resonance absorption and photoelectric conversion on light with a corresponding specific wavelength in received incident light to obtain an electric signal corresponding to the light with the specific wavelength, the second layer PD is arranged on one side of the first layer PD and comprises two PDs, the two PDs are respectively used for performing resonance absorption and photoelectric conversion on light with two specific wavelengths in the incident light after the resonance absorption of the first layer PD to obtain electric signals corresponding to the light with the two specific wavelengths, any two PDs in the first layer PD and the second layer PD are different from each other, and the first readout circuit is used for reading out the electric signals corresponding to the light with the specific wavelength respectively, the second reading circuit reads out electric signals corresponding to the two kinds of light with specific wavelengths; that is to say, in the embodiment of the present application, one PD is disposed in the first PD layer, and two PDs different from the one PD are disposed in the second PD layer, so that the pixel structure can perform resonance absorption and photoelectric conversion on incident light in a layered manner, and thus, electrical signals corresponding to light with three specific wavelengths can be obtained, and the problems of high process difficulty, high power consumption and serious crosstalk caused by using a conventional three-layer stacked structure are avoided, so that the quality of signals obtained by the pixel structure is improved, and the imaging quality of the CIS is improved.
Example two
Fig. 8 is a schematic structural diagram of an alternative CIS provided in an embodiment of the present application, and as shown in fig. 8, an embodiment of the present application provides a CIS800, where the CIS800 includes a pixel structure described in one or more embodiments above.
Fig. 9 is a schematic structural diagram of an alternative terminal provided in an embodiment of the present application, and as shown in fig. 9, an embodiment of the present application provides a terminal 900, where the terminal 900 includes the CIS described in the above embodiment.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application.
Claims (10)
1. A pixel structure comprising a first layer of Photodiodes (PD), a second layer of PDs, a first readout circuitry connected to the first layer of PDs and a second readout circuitry connected to the second layer of PDs; wherein the content of the first and second substances,
The first layer PD comprises a PD, and the PD is used for performing resonance absorption and photoelectric conversion on light with a corresponding specific wavelength in received incident light to obtain an electric signal corresponding to the light with the specific wavelength;
the second layer PD is arranged on one side of the first layer PD, and comprises two PDs which are used for performing resonance absorption and photoelectric conversion on two kinds of light with specific wavelengths which correspond to each other in incident light subjected to resonance absorption by the first layer PD to obtain electric signals corresponding to the two kinds of light with specific wavelengths;
the first readout circuit reads out an electric signal corresponding to the light of the specific wavelength;
the second reading circuit respectively reads the electric signals corresponding to the two lights with the specific wavelengths;
wherein any two PDs in the first layer PD and the second layer PD are different from each other;
wherein the number of the one PD is at least two, and the number of each PD of the two PDs is at least two;
wherein the areas of the light receiving faces of any two kinds of PDs of the first layer PD and the second layer PD are different.
2. The pixel structure according to claim 1, wherein when the first layer PD comprises a first type PD, the second layer PD comprises a second type PD and a third type PD;
The first PD is used for carrying out resonance absorption on light with a first specific wavelength in the received incident light according to the resonance wavelength of a light receiving surface of the first PD, and carrying out photoelectric conversion on the absorbed light to obtain an electric signal corresponding to the light with the first specific wavelength;
the second PD is used for performing resonance absorption on light with a second specific wavelength in the received incident light subjected to resonance absorption by the first layer PD according to the resonance wavelength of the light receiving surface of the second PD, and performing photoelectric conversion on the absorbed light to obtain an electric signal corresponding to the light with the second specific wavelength;
the third PD is configured to perform resonance absorption on light with a third specific wavelength in the received incident light subjected to resonance absorption by the first layer PD according to a resonance wavelength of a light receiving surface of the third PD, and perform photoelectric conversion on the absorbed light to obtain an electrical signal corresponding to the light with the third specific wavelength;
the first readout circuit reads out an electric signal corresponding to the light with the first specific wavelength;
the second readout circuit reads out the electrical signal corresponding to the light with the second specific wavelength and the electrical signal corresponding to the light with the third specific wavelength respectively;
Wherein a resonance wavelength of a light receiving face of each of the first, second, and third PDs is a wavelength at which the light receiving face of the each PD undergoes resonance absorption.
3. The pixel structure according to claim 2, wherein the first specific wavelength, the second specific wavelength and the third specific wavelength comprise:
any one combination of the following three wavelengths: red, green, blue wavelengths.
4. The pixel structure of claim 2, wherein the shape of the light receiving face of each PD comprises any one of: circular, square, triangular, pentagonal, and hexagonal.
5. The pixel structure of claim 4, wherein the volume of each PD is a cylinder;
wherein the light receiving surface of each PD is one of the circular bottom surfaces of the cylinder; the resonance wavelength of the light receiving surface of each PD has a positive correlation with the diameter of the circular bottom surface.
6. The pixel structure of claim 5,
the diameter of the light receiving face of the PD for resonance absorption of blue light wavelength is 60 nm;
alternatively, the diameter of the light receiving face of the PD for resonance absorption of a red wavelength is 120 nm;
Alternatively, the diameter of the light receiving face of the PD for resonance absorption of the green wavelength is 90 nm.
7. The pixel structure of claim 1, further comprising a filter disposed on another side of the first layer PD, wherein,
the optical filter is used for receiving the incident light and transmitting the incident light to the first layer PD.
8. The pixel structure according to claim 1, wherein the second layer PD further comprises a charge transfer circuit connected to the first layer PD; wherein, the first and the second end of the pipe are connected with each other,
the charge transfer circuit is configured to transfer the electrical signal obtained by the first layer PD to the first readout circuit.
9. A cmos image sensor CIS, characterized in that it comprises a pixel structure according to any one of the preceding claims 1 to 8.
10. A terminal characterized in that it comprises a CIS as claimed in claim 9 above.
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