CN111769126A - Photosensitive pixel module, image sensor and electronic device - Google Patents

Photosensitive pixel module, image sensor and electronic device Download PDF

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Publication number
CN111769126A
CN111769126A CN202010548644.XA CN202010548644A CN111769126A CN 111769126 A CN111769126 A CN 111769126A CN 202010548644 A CN202010548644 A CN 202010548644A CN 111769126 A CN111769126 A CN 111769126A
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layer
photosensitive pixel
light
cathode
avalanche
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张学勇
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Guangdong Oppo Mobile Telecommunications Corp Ltd
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Guangdong Oppo Mobile Telecommunications Corp Ltd
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Priority to PCT/CN2021/088659 priority patent/WO2021253971A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14618—Containers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H01L27/14627—Microlenses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1463—Pixel isolation structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14634—Assemblies, i.e. Hybrid structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14636—Interconnect structures

Abstract

The present disclosure relates to a photosensitive pixel module, an image sensor and an electronic device, the photosensitive pixel module including: the device comprises a protection ring, a plurality of photosensitive pixel units and shallow groove isolation, wherein the photosensitive pixel units are arranged in the protection ring; the shallow slot isolation is arranged between any two adjacent photosensitive pixel units in the plurality of photosensitive pixel units. The plurality of photosensitive pixel units are arranged in the protective ring, and shallow groove isolation is arranged between any two adjacent photosensitive pixel units in the plurality of photosensitive pixel units for isolation, so that photoelectric conversion can be realized, the plurality of photosensitive pixel units share the protective ring, the occupied area of the protective ring is reduced, the occupation ratio and the filling factor of the photosensitive pixel units in a unit area are increased, and the improvement of the photon sensitivity and the imaging quality of the image sensor is facilitated.

Description

Photosensitive pixel module, image sensor and electronic device
Technical Field
The present disclosure relates to the field of electronic devices, and in particular, to a photosensitive pixel module, an image sensor, and an electronic device.
Background
In image sensors, light signals are generally converted into electrical signals by photosensitive pixel cells, and a plurality of photosensitive pixel cells are distributed in an array in the image sensor. Generally, the higher the area fraction of photosensitive pixel cells per unit area of an image sensor, the higher the quality of the image formed by the image sensor. At present, due to the problems of the structure of a pixel sensing unit and the like, the area occupation ratio of a photosensitive pixel unit in a unit area in an image sensor is low, and the improvement of imaging quality is not facilitated.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
The present disclosure is directed to a photosensitive pixel module, an image sensor and an electronic device, so as to increase an area ratio of a photosensitive pixel unit in a unit area of the image sensor at least to a certain extent.
According to a first aspect of the present disclosure, there is provided a photosensitive pixel module including:
a guard ring;
a plurality of light-sensitive pixel units arranged in the protective ring;
the shallow slot isolation is arranged between any two adjacent photosensitive pixel units in the plurality of photosensitive pixel units.
According to a second aspect of the present disclosure, there is provided an image sensor including the above-described photosensitive pixel module.
According to a third aspect of the present disclosure, there is provided an electronic device including the image sensor described above.
The photosensitive pixel module provided by the embodiment of the disclosure sets a plurality of photosensitive pixel units in the protection ring, and a shallow slot is arranged between any two adjacent photosensitive pixel units in the plurality of photosensitive pixel units for isolation, so that photoelectric conversion can be realized, and because the plurality of photosensitive pixel units share the protection ring, the occupied area of the protection ring is reduced, the occupation ratio and the filling factor of the photosensitive pixel units in a unit area are increased, and the improvement of the photon sensitivity and the imaging quality of the image sensor is facilitated.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.
Fig. 1 is a schematic structural diagram of a first photosensitive pixel module according to an exemplary embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a second type of photosensitive pixel module provided in an exemplary embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a third photosensitive pixel module according to an exemplary embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a fourth photosensitive pixel module according to an exemplary embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of a fifth photosensitive pixel module according to an exemplary embodiment of the present disclosure;
fig. 6 is a schematic structural diagram of a sixth photosensitive pixel module according to an exemplary embodiment of the present disclosure;
fig. 7 is a schematic diagram illustrating an interval between light-sensing pixel units in a light-sensing pixel module according to an exemplary embodiment of the present disclosure;
fig. 8 is a schematic structural diagram of an image sensor according to an exemplary embodiment of the present disclosure;
fig. 9 is a schematic structural diagram of an electronic device according to an exemplary embodiment of the present disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted.
Although relative terms, such as "upper" and "lower," may be used in this specification to describe one element of an icon relative to another, these terms are used in this specification for convenience only, e.g., in accordance with the orientation of the examples described in the figures. It will be appreciated that if the device of the icon were turned upside down, the element described as "upper" would become the element "lower". When a structure is "on" another structure, it may mean that the structure is integrally formed with the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure via another structure.
The terms "a," "an," "the," and "said" are used to indicate the presence of one or more elements/components/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.
First, in the present exemplary embodiment, there is provided a photosensitive pixel module 100, as shown in fig. 1, the photosensitive pixel module 100 including: a guard ring 110, a plurality of light-sensitive pixel cells 120, and a Shallow Trench Isolation (STI) 130, the plurality of light-sensitive pixel cells 120 being arranged within the guard ring 110; shallow trench isolations 130 are provided between any two adjacent ones of the plurality of light-sensitive pixel cells 120 within the same guard ring 110.
The photosensitive pixel module 100 provided by the embodiment of the present disclosure can implement photoelectric conversion by disposing the plurality of photosensitive pixel units 120 in the protection ring 110, and disposing the shallow trench isolations 130 between any two adjacent photosensitive pixel units 120 in the plurality of photosensitive pixel units 120 for isolation, and since the plurality of photosensitive pixel units 120 share the protection ring 110, the area occupied by the protection ring 110 is reduced, the ratio and the fill factor of the photosensitive pixel units 120 in a unit area are increased, which is beneficial to improving the imaging quality of the image sensor.
Portions of the light-sensing pixel module 100 provided by the embodiments of the present disclosure will be described in detail below:
the light-sensitive pixel cell 120 may comprise a Single-photon avalanche diode (SPAD), which is a photodiode operating at large reverse bias voltages, essentially a PN junction. When the device works normally, reverse bias voltage (-15V to-30V) larger than avalanche breakdown is applied to two ends of the PN junction. Since the PN junction is reverse biased, no current flows. But when only a single photon enters the PN junction depletion region, a photogenerated carrier is triggered. The photogenerated carriers continue to impact and excite other carriers in the PN junction under the action of an electric field formed by large bias voltage to generate large current. The whole process resembles an avalanche. And are therefore called single photon avalanche diodes. The single-photon avalanche diode is mainly applied to dToF, is a key device for measuring single photon in dToF (Direct-time of flight), and is also the most basic device of a pixel.
On this basis, as shown in fig. 2, the light-sensitive pixel unit 120 includes: the substrate comprises a substrate 122, an avalanche layer 121, a cathode diffusion layer 124 and a cathode layer 123, wherein the substrate 122 is provided with an anode region 1221, the substrate 122 is provided with a first accommodating part 1222, the first accommodating part 1222 is positioned at one side of the anode region 1221, and one side of the first accommodating part 1222 far away from the anode region 1221 is provided with a first opening 1223 (the opening is positioned at one surface of the substrate); the avalanche layer 121 is provided in the first accommodating portion 1222 of the substrate 122; the cathode layer 123 is disposed on the avalanche layer 121, and the cathode layer 123 is disposed on a side of the avalanche layer 121 away from the anode region 1221, and the cathode layer 123 is exposed to the first opening 1223 of the first receiving portion 1222; the cathode diffusion layer 124 is provided between the avalanche layer 121 and the cathode layer 123. Shallow trench isolations 130 are provided between the cathode diffusions 124 of two adjacent photosensitive pixel cells 120. Wherein the first receiving portion 1222 may be a cavity having a first opening 1223.
The avalanche photodiode with an n +/p-well structure is provided in the embodiments of the present disclosure, which is only an exemplary illustration, and the photosensitive pixel module provided in the embodiments of the present disclosure may also be used in avalanche photodiodes with other n +/p-well structures, and the embodiments of the present disclosure are not limited thereto.
By further providing a cathode diffusion layer 124 between the cathode layer 123 and the avalanche layer 121, the avalanche layer 121 is moved from the surface of the cathode layer 123 into a region remote from the surface, thus enabling the avalanche region to be remote from the shallow trench isolation 130. Due to the Si-SiO at the interface of the shallow trench isolation 1302Has a large number of trap energy levels capable of trapping carrier currentThe electron, which results in a strong electric field in the avalanche layer 121, and if the trapped carriers are very close to the avalanche layer 121, they will easily enter the avalanche layer 121 to initiate avalanche ionization, which causes device false breakdown, and as a final result, the DCR (Dark count rate) of the device is too large, and the above problem can be solved by the cathode diffusion layer 124.
As an example, a stepped hole, which may be a stepped square hole or a stepped circular hole, is provided on the substrate 122. The avalanche layer 121 may be disposed at the bottom of the step hole, where the step hole is a blind hole, and the bottom of the step hole refers to an end of the step hole away from the first opening 1223. The cathode diffusion layer 124 is disposed on a side of the avalanche layer 121 away from the bottom of the step hole, and a side of the cathode diffusion layer 124 away from the avalanche layer 121 may be exposed to the first opening 1223 of the step hole. The cathode layer 123 is embedded in the cathode diffusion layer 124, and the cathode layer 123 is exposed to a surface of the cathode diffusion layer 124 remote from the avalanche layer 121. In the surface where the avalanche layer 121 and the cathode diffusion layer 124 contact each other, the area of the contact surface of the cathode diffusion layer 124 is larger than the area of the contact surface of the avalanche layer 121. As shown in fig. 3, the side of the first opening 1223 of the stepped hole in the substrate 122 may extend to be flush with the surface of the cathode layer 123 remote from the avalanche layer 121. Alternatively, as shown in fig. 2, the side of the substrate 122 where the first opening 1223 of the step hole is located may extend to the bottom end of the shallow trench isolation 130. The bottom end of the shallow trench isolation 130 refers to the end of the shallow trench isolation 130 that is embedded in the substrate 122. The top end face of the shallow trench isolation 130 is flush with the top end face of the cathode diffusion layer 124.
The depth of the shallow trench isolation 130 is greater than the depth of the cathode layer 123, and the depth of the shallow trench isolation 130 is less than the depth of the cathode diffusion layer 124. Here, the depth refers to a distance of each device in a direction from the cathode layer 123 to the avalanche layer 121. The depth of the shallow trench isolation 130 may be 1 to 3 microns.
The shallow trench isolation 130 may be formed by depositing, patterning, and etching silicon through a silicon nitride mask and filling the trench with a deposited oxide. In forming the shallow trench isolation 130, a silicon nitride layer may be deposited on the semiconductor substrate 122 first, and then the silicon nitride layer may be patterned to form a hard mask; then, the substrate 122 is etched to form a trench between the adjacent cathode diffusion layers 124; finally, the trench is filled with oxide to form the shallow trench isolation 130. As an example, the shallow trench isolation 130 may have a trapezoidal cross-sectional shape and the filled oxide may be silicon dioxide.
The cathode layer 123 and the cathode diffusion layer 124 are doped with a first type of dopant and the avalanche layer 121 and the substrate 122 are doped with a second type of dopant. Illustratively, the cathode layer 123 may be a heavily n-doped semiconductor layer (e.g., a heavily n-doped silicon layer). The cathode diffusion layer 124 may be an n-type doped semiconductor layer (such as n-type silicon) with a doping concentration less than that of the cathode layer 123. The avalanche layer 121 may be a heavily p-doped semiconductor layer (such as a heavily p-doped silicon layer). The substrate 122 may be a semiconductor layer (such as p-type silicon) that may be p-doped with a doping concentration less than that of the avalanche layer 121.
In the embodiment of the disclosure, an n +/p-well type pn junction design is adopted, electron ionization is mainly used during n +/p-well avalanche breakdown, and the electron mobility is about 3 times higher than the hole mobility, so that the electron ionization is easier than the hole ionization. The sensitivity of the image sensor is improved, namely the photon detection efficiency is higher. The p-type substrate 122 is adopted, the p-type substrate 122 is usually selected in a CMOS process, firstly, an integrated circuit tends to mainly adopt an NMOS transistor, and the NMOS transistor is electron-conductive, so that the electron mobility is about 3 times of the hole mobility in the PMOS transistor under the same condition; secondly, the p-type substrate 122 can be directly used as an NMOS transistor, and the p-type silicon substrate 122 can be directly grounded, so that the bias voltage of the image sensor during operation can be reduced, and the noise signal can be stably reduced.
The light-sensing pixel module 100 provided by the embodiment of the present disclosure may be used in a BSI (Backside-illuminated) image sensor. The BSI technique may employ an n +/p-well technique, with the avalanche region being generated primarily in the p-well by electron ionization. The electron ionization probability is about 3 times higher than the hole ionization probability. The n +/p-well in the BSI image sensor adopts electron avalanche ionization, the ionization rate is high, and the photon detection efficiency PDE is high.
On this basis, as shown in fig. 4, the photosensitive pixel module 100 provided by the embodiment of the disclosure may further include a signal collection layer 140, a color film layer 160, and a light convergence layer 150, where the pixel collection layer is stacked on one side of the photosensitive pixel unit 120 away from the light entrance side, the signal collection layer 140 includes a signal collection circuit, and the signal collection circuit is connected to the photosensitive pixel unit 120. The color film layer 160 is disposed on the light-incident side of the light-sensing pixel unit 120. The light converging layer 150 is disposed on the light incident side of the light-sensitive pixel unit 120, and the light converging layer 150 is used for converging light rays on the light-sensitive pixel unit 120.
The light-entering side of the photosensitive pixel unit 120 may be a side of the substrate 122 away from the cathode layer 123, and the signal acquisition layer 140 is disposed on a side of the photosensitive pixel unit 120 away from the light-entering side, that is, light can directly enter the photosensitive pixel unit 120. A single photon avalanche diode in the light-sensitive pixel cell 120 generates an avalanche current under illumination. Signal acquisition circuitry in the signal acquisition layer 140 receives the avalanche current and transmits the avalanche current to the processor.
The signal acquisition circuit can acquire the avalanche signal in a line-by-line scanning mode. A plurality of rows of circuit cells are disposed in the signal acquisition circuit layer, each circuit cell being connected to a light-sensitive pixel cell 120. The circuit units are scanned line by line while the signals are collected, and the photoelectric signals of the photosensitive pixel units 120 are acquired line by line.
The color film layer 160 may include a plurality of color light transmission units, such as RGB light transmission units. The RGB light-transmitting units are distributed in a staggered manner. Each light-sensitive pixel cell 120 corresponds to a light-transmissive cell, and illustratively, any R light-transmissive cell is located above a pixel sensor cell, any G light-transmissive cell is located above a pixel sensor cell, and any B light-transmissive cell is located above a pixel sensor cell.
The light converging layer 150 may be disposed on a side of the color film layer 160 away from the photosensitive pixel unit 120, and the light converging layer 150 may include an anti-reflection film layer and a micro-lens array. The anti-reflection film layer is disposed on a side of the color film layer 160 away from the photosensitive pixel unit 120, and the micro-lens array is disposed on a side of the anti-reflection film layer away from the color film layer 160. Ambient light enters the light-sensitive pixel cell 120 after passing through the microlens array, the anti-reflection film layer, and the color film layer 160. Incident light is converged in the ionization region of the corresponding avalanche layer 121 by using the micro-lens, and reflected light is reduced by the anti-reflection film layer, so that the photon detection efficiency PDE of the device can be improved. Of course, in practical applications, the photosensitive pixel module 100 provided in the embodiment of the disclosure may also improve the device photon detection efficiency PDE in other ways, which is not specifically limited in the embodiment of the disclosure.
Alternatively, as shown in fig. 5, a light-sensing pixel unit 120 provided by the embodiment of the present disclosure may include: the cathode layer 123 is arranged on the substrate 122, the cathode layer 123 is provided with a second accommodating part 1231, and the second accommodating part 1231 is provided with a second opening 1232 at one side far away from the substrate 122; the avalanche layer 121 is embedded on the side of the cathode layer 123 away from the substrate 122, and the avalanche layer 121 is exposed to the second opening 1232 of the cathode layer 123; the anode layer 125 is provided on the side of the avalanche layer 121 remote from the substrate 122. The anode layer 125 may be embedded on a side of the avalanche layer 121 away from the cathode layer 123. The second locus 1231 may be a cavity having a second opening 1232.
The avalanche photodiode with a p +/n-well structure is provided in the embodiments of the present disclosure, which is only an exemplary illustration, and the photosensitive pixel module provided in the embodiments of the present disclosure may also be used in avalanche photodiodes with other p +/n-well structures, and the embodiments of the present disclosure are not limited thereto.
On this basis, the cathode layer 123 comprises dopants of the first type, the avalanche layer 121, the anode layer 125 and the substrate 122 comprise dopants of the second type, and the doping concentration of the avalanche layer 121 is smaller than the doping concentration of the anode layer. Illustratively, the cathode layer 123 may be a heavily n-doped semiconductor layer, the cathode layer 123 forming an n-well. Anode layer 125 may be a heavily p-doped semiconductor layer and avalanche layer 121 may be a p-doped semiconductor, with avalanche layer 121 having a lower doping concentration than the anode layer.
The avalanche layers 121 in any two adjacent photosensitive pixel cells 120 in the plurality of photosensitive pixel cells 120 in the same guard ring 110 are isolated by shallow trench isolations 130, and the depth of the shallow trench isolations 130 is greater than the depth of the anode layer and less than the depth of the avalanche layers 121.
The light-sensing pixel cell 120 may be used for a Front-illuminated (FSI) image sensor. As shown in fig. 6, the light-sensing pixel module 100 further includes: the light-sensitive pixel unit comprises a signal acquisition layer 140, a color film layer 160 and a light convergence layer 150, wherein the pixel acquisition layer is stacked on the light inlet side of the light-sensitive pixel unit 120, the signal acquisition layer 140 comprises a signal acquisition circuit, and the signal acquisition circuit is connected with the light-sensitive pixel unit 120. The color film layer 160 is disposed on a side of the signal acquisition layer 140 away from the photosensitive pixel unit 120. The light converging layer 150 is disposed on the light incident side of the light-sensitive pixel unit 120, and the light converging layer 150 is used for converging light rays on the light-sensitive pixel unit 120. In the FSI image sensor, light enters the photosensitive pixel unit 120 after passing through the signal acquisition layer 140, so the color film layer 160 and the light converging layer 150 are located on the side of the signal acquisition layer 140 away from the photosensitive pixel unit 120.
The signal acquisition circuit can acquire the avalanche signal in a line-by-line scanning mode. A plurality of rows of circuit cells are disposed in the signal acquisition circuit layer, each circuit cell being connected to a light-sensitive pixel cell 120. The circuit units are scanned line by line while the signals are collected, and the photoelectric signals of the photosensitive pixel units 120 are acquired line by line.
The color film layer 160 may include a plurality of color light transmission units, such as RGB light transmission units. The RGB light-transmitting units are distributed in a staggered manner. Each light-sensitive pixel cell 120 corresponds to a light-transmissive cell, and illustratively, any R light-transmissive cell is located above a pixel sensor cell, any G light-transmissive cell is located above a pixel sensor cell, and any B light-transmissive cell is located above a pixel sensor cell.
The light converging layer 150 may be disposed on a side of the color film layer 160 away from the photosensitive pixel unit 120, and the light converging layer 150 may include an anti-reflection film layer and a micro-lens array. The anti-reflection film layer is disposed on a side of the color film layer 160 away from the photosensitive pixel unit 120, and the micro-lens array is disposed on a side of the anti-reflection film layer away from the color film layer 160. Ambient light enters the light-sensitive pixel cell 120 after passing through the microlens array, the anti-reflection film layer, and the color film layer 160. Incident light is converged in the ionization region of the corresponding avalanche layer 121 by using the micro-lens, and reflected light is reduced by the anti-reflection film layer, so that the photon detection efficiency PDE of the device can be improved. Of course, in practical applications, the photosensitive pixel module 100 provided in the embodiment of the disclosure may also improve the device photon detection efficiency PDE in other ways, which is not specifically limited in the embodiment of the disclosure.
As shown in fig. 2, the guard ring 110 may include Deep trench isolations 111 (DTI), the Deep trench isolations 111 having a closed ring shape, and the Deep trench isolations 111 surrounding the plurality of light-sensitive pixel cells 120. The deep trench isolation 111 may be formed by reactive ion etching a U-shaped trench in the substrate 122 and then filling the U-shaped trench with a conductive material to form the deep trench isolation 111.
It should be noted that in the fabrication process of the plurality of photosensitive pixel cells 120 in the embodiment of the present disclosure, the substrate 122 may be a whole substrate 122, and the avalanche layer 121, the cathode layer 123, and the like may be formed in the substrate 122 by forming a hole in the substrate 122.
Alternatively, as shown in fig. 5, the guard ring 110 may include a semiconductor guard ring 112, the semiconductor guard ring 112 being provided on the cathode layer 123, and the semiconductor guard ring 112 having a closed ring shape. The material of the semiconductor guard ring 112 may be a semiconductor ring of a different doping concentration than the other layers. For example, a heavily doped semiconductor ring (p-type heavily doped) may be provided on the substrate 122. Alternatively, the n-type semiconductor guard ring 112 can be disposed on the substrate 122, where the n-type semiconductor guard ring 112 has a doping concentration less than the cathode layer 123. Of course, in practical applications, the protection ring 110 provided in the embodiment of the present disclosure may also be made of other materials, and the embodiment of the present disclosure is not particularly limited thereto.
When the guard ring 110 includes the semiconductor guard ring 112, a deep trench isolation 170 having a trapezoidal cross-section may be provided outside the annular semiconductor guard ring 112. The deep trench isolation 170 can prevent adjacent pixel area optical cross-talk, prevent carrier electrical cross-talk, and can improve the light collection efficiency of the light-sensitive pixel cells 120 within the guard ring 110.
In the disclosed embodiment, a plurality of light-sensitive pixel cells 120 may be disposed within one guard ring 110, and any two adjacent light-sensitive pixel cells 120 of the plurality of light-sensitive pixel cells 120 are separated by a shallow trench isolation 130. Illustratively, the light-sensing pixel unit 120 may be a rectangular parallelepiped light-sensing pixel unit 120, in which case the guard ring 110 may be a rectangular frame shape. The plurality of photosensitive pixel cells 120 may be distributed in an array within the guard ring 110, for example, the number of pixel sensing cells within one guard ring 110 may be 2, 3, 4, 5 … 16, etc., and the distribution of the photosensitive pixel cells 120 within the guard ring 110 may be 1 × 2, 1 × 3, 2 × 2, 1 × 5 … 4 × 4, etc. Of course, in practical applications, the number of the photosensitive pixel units 120 in one guard ring 110 may be other numbers, and the arrangement manner thereof may also be other manners, which is not limited by the embodiments of the disclosure.
Typically, to reduce premature pixel sensor cell breakdown, guard ring 110 has a width of at least 1 micron and the process requires a minimum isolation well of at least 0.5 micron. The effective photosensitive pixel cell 120 distance needs to be at least 2.5 microns. In the related art, each pixel needs to be surrounded by a guard ring 110 structure. The minimum distance between the pixel avalanche layer 121 and the guard ring 110 is limited by the technological process, the minimum distance between the avalanche layer 121 and the guard ring 110 is 1 micron, and the width of the guard ring 110 is not less than 0.5 micron. This directly results in an image sensor with a pixel pitch (pixel pitch) of less than 5 microns and a fill factor FF of less than 20%. As shown in fig. 7, in the embodiment of the present disclosure, shallow trench isolation 130 is used for isolation, and the minimum distance between the photosensitive pixel unit 120 and the photosensitive pixel unit 120 is 2La + LDTIIs reduced to L by more than or equal to 2.5 micronsSTIBy the shallow trench isolation 130 and the common guard ring 110, the spacing of adjacent pixels can be reduced to 1 micron.
The photosensitive pixel module 100 provided by the embodiment of the present disclosure is suitable for visible light to near infrared light of any wavelength, but considering that 940nm laser light sources are adopted in current similar time-of-flight sensors to avoid interference of solar background light, the thickness of the silicon wafer of the photosensitive pixel module 100 can be controlled to be about 10 micrometers to 3 micrometers, because the penetration depth of the 940nm laser light sources in the silicon wafer is about 10 micrometers. Here, the thickness of the light-sensing pixel module 100 refers to a dimension from a surface under the cathode layer 123 to an upper surface of the anode layer.
The photosensitive pixel module 100 provided by the embodiment of the present disclosure can implement photoelectric conversion by disposing the plurality of photosensitive pixel units 120 in the protection ring 110, and disposing the shallow trench isolations 130 between any two adjacent photosensitive pixel units 120 in the plurality of photosensitive pixel units 120 for isolation, and since the plurality of photosensitive pixel units 120 share the protection ring 110, the area occupied by the protection ring 110 is reduced, the occupation ratio of the photosensitive pixel units 120 in a unit area is increased, and the improvement of the imaging quality of the image sensor is facilitated.
The present exemplary embodiment also provides an image sensor 010, which includes the above-described light-sensing pixel module 100, as shown in fig. 8.
A plurality of light-sensing pixel modules 100 may be included in the image sensor, and the plurality of light-sensing pixel modules 100 are distributed in an array. In fabricating the image sensor, the layers of photosensitive pixel cells 120 may be fabricated separately from the signal acquisition layer 140, and then the layers of photosensitive cells and the signal acquisition layer 140 may be stacked by a 3D stacking technique.
On one hand, the layer of the photosensitive pixel unit 120 and the signal acquisition layer 140 can be processed separately by 3D stacking in process technology, and different process nodes can be adopted, which is beneficial to flexible design and power consumption control of the signal acquisition layer 140 (read circuit). In the process, the current mainstream CIS chips are all stacked by BSI + 3D. On the other hand, in terms of power consumption, the 3D stacking process can adopt different process procedures for the pixel unit layer and the signal acquisition layer 140, and particularly, the signal acquisition layer 140 is manufactured by adopting a relatively advanced small process, so that power consumption can be greatly saved. One-half of the power consumption can be expected to be saved.
The image sensor provided by the embodiment of the present disclosure includes a photosensitive pixel module 100, a plurality of photosensitive pixel units 120 are disposed in a protection ring 110, and a shallow trench isolation 130 is disposed between any two adjacent photosensitive pixel units 120 in the plurality of photosensitive pixel units 120 for isolation, so that photoelectric conversion can be achieved, and since the plurality of photosensitive pixel units 120 share the protection ring 110, the area occupied by the protection ring 110 is reduced, the occupation ratio and the filling factor of the photosensitive pixel units 120 in a unit area are increased, and the image quality of the image sensor is improved.
The exemplary embodiments of the present disclosure also provide an electronic device including the image sensor 010 described above.
The image sensor 010 provided by the embodiment of the disclosure can be used for a camera module of an electronic device, and functions of photographing and recording of the electronic device are realized. The camera module of the electronic device can further comprise a lens, and the lens is used for transmitting external light to the image sensor. Or the image sensor may be used for 3D ranging of electronic devices, such as range finding in augmented reality devices or mixed reality devices.
As shown in fig. 9, the electronic device 100 provided in the embodiment of the present disclosure further includes a display screen 10, a bezel 20, a main board 30, a battery 40, and a rear cover 50. The display screen 10 is mounted on the frame 20 to form a display surface of the electronic device, and the display screen 10 serves as a front shell of the electronic device 100. The rear cover 50 is adhered to the frame by double-sided adhesive, and the display screen 10, the frame 20 and the rear cover 50 form a receiving space for receiving other electronic components or functional modules of the electronic device 100. Meanwhile, the display screen 10 forms a display surface of the electronic apparatus 100 for displaying information such as images, texts, and the like. The Display screen 10 may be a Liquid Crystal Display (LCD) or an organic light-Emitting Diode (OLED) Display screen.
A glass cover may be provided over the display screen 10. Wherein, the glass cover plate can cover the display screen 10 to protect the display screen 10 and prevent the display screen 10 from being scratched or damaged by water.
The display screen 10 may include a display area 11 and a non-display area 12. The display area 11 performs a display function of the display screen 10 for displaying information such as images and texts. The non-display area 12 does not display information. The non-display area 12 may be used to set functional modules such as a camera, a receiver, a proximity sensor, and the like. In some embodiments, the non-display area 12 may include at least one area located at upper and lower portions of the display area 11.
The display screen 10 may be a full-face screen. At this time, the display screen 10 may display information in a full screen, so that the electronic apparatus 100 has a large screen occupation ratio. The display screen 10 comprises only the display area 11 and no non-display area. At this time, functional modules such as a camera and a proximity sensor in the electronic apparatus 100 may be hidden under the display screen 10, and the fingerprint identification module of the electronic apparatus 100 may be disposed on the back of the electronic apparatus 100.
The bezel 20 may be a hollow frame structure. The material of the frame 20 may include metal or plastic. The main board 30 is mounted inside the receiving space. For example, the main board 30 may be mounted on the frame 20 and accommodated in the accommodating space together with the frame 20. The main board 30 is provided with a grounding point to realize grounding of the main board 30. One or more of the functional modules such as a motor, a microphone, a speaker, a receiver, an earphone interface, a universal serial bus interface (USB interface), a camera, a proximity sensor, an ambient light sensor, a gyroscope, and a processor may be integrated on the main board 30. Meanwhile, the display screen 10 may be electrically connected to the main board 30.
The main board 30 is provided with a display control circuit. The display control circuit outputs an electric signal to the display screen 10 to control the display screen 10 to display information.
The battery 40 is mounted inside the receiving space. For example, the battery 40 may be mounted on the frame 20 and be accommodated in the accommodating space together with the frame 20. The battery 40 may be electrically connected to the motherboard 30 to enable the battery 40 to power the electronic device 100. The main board 30 may be provided with a power management circuit. The power management circuit is used to distribute the voltage provided by the battery 40 to the various electronic components in the electronic device 100.
The rear cover 50 is used to form an outer contour of the electronic device 100. The rear cover 50 may be integrally formed. In the forming process of the rear cover 50, a rear camera hole, a fingerprint identification module mounting hole and the like can be formed in the rear cover 50.
The lens may be located in a rear camera hole on the rear cover 50, and the image sensor 010 may be located in a middle frame, a rear cover, or a main board. The image sensor 010 may be connected to an image processor on the motherboard for transmitting the optical and electrical signals to the motherboard.
The electronic device provided by the embodiment of the disclosure includes an image sensor 010, a plurality of photosensitive pixel units 120 are arranged in a protection ring 110, and a shallow trench isolation 130 is arranged between any two adjacent photosensitive pixel units 120 in the plurality of photosensitive pixel units 120 for isolation, so that photoelectric conversion can be realized, and since the plurality of photosensitive pixel units 120 share the protection ring 110, the area occupied by the protection ring 110 is reduced, the occupation ratio of the photosensitive pixel units 120 in a unit area is increased, and the improvement of the imaging quality of the image sensor is facilitated.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims (19)

1. A photosensitive pixel module, comprising:
a guard ring;
a plurality of light-sensitive pixel units arranged in the protective ring;
the shallow slot isolation is arranged between any two adjacent photosensitive pixel units in the plurality of photosensitive pixel units.
2. A photosensitive pixel module according to claim 1, wherein the photosensitive pixel cell comprises:
the substrate is provided with an anode area, a first accommodating part is arranged on the substrate and located on one side of the anode area, and a first opening is formed in one side, away from the anode area, of the first accommodating part;
an avalanche layer provided in the first accommodating portion of the substrate;
a cathode layer disposed on the avalanche layer, wherein the cathode layer is on a side of the avalanche layer away from the anode region, and the cathode layer is exposed to the first opening.
3. A photosensitive pixel module according to claim 2, wherein the photosensitive pixel cell further comprises:
a cathode diffusion layer disposed between the avalanche layer and the cathode layer.
4. A photosensitive pixel module according to claim 3, wherein a depth of the shallow trench isolation is greater than a depth of the cathode layer, and the depth of the shallow trench isolation is less than a depth of the cathode diffusion layer.
5. A photosensitive pixel module as defined in claim 3, wherein the cathode layer is embedded in the cathode diffusion layer, and a side of the cathode layer remote from the avalanche layer is exposed to the cathode diffusion layer.
6. A photosensitive pixel module according to claim 5, wherein the shallow trench isolation is provided between cathode diffusion layers of two adjacent photosensitive pixel cells.
7. A light-sensitive pixel module as defined in claim 3, wherein the cathode layer and the cathode diffusion layer are doped with a first type of dopant, and the avalanche layer and the substrate are doped with a second type of dopant.
8. A photosensitive pixel module as defined in claim 7, wherein a doping concentration of said cathode layer is greater than a doping concentration of said cathode diffusion layer, and a doping concentration of said avalanche layer is greater than a doping concentration of said substrate.
9. A photosensitive pixel module according to claim 2, further comprising:
the light-sensitive pixel unit comprises a light-sensitive pixel unit, a signal acquisition layer, a signal acquisition circuit and a light-sensitive pixel unit, wherein the light-sensitive pixel unit is arranged on the light-sensitive pixel unit, the signal acquisition layer is stacked on one side of the light-sensitive pixel unit far away from the light inlet side, the signal acquisition layer comprises.
10. A photosensitive pixel module according to claim 1, wherein the photosensitive pixel cell comprises:
a substrate;
the cathode layer is arranged on the substrate, a second accommodating part is arranged on the cathode layer, and a second opening is formed in one side, far away from the substrate, of the second accommodating part;
an avalanche layer embedded in a side of the cathode layer away from the substrate and exposed to the second opening;
and the anode layer is arranged on one side of the avalanche layer far away from the substrate.
11. A photosensitive pixel module as defined in claim 10, wherein the cathode layer includes a first type of dopant, the avalanche layer and the anode layer include a second type of dopant, and a doping concentration of the avalanche layer is less than a doping concentration of the anode layer.
12. A photosensitive pixel module according to claim 10, further comprising:
the pixel acquisition layer is stacked on the light inlet side of the photosensitive pixel unit and comprises a signal acquisition circuit, and the signal acquisition circuit is connected with the photosensitive pixel unit.
13. A photosensitive pixel module according to any one of claims 2-12, wherein the guard ring comprises:
and the deep groove isolation is in a closed ring shape and surrounds the plurality of photosensitive pixel units.
14. A photosensitive pixel module according to any of claims 2-12, wherein the guard ring comprises:
a semiconductor guard ring in the shape of a closed ring, the semiconductor guard ring surrounding a plurality of the light-sensitive pixel cells.
15. A photosensitive pixel module according to any one of claims 1-12, wherein the shallow trench isolation is filled with an oxide.
16. A photosensitive pixel module according to any one of claims 1-12, further comprising:
the light convergence layer is arranged on the light inlet side of the photosensitive pixel unit and used for converging light rays in the photosensitive pixel unit.
17. A photosensitive pixel module according to any of claims 1-12, wherein the thickness of the photosensitive pixel module is from 3 microns to 10 microns.
18. An image sensor comprising a photosensitive pixel module according to any one of claims 1-17.
19. An electronic device, characterized in that the electronic device comprises an image sensor according to claim 18.
CN202010548644.XA 2020-06-16 2020-06-16 Photosensitive pixel module, image sensor and electronic device Pending CN111769126A (en)

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