WO2022217760A1 - 新型光电二极管结构、制备方法及电路结构 - Google Patents

新型光电二极管结构、制备方法及电路结构 Download PDF

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WO2022217760A1
WO2022217760A1 PCT/CN2021/104240 CN2021104240W WO2022217760A1 WO 2022217760 A1 WO2022217760 A1 WO 2022217760A1 CN 2021104240 W CN2021104240 W CN 2021104240W WO 2022217760 A1 WO2022217760 A1 WO 2022217760A1
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doping
region
functional
doping region
concentration
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PCT/CN2021/104240
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French (fr)
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黄尊恺
李全泽
汪辉
祝永新
汪宁
田犁
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中国科学院上海高等研究院
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Priority to US18/011,515 priority Critical patent/US20240030368A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035272—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
    • H01L31/03529—Shape of the potential jump barrier or surface barrier
    • 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
    • H01L27/1443—Devices controlled by radiation with at least one potential jump or surface barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/02016—Circuit arrangements of general character for the devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/103—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN homojunction type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/02016—Circuit arrangements of general character for the devices
    • H01L31/02019—Circuit arrangements of general character for the devices for devices characterised by at least one potential jump barrier or surface barrier

Definitions

  • the invention belongs to the field of photoelectric conversion devices, and in particular relates to a novel photodiode structure, a preparation method and a circuit structure.
  • Photodiodes are semiconductor devices that respond to energetic particles and photons, which absorb photons or energetic particles and generate a current in an external circuit proportional to the incident power. Photodiodes are used in a wide variety of applications and research areas such as spectroscopy, photography, analytical instruments, optical position sensors, beam alignment, surface characterization, laser rangefinders, optical communications, and medical imaging instruments.
  • charge transfer is based on a complex process driven by various coupled processes, including drift, diffusion, and self-inductive drift.
  • diffusion is the dominant factor
  • the charge transfer time is proportional to the square of the distance
  • PIN-PD external biasing technology
  • Diode shaping is that it is complex to implement and may reduce the fill factor; it is true that charge transfer speed increases can be achieved using multiple doping techniques, but they are usually implemented using several additional masks, each corresponding to A doping level, which greatly increases the manufacturing cost.
  • science, medical imaging and other fields have great demands and requirements for large-scale photodiodes, especially in improving the efficiency of charge transfer. Sex and other aspects need to be further optimized.
  • the purpose of the present invention is to provide a novel photodiode structure, preparation method and circuit structure, which are used to solve the problem that the internal charge transfer time, efficiency and photo-generated charge collection are difficult to be effectively improved in the prior art. And other issues.
  • the present invention provides a novel photodiode structure, the photodiode structure includes:
  • a substrate of a first doping type the substrate having a first doping concentration
  • a functional doping region of the second doping type is formed in the substrate, and the doping concentration distribution of the functional doping region is non-uniform doping, so as to form a potential gradient in the functional doping region;
  • An auxiliary doping region of the second doping type is formed in the functional doping region, connecting the gate structure and the functional doping region, and the auxiliary doping region and the surface doping region There is a distance therebetween, and the doping concentration of the auxiliary doping region is greater than the doping concentration of the functional doping region.
  • the shapes of the surface doping region and the auxiliary doping region both include a ring shape
  • the gate structure is located in the ring structure formed by the auxiliary doping region, and the gate structure is arranged in a ring shape
  • An inner doping region is also formed in the corresponding functional doping region in the annular gate structure, and the inner doping region and the auxiliary doping region have the same doping type and doping concentration.
  • the first doping type is p-type
  • the second doping type is n-type
  • the surface doping region, the functional doping region and the substrate form a PNP-type structure.
  • the doping concentration distribution of the functional doping region includes any one of linear distribution and square root distribution.
  • the present invention also provides a method for preparing a novel photodiode structure, wherein the novel photodiode structure of the present invention is preferably prepared by the method of the present invention, and of course other methods are also possible, and the preparation method includes the following steps:
  • a substrate of a first doping type having opposing first and second sides, the substrate having a first doping concentration
  • a functional doping region of a second doping type is formed in the substrate from the first face, wherein the doping concentration distribution of the functional doping region is non-uniform doping, so that the functional doping region is A potential gradient is formed in the region;
  • a surface doped region of a first doping type is formed in the functional doped region from the first face, and the surface doped region has a second doping concentration;
  • An auxiliary doping region of a second doping type is formed in the functional doping region from the first surface, the auxiliary doping region connects the gate structure and the functional doping region, and the auxiliary doping region There is a distance between the impurity region and the surface doping region, and the doping concentration of the auxiliary doping region is greater than the doping concentration of the functional doping region.
  • the functional doped region with a predetermined concentration distribution is formed based on ion implantation and implanted ion diffusion.
  • the step of forming the functional doping region based on the ion implantation includes: the concentration distribution of the functional doping region after the ion implantation is: Among them, RA is the average range of impurities in the substrate and corresponds to the implantation energy, and corresponds to the doping concentration peak in the implantation direction, ⁇ RA is the depth changed by half of the doping concentration peak, and C y represents the implantation concentration in the direction; y represents the position in the implantation direction, and C 0 represents the implanted ion concentration.
  • the step of forming the functional doped region based on the implanted ion diffusion includes: Among them, x0 represents the ion implantation point, x represents the distance from the ion implantation point, is the characteristic length of the diffusion process, D is the diffusion coefficient, w is the distance that widens the x 0 point to both sides, and C(x, t) is the concentration at the x position at the diffusion time t.
  • a mask is fabricated on the substrate, ion implantation is performed based on the mask to form the functional doped region, and a plurality of nested annular openings are formed in the mask, wherein, The size of the annular opening is set according to the concentration of the corresponding position of the opening, and the setting method includes: where C 0 represents the implanted ion concentration, xi represents the center position of the ith mask opening, l represents the characteristic length of the diffusion process under each mask opening, wi represents the width of the ith mask opening C(x) represents the concentration distribution function in the x direction.
  • the present invention also provides a circuit structure including the novel photodiode structure according to any one of the above solutions, and the circuit structure includes:
  • the surface doped region is grounded
  • a charge receiving module electrically connected to the drain structure of the novel photodiode structure, and receiving the charges stored in the novel photodiode structure during reset, the charge receiving module comprising an integrating capacitor and a control switch;
  • An amplifying module the two input ends are respectively electrically connected with the comparison voltage and the drain structure, the output end outputs the amplified signal, and the amplifying module includes a charge amplifier and a control switch.
  • the output end of the amplifying module is connected to the pixel column output, and the noise on the pixel output is: where K is Boltzmann's constant, T is temperature, and C diode (VREF) is the capacitance of the voltage at VREF.
  • the novel photodiode structure, preparation method and circuit structure of the present invention can drive the optical residual carrier by forming a non-uniformly doped functional doped region, thereby forming a self-built potential difference in the functional doped region.
  • the direction of movement for example, can make the photogenerated carriers move faster under the action of the potential difference, so that the collected carriers will directly enter the subsequent circuits through the transport gate (TG).
  • the auxiliary doping region of the ring structure can increase the area for receiving charges, can receive the transported carriers more quickly, and can further improve the transport efficiency of photogenerated carriers.
  • FIG. 1 is a flow chart showing the fabrication of a novel photodiode structure in an example of the present invention.
  • FIG. 2 is a schematic diagram showing the structure of the substrate provided in the preparation of the novel photodiode structure in an example of the present invention.
  • FIG. 3 is a schematic diagram showing the structure of forming a functional doped region in the preparation of a novel photodiode structure in an example of the present invention.
  • FIG. 4 is a schematic structural diagram of forming a surface doped region, an auxiliary doped region, a gate structure and a source structure in the preparation of a novel photodiode structure in an example of the present invention.
  • Figure 5 shows a top view of a novel photodiode structure fabricated in another example of the present invention.
  • FIG. 6 shows a schematic cross-sectional view of the novel photodiode structure in the example of FIG. 5 .
  • FIG. 7 is a schematic diagram showing the internal structure of the transfer tube of the novel photodiode structure prepared in an example of the present invention.
  • FIG. 8 is a schematic diagram illustrating the formation of a functional doped region mask in the fabrication of a novel photodiode structure in an example of the present invention.
  • FIG. 9 is a schematic diagram showing the structure of a dual-gain pixel circuit in an example of the present invention.
  • spatially relative terms such as “below,” “below,” “below,” “below,” “above,” “on,” etc. may be used herein to describe an element shown in the figures or The relationship of a feature to other components or features. It will be understood that these spatially relative terms are intended to encompass other directions of the device in use or operation than those depicted in the figures.
  • a layer when referred to as being 'between' two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Additionally, "between” as used in the present invention includes both endpoints.
  • references where a first feature is "on" a second feature can include embodiments in which the first and second features are formed in direct contact, and can also include further features formed over the first and second features. Embodiments between the second features such that the first and second features may not be in direct contact.
  • the present invention provides a novel photodiode structure, wherein the photodiode structure includes: a substrate 101 , a functional doping region 102 , a surface doping region 103 , an auxiliary doping region 105 and a gate structure 104.
  • a source structure 106 may also be included to form a conventional connection of the pixels, which may be designed according to actual requirements.
  • the novel photodiode structure of the present invention includes a substrate 101 and involves optimization of photoelectric conversion and carrier transport performance.
  • the charge transfer distance also increases, and the charge transfer time increases accordingly.
  • the speed of internal charge transfer directly affects the working efficiency of the pixel and upper-layer circuits.
  • the invention intends to design a photodiode device structure which improves the internal charge transfer speed and the photo-generated charge collection efficiency under the premise of relatively low production cost and technological difficulty.
  • the substrate 101 has doping of the first doping type.
  • the first doping type may be n-type or p-type, and correspondingly, the second doping type is p-type or n-type.
  • the first doping type is p-type and the second doping type is n-type.
  • the substrate 101 is a silicon substrate, and in a specific example, a P-type silicon wafer doped with low concentration boron is used as the substrate (p-).
  • the substrate 101 of the first doping type has an opposite first surface and a second surface.
  • the upward surface as shown in the figure is used as the first surface, which is used for Other device functional layers are formed in the substrate 101 .
  • the shape of the substrate 101 in the top view may be a rectangle, and may also be a hexagon, an octagon, a circle, etc., but is not limited to this, and can be selected according to actual needs.
  • the photodiode structure of the present invention further includes a functional doping region 102 , and the functional doping region 102 has a second type doping, which is n-type doping in this embodiment, such as n-doping .
  • the functional doping region 102 is non-uniformly doped. Based on the above design, after photogenerated carriers are collected into the functional doping region 102 (eg n-), due to the non-uniform doping, this region will A potential gradient related to the concentration distribution is formed, and the transport of carriers in this region can be controlled based on the potential gradient.
  • a self-built driving potential can be formed in this region, so that the carriers move in the n+ direction, which is understandable Yes, as long as the potential difference formed in the functional doped region can produce the effect of driving the photo-generated carriers to move toward the auxiliary doped region.
  • the method of the present invention can greatly improve the transport speed of carriers.
  • the manufacturing difficulty of the method is greatly reduced, and the limitation of some practical use scenarios is eliminated.
  • the doping concentration distribution of the functional doping region 102 includes any one of linear distribution and square root distribution.
  • the doping concentration increases linearly in the direction of the arrow in the figure, that is, toward the direction of n+.
  • the doping concentration may be increased by the square root in the direction of the arrow.
  • Linear and square root distributions are only typical doping distributions that form potential gradients. Our method can theoretically achieve doping with arbitrary distribution functions.
  • the shape of the functional doped region 102 in a plan view may be a rectangle, or a shape such as a hexagon, an octagon, a circle, etc., but is not limited to this, and can be selected according to actual needs.
  • the functional doped region 102 is located in the substrate 101 , and is formed by ion implantation from the first surface of the substrate 101 .
  • a low-concentration doped N-type region (n-) is fabricated using a non-uniform doping method, and the doping of the n-region can use linear distributions, square root distributions, and other more complex functional distributions.
  • the photodiode structure of the present invention further includes a surface doping region 103 , and the surface doping region 103 of the first doping type is formed in the functional doping region 102 and located in the first doping region 102 .
  • One side is one side, and the surface doping region 103 has a second doping concentration.
  • the second doping concentration is greater than the first doping concentration.
  • the edge of one end of the surface doped region 103 away from the gate structure is aligned with the outer edge of the functional doped region 102 .
  • a thin layer of heavily doped P-type region (p+) is deposited over the low-concentration doped N-type region.
  • the shape of the surface doped region 103 in a plan view may be a rectangle, or a hexagon, an octagon, a circle, or the like, but is not limited thereto, and can be selected according to actual needs.
  • the photodiode structure of the present invention further includes a gate structure 104 located on the first surface of the substrate 101 .
  • the preparation process and material of the gate structure 104 can adopt the existing design.
  • the gate structure 104 is connected to the functional doped region 102 , that is, the edge of the gate structure 104 close to the functional doped region 102 and the functional doped region 102
  • the edges on the side close to the gate structure are aligned and located on the same plane, and the two do not overlap.
  • other positional relationships that can exert the effects of the present invention are also possible.
  • the photodiode structure of the present invention further includes an auxiliary doping region 105 of the second doping type, connecting the gate structure 104 and the functional doping region 102 , and the auxiliary doping region 105 It is formed at least in the functional doping region 102, on the side of the first surface, and there is a distance between the auxiliary doping region 105 and the surface doping region 103, and the auxiliary doping region 105 is The doping concentration is greater than the doping concentration of the functional doping region 102 . In an example, the doping concentration of the auxiliary doping region 105 is greater than the concentration at any position of the functional doping region 102 , which is not an order of magnitude.
  • the substrate eg, p-substrate
  • the functional doped region eg, n-doped region
  • the surface doped region eg, p+ doped region
  • the auxiliary doped region eg, Such as n+ doping area
  • the concentration of these areas will be different in different process factories, but in fact, it should be negotiated with the factory according to the needs, for example, in an example, p- is 10 15 ⁇ 10 16 cm -3 ; n - at 10 15 ⁇ 10 16 cm -3 ; n+ at 10 18 ⁇ 10 20 cm -3 ; but this is just an example, as long as the doping concentration satisfies n- less than n, n is the intrinsic carrier in the silicon wafer concentration, and so on.
  • the shape of the auxiliary doping region 105 in a plan view may be a rectangle, or a shape such as a hexagon, an octagon, a circle, etc., but is not limited thereto, and can be selected according to actual needs.
  • the edge of the auxiliary doped region 105 on the side close to the gate structure is aligned with the edge of the functional doped region 102 on the side close to the gate structure. Together, the gate structure is realized. 104 and the auxiliary doping region 105 are connected.
  • the surface doping region 103 , the functional doping region 102 and the substrate 101 form a PNP type structure, so that most regions of the photodiode are completely depleted in the circuit reset stage, which improves the photo-generation carrier collection efficiency.
  • the auxiliary doping region 105 after photo-generated carriers are collected into, for example, the n-region (the functional doping region 102), due to the non-uniform doping, this region will form a concentration distribution related Potential gradients, compared to uniform doping, can greatly increase the speed of carrier transport.
  • the auxiliary doping region 105 may also be a drain structure of a device, and together with the gate structure 104 and the source structure 106 constitute a MOS device.
  • the n- region will form a built-in potential difference pointing in the direction of the n+ region, and the photogenerated carriers in the n- region will be accelerated to move to the n+ region under the action of the potential difference area.
  • the surface doping region 103 can also have a blocking effect. Due to the blocking of the surface p+ region (surface doping region 103 ), the tendency of the diffusion movement is also limited in the horizontal direction, which accelerates the photo-generated carriers The speed of the moving n+ area.
  • the upper surfaces of the substrate 101 , the functional doping region 102 , the surface doping region 103 and the auxiliary doping region 105 are flush, and the depth of the functional doping region 102 smaller than the depth of the substrate 101, the depth of the surface doping region 103 is smaller than the depth of the functional doping region 102, the depth of the auxiliary doping region 105 is smaller than the depth of the functional region 102, in a further example , the depth of the surface doping region 103 is equal to the depth of the auxiliary doping region 105 .
  • an appropriate depth range can also be selected according to actual needs.
  • the shapes of the surface doping region 203 and the auxiliary doping region 205 include a ring shape, and the gate structure 204 is located in the ring structure formed by the auxiliary doping region 205 , and the gate structure 204 is also arranged in a ring shape, and an inner doping region is formed in the corresponding functional doping region 202 in the ring gate structure 204 to form a source structure 206 , and the inner doping region 206 is formed.
  • the doping type and doping concentration of the impurity region and the auxiliary doping region 205 are the same.
  • the auxiliary doping region 105 is disposed on the periphery of the gate structure 104 in a ring shape.
  • the ring structure increases the area, such as the n+ region of the ring structure, which increases the area for receiving charges, can receive the carriers transported by n- more quickly, and can further improve the transport efficiency of photogenerated carriers.
  • a heavily doped N-type region (n+) is fabricated through ion implantation in a small annular region connected to the transfer gate (TG) to obtain the auxiliary doped region 105 .
  • the gate structure 104 , the surface doping region 103 and the auxiliary doping region 105 form concentric rings.
  • the first doping type is p-type
  • the second doping type is n-type
  • the surface doping region, the functional doping region and the substrate form a PNP-type structure.
  • the first and second doping types can also be interchanged.
  • FIG. 7 shows a schematic diagram of the transport process of photogenerated carriers, when the diode reaches its reset voltage, most of the voltage drop is in the N-type heavily doped region (n+ ), the N-type low-doped region (n-) is completely depleted, and when an optical signal is input, photogenerated carriers will be quickly collected into the n- region.
  • the n- region Due to the non-uniform doping, the n- region will form a built-in potential difference pointing to the direction of the n+ region, and the photo-generated carriers in the n- region will be accelerated to move to the n- region under the action of the potential difference.
  • the tendency of diffusion movement is also limited in the horizontal direction, which accelerates the speed of the n+ region where photogenerated carriers move. The carriers collected in the n+ region will directly enter the subsequent circuits through the transport gate (TG).
  • the present invention also provides a method for preparing a novel photodiode structure, wherein the novel photodiode structure described above in the embodiment of the present invention is preferably prepared by the method in this embodiment of the present invention.
  • the method is prepared, and the descriptions in the specific photodiode structure and preparation method can be referred to each other, and redundant details are not repeated.
  • FIG. 1 only shows the novel photodiode structure in an example. preparation steps.
  • a substrate 101 of a first doping type is provided, having opposite first and second surfaces, and the substrate 101 has a first doping concentration.
  • the features of the substrate 101 can be referred to the description in the device structure.
  • the substrate 101 may be a fully doped substrate structure, or may be a doped region obtained by partially doping an initial substrate (eg, a silicon substrate), which is used to prepare subsequent device structures Floor.
  • a functional doped region 102 of the second doping type is formed in the substrate 101 from the first surface, wherein the functional doped region 102 is The doping concentration profile is non-uniform doping.
  • the functional doped region 102 may be formed by ion implantation based on a mask.
  • the functional doped region 102 with a predetermined concentration distribution is formed based on ion implantation and implanted ion diffusion.
  • the formation is based on two stages of ion implantation and implanted ion diffusion, that is, a realization theory of non-uniform doping distribution is proposed, which can guide the design of non-uniform doping structures with any concentration distribution function.
  • the whole doping process is divided into two stages: ion implantation and diffusion, which are described as follows:
  • the ion implantation energy D and the ion implantation concentration C 0 are set.
  • the time to complete the ion implantation process is very short, and the main parameters of concern are the implantation energy and the implantation concentration.
  • the average range RA of a certain impurity in silicon can be obtained by setting the implantation energy in the process.
  • the value of this longitudinal depth corresponds to the maximum concentration after implantation, which is approximately equal to the concentration during implantation, and at the point where the average range is located,
  • the distribution of impurity concentration in the vertical direction can be approximated as a Gaussian function, and the depth of the change of the peak value by half is recorded as ⁇ RA , and the vertical concentration distribution function can be obtained as:
  • C y represents the concentration in the implantation direction
  • y represents the position in the implantation direction.
  • the ion doping concentration at any vertical position after implantation can be obtained from the ion implantation energy D and the ion implantation concentration C 0 .
  • C(x,t) represents the doping concentration at the x position at the time of diffusion t.
  • it is the diffusion length in a single direction, let is the characteristic length of the diffusion process, representing the diffusion distance in one-dimensional direction;
  • the ion implantation is generally a mask gap instead of a point, and the point x 0 is widened to both sides by w, and w represents the mask opening
  • the width of , representing the actual width of the corresponding mask gap is 2w, then the above formula can be expressed as:
  • each actual physical quantity has a correspondence in the formula, and the doping concentration corresponding to any position at any time can be obtained.
  • the analysis of the first-stage ion implantation is the distribution of an approximate vertical line, and the lateral diffusion of the process of forming a normal distribution is not considered. In fact, due to the short time, this approximation is effective.
  • Each point corresponds to a concentration, This concentration is C 0 in the second-stage formula, which is the initial concentration of the diffusion process; the second-stage formula calculates the final concentration distribution.
  • one ion implantation can be performed with n mask openings with different spacings, and the characteristic length corresponding to each mask opening is defined by the physical quantity of the formula where x1 is the center position of the first mask opening, xn is the center position of the last mask opening, and the width of the ith mask opening
  • the mask opening determines the formula, and the integral is approximated as a summation, then there are:
  • the formula can be understood that the infinite mask openings are exactly the same as the given doping distribution function.
  • This calculation method is very universal, and the number of mask openings can be determined according to actual needs. The more accurate, the general 100-micron device with ten openings for linear non-uniform doping is already very accurate.
  • a mask 301 is fabricated on the substrate 101 , and ion implantation is performed based on the mask to form the functional doped regions 102 , and several functional doped regions 102 are formed in the mask.
  • the nested annular mask opening 301a wherein the size of the annular opening is set according to the concentration of the corresponding position of the opening.
  • the present invention proposes a method for realizing a novel annular structure non-uniformly doped region (n-), the schematic diagram of which is shown in FIG. 8 .
  • Different application environments can adopt a variety of different doping methods.
  • the present invention adopts the method of depositing oxide to manufacture the mask, divides the area to be doped into multiple sections, and each section has an independent mask.
  • One ion implantation, combined with a long time of diffusion, can achieve arbitrary distribution of non-uniform doping.
  • the actual diffusion time can be determined based on the calculated characteristic length L, which can be slightly extended on this basis, and can be set according to actual needs .
  • a surface doping region 103 of the first doping type is formed in the functional doping region 102 from the first surface, and the surface doping region has The second doping concentration can be doped by using the existing method.
  • a gate structure 104 is formed on the first surface of the substrate 101 .
  • an auxiliary doping region 105 of the second doping type is formed in the functional doping region 102 from the first surface, and the auxiliary doping region 105 is connected to the There is a distance between the gate structure 104 and the functional doping region 102, and there is a distance between the auxiliary doping region 105 and the surface doping region 103, and the doping concentration of the auxiliary doping region 105 is greater than that of the functional doping region 105. Doping concentration of the doped region 102 .
  • the present invention also provides a circuit structure using the novel photodiode structure according to any one of the above solutions, and the circuit structure includes:
  • the surface doped region 103 is grounded
  • a charge receiving module 400 electrically connected to a drain structure, wherein an auxiliary doped region can be used as the drain structure, receives the charge stored in the novel photodiode structure during reset, including an integrating capacitor and a control switch;
  • the amplifying module 500 two input ends are respectively electrically connected to the comparison voltage and the drain structure, and outputs the amplified signal, including a charge amplifier and a control switch.
  • the output end of the charge amplifier is connected to one end of the integrating capacitor, and is further connected to the column output of the pixel.
  • FIG. 9 shows a schematic circuit diagram of the novel photodiode structure of the present invention applied to a double-gain pixel.
  • the diode reaches its reset voltage, most of the voltage drops in the N-type heavily doped region (n+), that is, the auxiliary doped regions 105, while the low doped regions are completely depleted. Electrons are collected in the N-type low-doped region (n-), ie, the functionally-doped region 102, and rapidly transferred to the N-type heavily doped region (n+) under the action of a gradient potential.
  • the TG gate structure
  • the charge stored on the photodiode will move to the integrating capacitors C1/C2.
  • the noise measured on the pixel output is associated with the reset operation:
  • the C diode (VREF) is the capacitance of the voltage at VREF
  • K is the Boltzmann constant
  • K 1.38 ⁇ 10 ⁇ 23 m 2 kgs ⁇ 2 K ⁇ 1
  • T represents the temperature. Due to the use of the diode structure of the present invention, this value is relatively small, which means that the floor of pixel noise is also small, which can further improve the imaging effect.
  • the invention proposes a theory, structure and implementation method of a photodiode device. Compared with the prior art, on the basis of reducing the difficulty and cost of industrial manufacturing, the transfer speed and collection efficiency of charges in large-size photodiodes are improved. , which can reduce the noise generated by dark current.
  • the novel photodiode structure, preparation method and circuit structure of the present invention can drive optical residual carriers by forming a non-uniformly doped functional doped region, thereby forming a self-built potential difference in the functional doped region.
  • the photogenerated carriers can be accelerated to move under the action of the potential difference, so that the collected carriers will directly enter the subsequent circuits through the transport gate (TG).
  • the auxiliary doping region of the ring structure can increase the area for receiving charges, can receive the transported carriers faster, and can further improve the transport efficiency of photogenerated carriers. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

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Abstract

本发明提供一种新型光电二极管结构、制备方法及电路结构，新型光电二极管结构包括：第一掺杂类型衬底、第二掺杂类型功能掺杂区、第一掺杂类型表面掺杂区及第二掺杂类型辅助掺杂区。本发明通过形成非均匀掺杂的功能掺杂区，在功能掺杂区中形成自建电势差，可以驱动光剩载流子的运动方向，如可以使光生载流子在电势差的作用下加速移动，使得被收集的载流子会直接通过运输门(TG)进入后续的电路。另外，环状结构的辅助掺杂区可以增大接收电荷的面积，能更快地接收运输来的载流子，能进一步提升光生载流子的运输效率。

Description

新型光电二极管结构、制备方法及电路结构 技术领域
本发明属于光电转换器件领域，特别是涉及一种新型光电二极管结构、制备方法及电路结构。
背景技术
光电二极管是响应高能粒子和光子的半导体器件，其吸收光子或高能粒子，并在外部电路中产生与入射功率成比例的电流。光电二极管应用广泛，涉及光谱学、摄影、分析仪器、光学位置传感器、光束对准、表面表征、激光测距仪、光学通信和医学成像仪器等众多应用和研究领域。
目前，光电二极管普遍的研究趋势是设计更小尺寸的器件，对大尺寸器件性能提升的研究较少。然而，在科学和医学成像等应用中，由于信号强度的限制，小尺寸二极管不再具备优势，往往需要大尺寸光电二极管来改善信噪比性能。在大尺寸光电二极管器件研究领域，一个核心设计挑战是如何实现快速、完整的电荷转移，这对于高速低噪声成像应用中至关重要。通常，像素的工作效率由读出电子器件的速度及其内部电荷转移的速度决定，然而，随着光电二极管尺寸的增大，电荷传输距离也随之增加，电荷转移时间及效率将不可避免地受到影响，必须对其进行优化。
其中，电荷转移是基于各种耦合过程驱动的复杂过程，包括漂移、扩散和自感漂移。在没有电场的情况下，扩散是主要因素，电荷转移时间与距离的平方成正比，在有电场的情况下，电荷转移时间与距离成正比。目前已经提出了多种方法来提高大尺寸光电二极管中的电荷转移速度，包括Diode shaping技术、多次掺杂技术、外部偏置技术、PIN-PD等。Diode shaping的缺点是实现起来很复杂，并且可能会降低填充因子；使用多次掺杂技术的确可以实现电荷转移速度的提高，但是它们通常使用几个附加的掩模来实现，每个掩模对应一个掺杂水平，这大大增加了制造成本。总的来说，科学、医学成像等领域对大尺寸光电二极管有着极大的需求和要求，特别是在提升电荷转移的效率上，目前的主流的方法在工艺复杂程度、实际制造成本、普适性等方面都需要进一步地优化。
因此，如何提供一种新型光电二极管结构、制备方法及电路结构，以解决现有技术中的上述问题实属必要。
发明内容
鉴于以上所述现有技术的缺点，本发明的目的在于提供一种新型光电二极管结构、制备方法及电路结构，用于解决现有技术中内部电荷转移时间、效率以及光生电荷收集难以得到有效改善等问题。
为实现上述目的及其他相关目的，本发明提供一种新型光电二极管结构，所述光电二极管结构包括：
第一掺杂类型的衬底，所述衬底具有第一掺杂浓度；
第二掺杂类型的功能掺杂区，形成在所述衬底中，所述功能掺杂区的掺杂浓度分布为非均匀掺杂，以在所述功能掺杂区形成电势梯度；
第一掺杂类型的表面掺杂区，自所述功能掺杂区的上表面形成在所述功能掺杂区中，且所述表面掺杂区具有第二掺杂浓度；
栅极结构，位于所述衬底上；以及
第二掺杂类型的辅助掺杂区，形成在所述功能掺杂区中，并连接所述栅极结构与所述功能掺杂区，且所述辅助掺杂区与所述表面掺杂区之间具有间距，所述辅助掺杂区的掺杂浓度大于所述功能掺杂区的掺杂浓度。
可选地，所述表面掺杂区及所述辅助掺杂区的形状均包括环形，所述栅极结构位于所述辅助掺杂区构成环形结构内，且所述栅极结构呈环形设置，环形的所述栅极结构内对应的所述功能掺杂区中还形成有内部掺杂区，所述内部掺杂区与所述辅助掺杂区的掺杂类型及掺杂浓度均相同。
可选地，所述第一掺杂类型为p型，所述第二掺杂类型为n型，所述表面掺杂区、所述功能掺杂区及所述衬底形成PNP型结构。
可选地，所述功能掺杂区的掺杂浓度分布方式包括线性分布、平方根分布中的任意一种。
另外，本发明还提供一种新型光电二极管结构的制备方法，其中，本发明的新型光电二极管结构优选采用本发明的方法制备，当然也可以是其他方法，所述制备方法包括如下步骤：
提供第一掺杂类型的衬底，具有相对的第一面和第二面，所述衬底具有第一掺杂浓度；
自所述第一面在所述衬底中形成第二掺杂类型的功能掺杂区，其中，所述功能掺杂区的掺杂浓度分布为非均匀掺杂，以在所述功能掺杂区形成电势梯度；
自所述第一面在所述功能掺杂区中形成第一掺杂类型的表面掺杂区，且所述表面掺杂区具有第二掺杂浓度；
在所述衬底的第一面上形成栅极结构；以及
自所述第一面在所述功能掺杂区形成第二掺杂类型的辅助掺杂区，所述辅助掺杂区连接 所述栅极结构与所述功能掺杂区，且所述辅助掺杂区与所述表面掺杂区之间具有间距，所述辅助掺杂区的掺杂浓度大于所述功能掺杂区的掺杂浓度。
可选地，基于离子注入及注入离子扩散形成预设浓度分布的所述功能掺杂区。
可选地，基于所述离子注入形成所述功能掺杂区的步骤包括：离子注入后所述功能掺杂区的浓度分布为：
Figure PCTCN2021104240-appb-000001
其中，R A为杂质在衬底中的平均射程且与所述注入能量对应，并在注入方向上对应掺杂浓度峰值，ΔR A为掺杂浓度峰值下降一半所改变的深度，C y代表注入方向上的浓度；y代表注入方向上的位置，C 0代表注入离子浓度。
可选地，基于所述注入离子扩散形成所述功能掺杂区的步骤包括：
Figure PCTCN2021104240-appb-000002
其中，x0代表离子注入点，x代表与离子注入点之间的距离，
Figure PCTCN2021104240-appb-000003
为扩散过程的特征长度，D为扩散系数，w为将x 0点向两边分别拓宽的距离，C(x,t)为扩散时间t时x位置的浓度。
可选地，在所述衬底上制作掩膜板，基于所述掩膜板进行离子注入形成所述功能掺杂区，所述掩膜板中形成有若干个套置的环形开口，其中，所述环形开口的尺寸依据开口对应位置的浓度设置，设置方式包括：
Figure PCTCN2021104240-appb-000004
其中，C 0代表注入离子浓度，xi代表第i个掩膜开口的中心位置，l代表每个掩膜开口下扩散过程的特征长度，
Figure PCTCN2021104240-appb-000005
wi代表第i个掩膜开口的宽度
Figure PCTCN2021104240-appb-000006
C(x)代表x方向上的浓度分布函数。
另外，本发明还提供一种包括如上述方案中任意一项所述的新型光电二极管结构的电路结构，所述电路结构包括：
所述新型光电二极管结构，所述表面掺杂区接地；
电荷接收模块，与新型光电二极管结构的漏极结构电连接，在复位期间接收存储在所述所述新型光电二极管结构中的电荷，所述电荷接收模块包括积分电容器及控制开关；
放大模块，两输入端分别与比较电压及所述漏极结构电连接，输出端将放大的信号输出，所述放大模块包括电荷放大器及控制开关。
可选地，所述放大模块的输出端与像素列输出相连，在像素输出上的噪声为：
Figure PCTCN2021104240-appb-000007
其中，K是玻尔兹曼常数，T代表温度，C 二极管(VREF)是电压在VREF处的电容。
如上所述，本发明的新型光电二极管结构、制备方法及电路结构，通过形成非均匀掺杂的功能掺杂区，从而在功能掺杂区中形成自建电势差，可以驱动光剩载流子的运动方向，如可以使光生载流子会在电势差的作用下加速移动，使得被收集的载流子会直接通过运输门(TG)进入后续的电路。另外，环状结构的辅助掺杂区可以增大接收电荷的面积，能更快地接收运输来的载流子，能进一步提升光生载流子的运输效率。
附图说明
图1显示为本发明一示例中制备新型光电二极管结构的流程图。
图2显示为本发明一示例中制备新型光电二极管结构中提供衬底的结构示意图。
图3显示为本发明一示例中制备新型光电二极管结构中形成功能掺杂区的结构示意图。
图4显示为本发明一示例中制备新型光电二极管结构中形成表面掺杂区、辅助掺杂区、栅极结构及源极结构的结构示意图。
图5显示为本发明另一示例中制备的新型光电二极管结构的俯视图。
图6显示为图5示例中新型光电二极管结构的截面示意图。
图7显示为本发明一示例中制备的新型光电二极管结构的传输管内部结构工作示意图。
图8显示为本发明一示例中制备新型光电二极管结构中形成功能掺杂区掩膜示意图。
图9显示为本发明一示例中双增益像素电路结构示意图。
元件标号说明
101、201               衬底
102、202               功能掺杂区
103、203               表面掺杂区
104、204               栅极结构
105、205               辅助掺杂区
106、206               源极结构
301                    掩膜板
301a                   掩膜开口
400                    电荷接收模块
500                    放大模块
S1～S5                 步骤
具体实施方式
以下通过特定的具体实例说明本发明的实施方式，本领域技术人员可由本说明书所揭露的内容轻易地了解本发明的其他优点与功效。本发明还可以通过另外不同的具体实施方式加以实施或应用，本说明书中的各项细节也可以基于不同观点与应用，在没有背离本发明的精神下进行各种修饰或改变。
如在详述本发明实施例时，为便于说明，表示器件结构的剖面图会不依一般比例作局部放大，而且所述示意图只是示例，其在此不应限制本发明保护的范围。此外，在实际制作中应包含长度、宽度及深度的三维空间尺寸。
为了方便描述，此处可能使用诸如“之下”、“下方”、“低于”、“下面”、“上方”、“上”等的空间关系词语来描述附图中所示的一个元件或特征与其他元件或特征的关系。将理解到，这些空间关系词语意图包含使用中或操作中的器件的、除了附图中描绘的方向之外的其他方向。此外，当一层被称为在两层“之间”时，它可以是所述两层之间仅有的层，或者也可以存在一个或多个介于其间的层。另外，本发明中使用的“介于……之间”包括两个端点值。
在本申请的上下文中，所描述的第一特征在第二特征“之上”的结构可以包括第一和第二特征形成为直接接触的实施例，也可以包括另外的特征形成在第一和第二特征之间的实施例，这样第一和第二特征可能不是直接接触。
需要说明的是，本实施例中所提供的图示仅以示意方式说明本发明的基本构想，遂图示中仅显示与本发明中有关的组件而非按照实际实施时的组件数目、形状及尺寸绘制，其实际实施时各组件的型态、数量及比例可为一种随意的改变，其组件布局型态也可能更为复杂。
如图4所示，本发明提供一种新型光电二极管结构，其中，所述光电二极管结构包括：衬底101、功能掺杂区102、表面掺杂区103、辅助掺杂区105以及栅极结构104。另外，还可以包括源极结构106，以形成像素的常规连接，可依据实际需求设计。
下面将结合附图详细说明本发明的结构。
如图4所述，本发明的新型光电二极管结构包括衬底101，涉及光电转换及载流子运输性能的优化。对于大尺寸的光电二极管，随着器件尺寸的增大，电荷传输距离也随之增加，电荷转移时间也会相应增加，而内部电荷转移的速度直接影响着像素以及更上层电路的工作 效率。在控制生产成本和工艺复杂程度的基础上，提高大尺寸光电二极管的内部电荷转移速度，具有重大的科研和商业价值。本发明拟在生产成本和工艺难度相对较低的前提下，设计一种提高内部电荷转移速度和光生电荷收集效率的光电二极管器件结构。
具体的，所述衬底101具有第一掺杂类型的掺杂。其中，第一掺杂类型可以为n型或p型，与之对应的，第二掺杂类型为p型或n型。本发明的实施例中，以第一掺杂类型为p型，第二掺杂类型为n型描述。
在一示例中，所述衬底101为硅衬底，在一具体示例中，使用低浓度硼掺杂的P型硅片作为衬底(p-)。
另外，作为示例，所述第一掺杂类型的衬底101，具有相对的第一面和第二面，该示例中，如图所示向上的表面作为第一面，用于基于该面在衬底101中制作其他的器件功能层。
作为示例，所述衬底101的俯视图中的形状可以是矩形，也可以为六边形、八边形、圆形等形状，但并不局限于此，可依据实际需求进行选择。
继续参见图4所示，本发明的光电二极管结构还包括功能掺杂区102，所述功能掺杂区102具有第二类型掺杂，本实施例中为n型掺杂，如n-掺杂。其中，所述功能掺杂区102为非均匀掺杂，基于上述设计，当光生载流子被收集到功能掺杂区102(如n-)后，基于非均匀掺杂的原因，此区域会形成与浓度分布相关的电势梯度，可以基于电势梯度控制载流子在该区域的传输情况，例如，可以是在该区域形成一个自建驱动电势，使得载流子向n+方向移动，可以理解的是，只要在功能掺杂区形成电势差能够产生驱动光生载流子朝向辅助掺杂区运动的效果即可。本发明的方式与均匀掺杂相比，能够大大提高载流子的运输速度。另外，该方法与外加电场的方法相比，工艺制造难度大大降低，且消除了部分实际使用场景的限制。
作为示例，所述功能掺杂区102的掺杂浓度分布方式包括线性分布、平方根分布中的任意一种。例如，对于线性分布可以是，如图4所示，如图中箭头方向，即朝向n+的方向，掺杂浓度线性增加。另外，在其他示例中，也可以是沿箭头方向，掺杂浓度以平方根的方式增加。当然，也可以是其他更复杂的函数分布关系，并不局限于此，线性和平方根分布只是比较典型形成电势梯度的掺杂分布，我们的方法理论上可以实现任意分布函数的掺杂。
作为示例，所述功能掺杂区102的俯视图中的形状可以是矩形，也可以为六边形、八边形、圆形等形状，但并不局限于此，可依据实际需求进行选择。
作为示例，所述功能掺杂区102位于所述衬底101中，自衬底101的第一面进行离子注入形成。在一具体示例中，使用非均匀掺杂的方法制造低浓度掺杂N型区域(n-)，n-区域的掺杂可以使用线性分布、平方根分布以及其他更复杂的函数分布。
继续参见图4所示，本发明的光电二极管结构还包括表面掺杂区103，所述第一掺杂类型的表面掺杂区103，形成在所述功能掺杂区102中，位于所述第一面一侧，且所述表面掺杂区103具有第二掺杂浓度。
作为示例，所述第二掺杂浓度大于所述第一掺杂浓度。另外，在一示例中，所述表面掺杂区103远离栅极结构的一端的边缘与功能掺杂区102的外缘对齐。
在一具体示例中，在低浓度掺杂N型区域上方沉积一层厚度较薄的重掺杂P型区域(p+)。
作为示例，所述表面掺杂区103的俯视图中的形状可以是矩形，也可以为六边形、八边形、圆形等形状，但并不局限于此，可依据实际需求进行选择。
继续参见图4所示，本发明的光电二极管结构还包括栅极结构104，位于所述衬底101的第一面上。其中，所述栅极结构104的制备工艺及材质均可以采用现有设计。
在一示例中，所述栅极结构104与所述功能掺杂区102相连接，即，所述栅极结构104靠近所述功能掺杂区102一侧的边缘与所述功能掺杂区102靠近栅极结构一侧的边缘相对齐，位于同一平面上，二者不重叠。当然，还可以是可以发挥本发明效果的其他位置关系。
继续参见图4所示，本发明的光电二极管结构还包括第二掺杂类型的辅助掺杂区105，连接所述栅极结构104与所述功能掺杂区102，所述辅助掺杂区105至少形成在所述功能掺杂区102中，位于所述第一面一侧，且所述辅助掺杂区105与所述表面掺杂区103之间具有间距，所述辅助掺杂区105的掺杂浓度大于所述功能掺杂区102的掺杂浓度，在一示例中，所述辅助掺杂区105的掺杂浓度大于所述功能掺杂区102任意位置的浓度，不在一个数量级。
另外，所示衬底(如p-衬底)，所述功能掺杂区(如n-掺杂区)，所述表面掺杂区(如p+掺杂区)以及所述辅助掺杂区(如n+掺杂区)这些区域的浓度不同工艺厂都会有差别，但实际上都是根据需求要跟工厂协商的，比如，在一示例中，p-在10 15～10 16cm -3；n-在10 15～10 16cm -3；n+在10 18～10 20cm -3；但这只是一个实例，只要掺杂浓度满足n-小于n就可以，n是硅片中本征载流子的浓度，其他依此类推。
作为示例，所述辅助掺杂区105的俯视图中的形状可以是矩形，也可以为六边形、八边形、圆形等形状，但并不局限于此，可依据实际需求进行选择。另外，在一示例中，所述辅助掺杂区105的靠近栅极结构一侧的边缘与功能掺杂区102靠近栅极结构一侧的边缘相对齐，二者共同，实现所述栅极结构104与所述辅助掺杂区105之间的相连接。
基于本发明的设计，所述表面掺杂区103、所述功能掺杂区102及所述衬底101形成PNP型的结构，使得光电二极管大部分区域在电路复位阶段完全耗尽，提升了光生载流子的收集效率。进一步，基于辅助掺杂区105的设计，光生载流子被收集到例如n-区域(所述功能掺 杂区102)后，由于非均匀掺杂的原因，此区域会形成与浓度分布相关的电势梯度，与均匀掺杂相比，能够大大提高载流子的运输速度。所述辅助掺杂区105还可以是作为器件的漏极结构，与栅极结构104以及源极结构106构成MOS器件。
例如，参见图7所示，基于本发明设计的一示例中，n-区域会形成指向n+区域方向的内建电势差，n-区域的光生载流子会在电势差的作用下，加速移动向n+区域。另外，在其过程中，所述表面掺杂区103还可以具有阻挡作用，由于表面p+区域(表面掺杂区103)的阻挡，扩散运动的趋势也被限制在水平方向，加快光生载流子移动的n+区域的速度。
在一示例中，所述衬底101、所述功能掺杂区102、所述表面掺杂区103以及所述辅助掺杂区105的上表面相平齐，所述功能掺杂区102的深度小于所述衬底101的深度，所述表面掺杂区103的深度小于所述功能掺杂区102的深度，所述辅助掺杂区105的深度小于所述功能区102的深度，进一步示例中，所述表面掺杂区103的深度等于所述辅助掺杂区105的深度。当然，在其他示例中，还可以依据实际需求选择合适的深度范围。
如图5-6所示，作为示例，所述表面掺杂区203及所述辅助掺杂区205的形状均包括环形，所述栅极结构204位于所述辅助掺杂区205构成环形结构内，且所述栅极结构204也呈环形设置，环形的所述栅极结构204内对应的所述功能掺杂区202中还形成有内部掺杂区，形成源极结构206，所述内部掺杂区与所述辅助掺杂区205的掺杂类型及掺杂浓度均相同。
具体的，所述辅助掺杂区105呈环状设置在栅极结构104的外围。其中，环状结构增加面积，如环状结构的n+区域，增大了接收电荷的面积，能更快地接收n-运输来的载流子，能进一步提升光生载流子的运输效率。在一具体示例中，在与传输栅极(TG)相连的环状小部分区域通过离子注入制造重掺杂N型区域(n+)，得到所述辅助掺杂区105。进一步示例中，所述栅极结构104、所述表面掺杂区103及所述辅助掺杂区105构成同心环。
作为示例，所述第一掺杂类型为p型，所述第二掺杂类型为n型，所述表面掺杂区、所述功能掺杂区及所述衬底形成PNP型结构。当然，第一和第二掺杂类型也可以互换。
另外，参见图7所示，结合前述结构中的描述进一步对光生载流子的传输过程进行进一步说明，以p-为轻型掺杂硅衬底，n+为重掺杂区，n-为非均匀低浓度掺杂区，p+为表面重掺杂区为例，图7显示为光生载流子的传输过程示意图，当二极管达到其复位电压时，大部分压降落在N型重掺杂区(n+)，N型低掺杂区(n-)完全耗尽，当有光信号输入时，光生载流子会快速被收集到n-区域。由于非均匀掺杂的缘故，n-区域会形成指向n+区域方向的内建电势差，n-区域的光生载流子会在电势差的作用下，加速移动向n-区域。此外由于表面p+区域的阻挡，扩散运动的趋势也被限制在水平方向，加快光生载流子移动的n+区域的速度。而 被收集到n+区域的载流子会直接通过运输门(TG)进入后续的电路。
如图1及图2-4所示，本发明还提供一种新型光电二极管结构的制备方法，其中，本发明实施例中上述所描述的新型光电二极管结构优选采用本发明该实施例中的制备方法制备得到，具体光电二极管结构以及制备方法中的描述可以相互参考，多余之处不再赘述。
下面将结合附图详细说明本发明的新型光电二极管结构的制备方法。需要说明的是，上述顺序并不严格代表本发明所保护的新型光电二极管结构的制备顺序，本领域技术人员可以依据实际工艺步骤进行改变，图1仅示出了一示例中的新型光电二极管结构的制备步骤。
首先，如图1中的S1及图2所示，提供第一掺杂类型的衬底101，具有相对的第一面和第二面，所述衬底101具有第一掺杂浓度。所述衬底101的特征可以参见在器件结构中的描述。其中，所述衬底101可以是全部掺杂得到的衬底结构，也可以是在初始衬底(如硅衬底)中进行一部分掺杂得到的一个掺杂区域，用于制备后续的器件结构层。
接着，如图1中的S2及图3所示，自所述第一面在所述衬底101中形成第二掺杂类型的功能掺杂区102，其中，所述功能掺杂区102的掺杂浓度分布为非均匀掺杂。
作为示例，所述功能掺杂区102可以是基于掩膜板进行离子注入形成。
作为示例，基于离子注入及注入离子扩散形成预设浓度分布的所述功能掺杂区102。其中，该示例中，基于离子注入和注入离子扩散两个阶段形成，即，提出一种掺杂非均匀分布实现理论，该理论可以指导设计出任何浓度分布函数的非均匀掺杂结构。其中，整个掺杂过程分为离子注入和扩散两个阶段，分别介绍如下：
在所述离子注入阶段：
设定离子注入能量D及离子注入浓度C 0。离子注入过程完成的时间很短，主要关注的参数是注入能量以及注入浓度。在工艺上设定好注入能量可以得到某杂质在硅中的平均射程R A，这个纵向深度的值对应注入后的最大浓度，这个值约等于注入时的浓度，而以平均射程所在的点，杂质浓度在纵向上的分布可近似取高斯函数形式，将峰值下降一半改变的深度记为ΔR A，可以得到纵向的浓度分布函数为：
Figure PCTCN2021104240-appb-000008
基于上述方式，C y代表注入方向上的浓度，y代表注入方向上的位置，可以通过离子注入能量D及离子注入浓度C 0得到注入后纵向任意位置的离子掺杂浓度。
在所述注入离子扩散阶段：
将离子注入阶段结束的一瞬间作为扩散过程的起点，本实施例以C 0为注入点进行说明， 由于不再有外力干扰，所以扩散源唯一且不随时间变化，则可以建立整个扩散过程的齐次微分方程：
Figure PCTCN2021104240-appb-000009
其中，x代表与离子注入点之间的距离，t代表扩散时间，C代表浓度，d表征扩散系数，C(x,t＝0)代表扩散开始时的浓度分布，f(x)是扩散开始时的浓度分布函数，其中，d是为了求解数学方程更便捷而写成平方的形式，此处d 2＝D，但建立原始扩散方程时不知道实际好观测的是D，此式更具有普适性。
接着，由于硅的晶系是各向同性的，假设扩散系数D不随位置发生变化，又由注入浓度C 0确定边界条件，上式在实际分析时可写成：
Figure PCTCN2021104240-appb-000010
继续，解常微分方程后，假设注入点位置为x 0，可得到其状态概率密度：
Figure PCTCN2021104240-appb-000011
其中，C(x,t)代表扩散t时间时x位置的掺杂浓度。另外，
Figure PCTCN2021104240-appb-000012
在实际中为向单一个方向的扩散长度，令
Figure PCTCN2021104240-appb-000013
为扩散过程的特征长度，表征一维方向上的扩散距离；此外，实际过程中离子注入一般为一个掩膜缺口而非一个点，将x 0这个点向两边分拓宽w，w表征掩膜开口的宽度，代表实际相应的掩膜缺口的宽度为2w，则上面的公式可以表示为：
Figure PCTCN2021104240-appb-000014
基于上述方式，每一个实际的物理量在公式中都有了对应，可以得到任意时间任意位置对应的掺杂浓度。其中，第一阶段离子注入的分析是近似纵向的一条线的分布，不考虑形成正态分布的过程横向的扩散，实际上由于时间很短，这个近似是有效的，每个点对应一个浓度，这个浓度就是第二阶段公式中的C 0，也就是扩散过程的初始浓度；第二阶段公式计算出来的就是最终浓度分布。
另外，对于任意的非均匀掺杂，给出其分布函数C(x)，可以用不同间距的n个掩膜开口进行一次离子注入，由公式物理量的定义，每个掩膜口对应的特征长度
Figure PCTCN2021104240-appb-000015
其中，x1 是第一个掩膜开口的中心位置，xn是最后一个掩膜开口的中心位置，第i个掩膜开口的宽度
Figure PCTCN2021104240-appb-000016
掩膜开口确定公式，把积分近似为求和，则有：
Figure PCTCN2021104240-appb-000017
基于上述方式，该公式可以理解为无限个掩膜开口出来的就是和给定掺杂分布函数完全一样，该计算方式普适性很高，可以根据实际需求决定开多少个掩膜开口，越多越精确，一般100微米的器件开十个口做线性非均匀掺杂就已经非常精确。
作为示例，如图8所示，在所述衬底101上制作掩膜板301，基于所述掩膜板进行离子注入形成所述功能掺杂区102，所述掩膜板中形成有若干个套置的环形掩膜板开口301a，其中，所述环形开口的尺寸依据开口对应位置的浓度设置。
例如，在一具体示例中，本发明提出了一种新型环状结构非均匀掺杂区域(n-)实现方法，其结构示意图如图8所示，对于n-的非均匀掺杂区域，针对不同的应用环境可以采用多种不同掺杂的方式，本发明采用沉积氧化物的方式制造掩膜，将待掺杂区域分成多段，每段具有独立掩膜，通过合理设置掩膜尺寸，然后进行一次离子注入，再结合较长时间的扩散，来实现任意分布的非均匀掺杂，实际扩散时间可以基于计算出的特征长度L确定，可以在此基础上略有延长，可以依据实际需求设定。
接着，如图1中的S3及图4所示，自所述第一面在所述功能掺杂区102中形成第一掺杂类型的表面掺杂区103，且所述表面掺杂区具有第二掺杂浓度，可以采用现有方式进行掺杂。
接着，如图1中的S4及图4所示，在所述衬底101的第一面上形成栅极结构104。
最后，如图1中的S5及图4所示，自所述第一面在所述功能掺杂区102形成第二掺杂类型的辅助掺杂区105，所述辅助掺杂区105连接所述栅极结构104与所述功能掺杂区102，且所述辅助掺杂区105与所述表面掺杂区103之间具有间距，所述辅助掺杂区105的掺杂浓度大于所述功能掺杂区102的掺杂浓度。
另外，如图9所示，本发明还提供一种采用如上述方案中任意一项所述的新型光电二极管结构的电路结构，所述电路结构包括：
所述新型光电二极管结构100，所述表面掺杂区103接地；
电荷接收模块400，与漏极结构电连接，其中，可以是辅助掺杂区作为所述漏极结构，在复位期间接收存储在所述所述新型光电二极管结构中的电荷，包括积分电容器及控制开关；
放大模块500，两输入端分别与比较电压及所述漏极结构电连接，并将放大的信号输出， 包括电荷放大器及控制开关。另外，电荷放大器的输出端与积分电容器的一端相连接，还进一步连接像素的列输出。
其中，图9显示为本发明新型光电二极管结构应用到一个双增益像素中的电路示意图，当二极管达到其复位电压时，大部分压降落在N型重掺杂区(n+)，即所述辅助掺杂区105，而低掺杂区完全耗尽。电子被收集在N型低掺杂区(n-)，即所述功能掺杂区102，并在梯度电势的作用下快速转移至N型重掺杂区(n+)。在复位期间，TG(栅极结构)导通，存储在光电二极管上的电荷将移动到积分电容器C1/C2。
另外，在像素输出上测量的噪声与复位操作相关联：
Figure PCTCN2021104240-appb-000018
其中，C 二极管(VREF)是电压在VREF处的电容，K是玻尔兹曼常数，K＝1.38×10 -23m 2kgs -2K -1，T代表温度。由于使用本发明的二极管结构，这个值相对很小，这意味着像素噪声的基底也会很小，进一步能够提升成像效果。本发明提出了一种光电二极管器件理论、结构及实现方法，与现有技术相比，在降低了工业制造难度和制造成本的基础上，提高了大尺寸光电二极管中电荷的转移速度和收集效率，能够降低暗电流产生的噪声。
综上所述，本发明的新型光电二极管结构、制备方法及电路结构，通过形成非均匀掺杂的功能掺杂区，从而在功能掺杂区中形成自建电势差，可以驱动光剩载流子的运动方向，如可以使光生载流子会在电势差的作用下加速移动，使得被收集的载流子会直接通过运输门(TG)进入后续的电路。另外，环状结构的辅助掺杂区可以增大接收电荷的面积，能更快地接收运输来的载流子，能进一步提升光生载流子的运输效率。所以，本发明有效克服了现有技术中的种种缺点而具高度产业利用价值。
上述实施例仅例示性说明本发明的原理及其功效，而非用于限制本发明。任何熟悉此技术的人士皆可在不违背本发明的精神及范畴下，对上述实施例进行修饰或改变。因此，举凡所属技术领域中具有通常知识者在未脱离本发明所揭示的精神与技术思想下所完成的一切等效修饰或改变，仍应由本发明的权利要求所涵盖。

Claims (11)

  1. 一种新型光电二极管结构，其特征在于，所述光电二极管结构包括：
    第一掺杂类型的衬底，所述衬底具有第一掺杂浓度；
    第二掺杂类型的功能掺杂区，形成在所述衬底中，所述功能掺杂区的掺杂浓度分布为非均匀掺杂，以在所述功能掺杂区形成电势梯度；
    第一掺杂类型的表面掺杂区，自所述功能掺杂区的上表面形成在所述功能掺杂区中，且所述表面掺杂区具有第二掺杂浓度；
    栅极结构，位于所述衬底上；以及
    第二掺杂类型的辅助掺杂区，形成在所述功能掺杂区中，并连接所述栅极结构与所述功能掺杂区，且所述辅助掺杂区与所述表面掺杂区之间具有间距，所述辅助掺杂区的掺杂浓度大于所述功能掺杂区的掺杂浓度。
  2. 根据权利要求1所述的新型光电二极管结构，其特征在于，所述表面掺杂区及所述辅助掺杂区的形状均包括环形，所述栅极结构位于所述辅助掺杂区构成环形结构内，且所述栅极结构呈环形设置，环形的所述栅极结构内对应的所述功能掺杂区中还形成有内部掺杂区，所述内部掺杂区与所述辅助掺杂区的掺杂类型及掺杂浓度均相同。
  3. 根据权利要求1所述的新型光电二极管结构，其特征在于，所述第一掺杂类型为p型，所述第二掺杂类型为n型，所述表面掺杂区、所述功能掺杂区及所述衬底形成PNP型结构。
  4. 根据权利要求1-3中任意一项所述的新型光电二极管结构，其特征在于，所述功能掺杂区的掺杂浓度分布方式包括线性分布、平方根分布中的任意一种。
  5. 一种新型光电二极管结构的制备方法，其特征在于，所述制备方法包括如下步骤：
    提供第一掺杂类型的衬底，具有相对的第一面和第二面，所述衬底具有第一掺杂浓度；
    自所述第一面在所述衬底中形成第二掺杂类型的功能掺杂区，其中，所述功能掺杂区的掺杂浓度分布为非均匀掺杂，以在所述功能掺杂区形成电势梯度；
    自所述第一面在所述功能掺杂区中形成第一掺杂类型的表面掺杂区，且所述表面掺杂区具有第二掺杂浓度；
    在所述衬底的第一面上形成栅极结构；以及
    自所述第一面在所述功能掺杂区形成第二掺杂类型的辅助掺杂区，所述辅助掺杂区连接所述栅极结构与所述功能掺杂区，且所述辅助掺杂区与所述表面掺杂区之间具有间距， 所述辅助掺杂区的掺杂浓度大于所述功能掺杂区的掺杂浓度。
  6. 根据权利要求5所述的新型光电二极管结构的制备方法，其特征在于，基于离子注入及注入离子扩散形成预设浓度分布的所述功能掺杂区。
  7. 根据权利要求6所述的新型光电二极管结构的制备方法，其特征在于，基于所述离子注入形成所述功能掺杂区的步骤包括：离子注入后所述功能掺杂区的浓度分布为：
    Figure PCTCN2021104240-appb-100001
    其中，R A为杂质在衬底中的平均射程且与所述注入能量对应，并在注入方向上对应掺杂浓度峰值，ΔR A为掺杂浓度峰值下降一半所改变的深度，C y代表注入方向上的浓度；y代表注入方向上的位置，C 0代表注入离子浓度。
  8. 根据权利要求7所述的新型光电二极管结构的制备方法，其特征在于，基于所述注入离子扩散形成所述功能掺杂区的步骤包括：
    Figure PCTCN2021104240-appb-100002
    其中，x0代表离子注入点，x代表与离子注入点之间的距离，
    Figure PCTCN2021104240-appb-100003
    为扩散过程的特征长度，D为扩散系数，w为将x 0点向两边分别拓宽的距离，C(x,t)为扩散时间t时x位置的浓度。
  9. 根据权利要求5-8中任意一项所述的新型光电二极管结构的制备方法，其特征在于，在所述衬底上制作掩膜板，基于所述掩膜板进行离子注入形成所述功能掺杂区，所述掩膜板中形成有若干个套置的环形开口，其中，所述环形开口的尺寸依据开口对应位置的浓度设置，设置方式包括：
    Figure PCTCN2021104240-appb-100004
    其中，C 0代表注入离子浓度，xi代表第i个掩膜开口的中心位置，l代表每个掩膜开口下扩散过程的特征长度，
    Figure PCTCN2021104240-appb-100005
    wi代表第i个掩膜开口的宽度
    Figure PCTCN2021104240-appb-100006
    C(x)代表x方向上的浓度分布函数。
  10. 一种包括如权利要求1-4中任意一项所述的新型光电二极管结构的电路结构，其特征在于，所述电路结构包括：
    所述新型光电二极管结构，所述表面掺杂区接地；
    电荷接收模块，与新型光电二极管结构的漏极结构电连接，在复位期间接收存储在所述所述新型光电二极管结构中的电荷，所述电荷接收模块包括积分电容器及控制开关；
    放大模块，两输入端分别与比较电压及所述漏极结构电连接，输出端将放大的信号输出，所述放大模块包括电荷放大器及控制开关。
  11. 根据权利要求10所述的电路结构，其特征在于，所述放大模块的输出端与像素列输出相连，在像素输出上的噪声为：
    Figure PCTCN2021104240-appb-100007
    其中，K是玻尔兹曼常数，T代表温度，C 二极管(VREF)是电压在VREF处的电容。
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