WO2021042626A1 - 一种紫外探测器及其制备方法 - Google Patents

一种紫外探测器及其制备方法 Download PDF

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WO2021042626A1
WO2021042626A1 PCT/CN2019/126518 CN2019126518W WO2021042626A1 WO 2021042626 A1 WO2021042626 A1 WO 2021042626A1 CN 2019126518 W CN2019126518 W CN 2019126518W WO 2021042626 A1 WO2021042626 A1 WO 2021042626A1
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layer
epitaxial layer
epitaxial
ohmic contact
ultraviolet detector
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PCT/CN2019/126518
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English (en)
French (fr)
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周幸叶
谭鑫
吕元杰
王元刚
宋旭波
梁士雄
冯志红
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中国电子科技集团公司第十三研究所
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Publication of WO2021042626A1 publication Critical patent/WO2021042626A1/zh
Priority to US17/684,999 priority Critical patent/US20220190175A1/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
    • H01L31/035281—Shape of the body
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    • 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
    • H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes
    • H01L31/1075—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes in which the active layers, e.g. absorption or multiplication layers, form an heterostructure, e.g. SAM structure
    • 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
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H—ELECTRICITY
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    • 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
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022416—Electrodes for devices characterised by at least one potential jump barrier or surface barrier comprising ring electrodes
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    • 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
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • H—ELECTRICITY
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    • 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
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • H01L31/1812—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table including only AIVBIV alloys, e.g. SiGe
    • H—ELECTRICITY
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    • 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
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier 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
    • H01L31/0248—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
    • H01L31/0256—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 the material
    • H01L31/0264—Inorganic materials
    • H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
    • H—ELECTRICITY
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    • 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
    • H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes

Definitions

  • This application belongs to the field of semiconductor technology, and in particular relates to an ultraviolet detector and a preparation method thereof.
  • 4H-SiC avalanche photodiode ultraviolet detectors have the advantages of high gain, high responsivity, and low dark current. UV signal and even UV single photon detection.
  • UV detectors there are two types of UV detectors, back-side incident type and front-side incident type.
  • the back-side incident type ultraviolet detectors will greatly reduce the quantum efficiency of the detector due to the absorption of photons by the substrate; while the traditional front-side incident type ultraviolet detectors will greatly reduce the quantum efficiency of the detector. Due to the presence of the heavily doped ohmic contact layer on the top layer of the UV detector, a large number of short-wavelength photons will be absorbed by the ohmic contact layer, thereby reducing the quantum efficiency.
  • the present application provides an ultraviolet detector and a preparation method thereof to solve the problem of low quantum efficiency of ultraviolet detectors in the prior art.
  • the first aspect of the embodiments of the present application provides an ultraviolet detector, which includes:
  • a first epitaxial layer located on the substrate, and the first epitaxial layer is a heavily doped epitaxial layer
  • the second epitaxial layer is located on the first epitaxial layer, the second epitaxial layer is a lightly doped epitaxial layer, or the second epitaxial layer is composed of at least one lightly doped epitaxial layer and at least one heavy layer. Double-layer or multi-layer structure composed of doped epitaxial layers;
  • the ohmic contact layer is located on the second epitaxial layer or formed in the second epitaxial layer, and the ohmic contact layer is a patterned heavily doped layer; wherein, the ohmic contact layer is formed on the second epitaxial layer.
  • the upper surface of the ohmic contact layer is not lower than the upper surface of the second epitaxial layer, and the lower surface of the ohmic contact layer is higher than the lower surface of the second epitaxial layer;
  • the first metal electrode layer is located on the ohmic contact layer.
  • the first epitaxial layer is a P-type silicon carbide epitaxial layer
  • the second epitaxial layer is an N-type silicon carbide epitaxial layer
  • the ohmic contact layer is N Type ohmic contact layer
  • the first epitaxial layer is an N-type silicon carbide epitaxial layer
  • the second epitaxial layer is a P-type silicon carbide epitaxial layer
  • the ohmic contact layer is a P-type ohmic contact layer.
  • the surface area of the first metal electrode layer is not greater than the surface area of the ohmic contact layer, and the first metal The surface shape of the electrode layer corresponds to the surface pattern of the ohmic contact layer.
  • the surface pattern of the ohmic contact layer includes any one of a circular ring shape, a square ring shape, a window shape, and an array shape.
  • the ultraviolet detector further includes a passivation protection layer, and the passivation protection layer covers the first aspect.
  • the area of the second epitaxial layer is smaller than the area of the first epitaxial layer, and the area on the first epitaxial layer A partial area and the second epitaxial layer form an isolation mesa, wherein the partial area represents an area on the first epitaxial layer with the second epitaxial layer;
  • the ultraviolet detector further includes a second metal electrode layer, and the second metal electrode layer is formed in an area outside the isolation mesa on the first epitaxial layer.
  • the substrate is a heavily doped substrate
  • the ultraviolet detector further includes a second metal electrode layer, and the second metal electrode layer is located on the other side of the substrate opposite to the side of the substrate where the first epitaxial layer is formed.
  • the second aspect of the embodiments of the present application provides a preparation method of an ultraviolet detector, the preparation method including:
  • first semiconductor epitaxial wafer or a second semiconductor epitaxial wafer wherein the first semiconductor epitaxial wafer includes a substrate, a first epitaxial layer and a second epitaxial layer in order from bottom to top; the second semiconductor epitaxial wafer is from bottom to top It includes a substrate, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer in sequence; wherein, the first epitaxial layer is a heavily doped epitaxial layer; the second epitaxial layer is a lightly doped epitaxial layer, or, The second epitaxial layer is a double-layer or multi-layer structure composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer; the third epitaxial layer is a heavily doped epitaxial layer;
  • a mask layer is prepared on the surface of the second epitaxial layer, and photoresist is coated on the mask layer and photolithography is performed to form a patterned ion implantation window. Ion implantation through the ion implantation window to form a patterned ohmic contact layer;
  • a mask layer is prepared on the surface of the third epitaxial layer, photoresist is coated on the mask layer and photolithography is performed to form a patterned etching window, and the mask is The area outside the etching window on the film layer is etched to the second epitaxial layer to form a patterned ohmic contact layer;
  • a metal is vapor-deposited on the active area and annealed to form a first metal electrode layer.
  • the method further includes:
  • a passivation protection layer is deposited on the surface of the first semiconductor epitaxial wafer or the second semiconductor epitaxial wafer, and an electrode window is etched.
  • the first epitaxial layer is a P-type silicon carbide epitaxial layer
  • the second epitaxial layer is an N-type carbide A silicon epitaxial layer
  • the ohmic contact layer is an N-type ohmic contact layer
  • the first epitaxial layer is an N-type silicon carbide epitaxial layer
  • the second epitaxial layer is a P-type silicon carbide epitaxial layer
  • the ohmic contact layer is a P-type ohmic contact layer.
  • the present application has the beneficial effect that the ultraviolet detector provided in the present application includes a detector epitaxial structure composed of a first epitaxial layer, a second epitaxial layer and a patterned ohmic contact layer, wherein the second The epitaxial layer is the absorption multiplication area of the ultraviolet detector.
  • the ultraviolet detector provided in the present application includes a detector epitaxial structure composed of a first epitaxial layer, a second epitaxial layer and a patterned ohmic contact layer, wherein the second The epitaxial layer is the absorption multiplication area of the ultraviolet detector.
  • FIG. 1 is a schematic diagram of a structure of an ohmic contact layer in an ultraviolet detector in the prior art provided by an embodiment of the present application;
  • FIG. 2 is a schematic structural diagram of an ultraviolet detector provided by an embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of another ultraviolet detector provided by an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of another ultraviolet detector provided by an embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of still another ultraviolet detector provided by an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an active area surface of an ultraviolet detector provided by an embodiment of the present application.
  • FIG. 7 is a schematic diagram of the surface of the second active area of the ultraviolet detector provided by the embodiment of the present application.
  • FIG. 8 is a schematic diagram of the surface of the third active area of the ultraviolet detector provided by the embodiment of the present application.
  • FIG. 9 is a schematic diagram of the surface of the fourth active area of the ultraviolet detector provided by the embodiment of the present application.
  • FIG. 10 is a schematic diagram of the surface of the fifth active area of the ultraviolet detector provided by the embodiment of the present application.
  • FIG. 11 is a schematic diagram of the surface of the sixth active area of the ultraviolet detector provided by the embodiment of the present application.
  • the ultraviolet detector provided by it includes from bottom to top: a substrate 10, a first epitaxial layer 11, The second epitaxial layer 12 and the ohmic contact layer 13. It can be seen that the ohmic contact layer 13 completely covers the upper part of the second epitaxial layer 12.
  • the ohmic contact layer 13 will absorb the incident photons, reducing the number of photons reaching the second epitaxial layer 12. The number of photons (absorption multiplication zone), which will cause the quantum efficiency of the UV detector to decrease.
  • the ohmic contact layer is a patterned structure, and the patterned ohmic contact layer shields the second epitaxial layer below the second epitaxial layer, thereby reducing the absorption of incident photons by the ohmic contact layer , Improve quantum efficiency.
  • FIG. 2 is a schematic structural diagram (cross-sectional view) of an ultraviolet detector provided by an embodiment of the present application.
  • the ohmic contact layer is formed in the second epitaxial layer.
  • the ultraviolet detector provided includes: The substrate 10, the first epitaxial layer 11, the second epitaxial layer 12, the ohmic contact layer 13 formed in the second epitaxial layer 12, and the first metal electrode layer 14 located on the ohmic contact layer 13.
  • the surface shape of the ohmic contact layer 13 is annular.
  • the substrate may be any one of materials such as silicon, sapphire, gallium nitride, or silicon carbide.
  • the upper surface of the ohmic contact layer 13 may be level with the upper surface of the second epitaxial layer 12.
  • the ohmic contact layer 13 is formed in the second epitaxial layer 12.
  • the upper surface of the ohmic contact layer 13 may not be lower than the upper surface of the second epitaxial layer 12, and the lower surface of the ohmic contact layer 13 needs to be higher than The bottom surface of the second epitaxial layer 12.
  • the first epitaxial layer 11, the second epitaxial layer 12, and the ohmic contact layer 13 can jointly form the detector epitaxial structure.
  • the first epitaxial layer 11 is a heavily doped epitaxial layer
  • the second epitaxial layer 12 is a lightly doped epitaxial layer.
  • the second epitaxial layer is a double-layer or multi-layer structure composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer; the ohmic contact layer 13 is a patterned heavily doped epitaxial layer
  • the ultraviolet detector adopts a frontal incident mode.
  • the entire second epitaxial layer 12 can be a lightly doped epitaxial layer, which is the absorption multiplier region of the ultraviolet detector; the second epitaxial layer 12 can also be composed of at least one layer A double-layer or multi-layer structure composed of a lightly doped epitaxial layer and at least one heavily doped epitaxial layer, that is, a structure in which the absorption layer and the multiplication layer are separated.
  • the surface area of the first metal electrode layer 14 on the ohmic contact layer 13 is not greater than the surface area of the ohmic contact layer 13.
  • the doping concentration of the ohmic contact layer 13 may be between 1 ⁇ 10 18 cm -3 and 1 ⁇ 10 20 cm -3 , and the depth may be between 0.01 and 0.5 ⁇ m.
  • the doping concentration of the first epitaxial layer 11 may be between 1 ⁇ 10 18 cm -3 and 1 ⁇ 10 20 cm -3 , and the thickness may be between 1 and 3 ⁇ m.
  • the second epitaxial layer 12 is a lightly doped single epitaxial layer, its doping concentration can be between 1 ⁇ 10 15 cm -3 and 1 ⁇ 10 17 cm -3 ; if the second epitaxial layer 12 is composed of at least one layer
  • the lightly doped epitaxial layer and at least one heavily doped epitaxial layer constitute a double-layer or multi-layer structure.
  • the concentration of the lightly doped epitaxial layer can be between 1 ⁇ 10 15 cm -3 and 1 ⁇ 10 17 cm -3
  • the heavy doping concentration may be between 5 ⁇ 10 17 cm -3 and 1 ⁇ 10 20 cm -3
  • the total thickness of the second epitaxial layer 12 may be between 0.1 and 50 ⁇ m. .
  • the ultraviolet detector may further include a passivation protective layer to suppress the surface leakage of the ultraviolet detector and reduce the dark current.
  • the passivation protection layer 15 may cover the area on the outer surface of the second epitaxial layer 12 except for the first metal electrode layer 14.
  • the passivation protection layer may be one or any combination of SiO 2 , Al 2 O 3 , HfO 2 , Y 2 O 3 , and SiN x materials, and the thickness may be between 50 nm and 10 ⁇ m.
  • the area of the second epitaxial layer 12 may be smaller than the area of the first epitaxial layer 11, and a part of the area on the first epitaxial layer 11 forms an isolation from the second epitaxial layer 12.
  • the mesa (the upper surface of the isolation mesa is the active area of the ultraviolet detector, and the ohmic contact layer 13 is located in the active area).
  • the partial area on the first epitaxial layer 11 refers to the second epitaxial layer 11 formed on the second epitaxial layer. Layer 12 area.
  • the isolation mesa can be a vertical structure with an inclination angle of 90 degrees, or a mesa structure with a non-vertical inclination angle.
  • the ultraviolet detector further includes a second metal electrode layer 16, and the second metal electrode layer 16 is formed on the first epitaxial layer 11 in an area outside the isolation mesa, for example Can be distributed around the outside of the isolation table.
  • the second metal electrode layer 16 may also be located on the other side of the substrate 10, and the other side is opposite to the side of the substrate 10 on which the first epitaxial layer 11 is formed.
  • the epitaxial layer 11 may be located on the side above the substrate 10, and the second metal electrode layer 16 may be located on the side below the substrate 10.
  • the substrate needs to be a heavily doped substrate.
  • the first epitaxial layer may be a P-type silicon carbide epitaxial layer
  • the second epitaxial layer may be an N-type silicon carbide epitaxial layer
  • the ohmic contact layer may be an N-type ohmic contact layer.
  • the first epitaxial layer may be an N-type silicon carbide epitaxial layer.
  • One metal electrode layer is the cathode metal electrode layer, which can be electrically connected to the N-type ohmic contact layer; the second metal electrode layer is the anode metal electrode layer, which can be connected to the first epitaxial layer (P-type silicon carbide epitaxial layer) An electrical connection is formed, and the first epitaxial layer, the second epitaxial layer and the ohmic contact layer form the detector epitaxial structure.
  • the first epitaxial layer may be an N-type silicon carbide epitaxial layer
  • the second epitaxial layer may be a P-type silicon carbide epitaxial layer
  • the ohmic contact layer may be a P-type ohmic contact layer.
  • the first epitaxial layer may be a P-type silicon carbide epitaxial layer.
  • One metal electrode layer is the anode metal electrode layer, which can be electrically connected to the P-type ohmic contact layer; the second metal electrode layer is the cathode metal electrode layer, which can be connected to the first epitaxial layer (N-type silicon carbide epitaxial layer) An electrical connection is formed, and the first epitaxial layer, the second epitaxial layer and the ohmic contact layer form the detector epitaxial structure.
  • P-type and N-type are used to represent different semiconductor materials, respectively, P-type represents a hole-type semiconductor, and N-type represents an electronic-type semiconductor.
  • the ultraviolet detector of the embodiment shown in FIG. 2 can be obtained by the following preparation method:
  • first semiconductor epitaxial wafer wherein the first semiconductor epitaxial wafer includes a substrate, a first epitaxial layer and a second epitaxial layer in order from bottom to top, wherein the first epitaxial layer is a heavily doped epitaxial layer;
  • the second epitaxial layer is a lightly doped epitaxial layer, or, the second epitaxial layer is a double-layer or multi-layer structure composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer;
  • the third epitaxial layer is a heavily doped epitaxial layer;
  • the metal is vapor-deposited and annealed in the active area to form a first metal electrode layer.
  • the above-mentioned preparation method may further include the step of preparing a passivation protection layer: after evaporating metal on the active area and annealing to form a first metal electrode layer, on the surface of the first semiconductor epitaxial wafer A passivation protective layer is deposited and the electrode window is etched.
  • the ultraviolet detector provided in this application includes a detector epitaxial structure composed of a first epitaxial layer, a second epitaxial layer and a patterned ohmic contact layer, wherein the second epitaxial layer is the absorption multiplication region of the ultraviolet detector
  • the absorption of incident photons by the patterned ohmic contact layer is greatly reduced, especially the absorption of short-wavelength photons by the ohmic contact layer. Therefore, the amount of incident photons reaching the absorption multiplication region will be greatly increased, thereby achieving the purpose of improving the quantum efficiency of the ultraviolet detector.
  • FIG. 3 is a schematic structural diagram (cross-sectional view) of another ultraviolet detector provided by an embodiment of the present application.
  • the difference from the embodiment shown in FIG. 2 is that the ohmic contact layer of the ultraviolet detector in the embodiment shown in FIG. 13 is located on the second epitaxial layer 12.
  • the ultraviolet detector can be obtained by the following preparation method:
  • the second semiconductor epitaxial wafer includes a substrate, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer from bottom to top; wherein, the first epitaxial layer is heavily doped Heteroepitaxial layer; the second epitaxial layer is a lightly doped epitaxial layer, or, the second epitaxial layer is a double layer or multiple layers composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer Layer structure; the third epitaxial layer is a heavily doped epitaxial layer;
  • a mask layer is prepared on the surface of the third epitaxial layer, photoresist is coated on the mask layer and photolithography is performed to form a patterned etching window, and one of the etching windows on the mask layer The outer area is etched to the second epitaxial layer to form a patterned ohmic contact layer;
  • a metal is vapor-deposited on the active area and annealed to form a first metal electrode layer.
  • the preparation method may further include the step of preparing a passivation protection layer: after evaporating metal on the active area and annealing to form the first metal electrode layer, on the surface of the second semiconductor epitaxial wafer A passivation protective layer is deposited and the electrode window is etched.
  • the ultraviolet detectors provided by the embodiments shown in FIGS. 2 and 3 adopt a mesa isolation method, and the active area is the isolation mesa of the ultraviolet detector.
  • FIG. 4 is a schematic structural diagram (cross-sectional view) of another ultraviolet detector provided by an embodiment of the present application. Compared with the embodiment shown in FIG. 2 and FIG. 3, the ultraviolet detector in the embodiment shown in FIG. 4 adopts The method of ion implantation realizes the isolation of the active area without making an isolation mesa.
  • the ohmic contact layer is formed in the second epitaxial layer (refer to the embodiment shown in FIG. 2, which will not be repeated here).
  • the substrate 10 may be a heavily doped substrate, and the second metal electrode layer 16 may be located on the other side of the substrate 10, and the other side of the substrate 10 is formed with the first epitaxial layer 11.
  • One side is opposite; that is, the first epitaxial layer 11 may be located on the side above the substrate 10, and the second metal electrode layer 16 may be located on the side below the substrate 10.
  • first semiconductor epitaxial wafer wherein the first semiconductor epitaxial wafer includes a substrate, a first epitaxial layer and a second epitaxial layer in order from bottom to top, wherein the first epitaxial layer is a heavily doped epitaxial layer;
  • the second epitaxial layer is a lightly doped epitaxial layer, or, the second epitaxial layer is a double-layer or multi-layer structure composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer;
  • the third epitaxial layer is a heavily doped epitaxial layer;
  • Ion implantation is used for isolation to form an active area
  • the metal is vapor-deposited and annealed in the active area to form a first metal electrode layer.
  • the preparation method may further include the step of preparing a passivation protection layer: after evaporating metal in the active area and annealing to form a first metal electrode layer, depositing a passivation protection layer on the surface of the first semiconductor epitaxial wafer, and The electrode window is etched out.
  • the preparation method may further include the step of preparing a second metal electrode layer: evaporate metal on the other side of the substrate and anneal to form a second metal electrode layer, and the other side is opposite to the side on which the first epitaxial layer is formed. .
  • FIG. 5 is a schematic structural diagram of another ultraviolet detector provided by an embodiment of the present application. It uses ion implantation to isolate the active region from the embodiment shown in FIG. 4, without making an isolation mesa.
  • the ohmic contact layer is located on the second epitaxial layer (refer to the embodiment shown in FIG. 2, which will not be repeated here).
  • the substrate 10 may be a heavily doped substrate, and the second metal electrode layer 16 may be located on the other side of the substrate 10, and the other side of the substrate 10 with the first epitaxial layer 11 formed One side is opposite; that is, the first epitaxial layer 11 may be located on the side above the substrate 10, and the second metal electrode layer 16 may be located on the side below the substrate 10.
  • the preparation method is as follows:
  • the second semiconductor epitaxial wafer includes a substrate, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer from bottom to top; wherein, the first epitaxial layer is heavily doped Heteroepitaxial layer; the second epitaxial layer is a lightly doped epitaxial layer, or, the second epitaxial layer is a double layer or multiple layers composed of at least one lightly doped epitaxial layer and at least one heavily doped epitaxial layer Layer structure; the third epitaxial layer is a heavily doped epitaxial layer;
  • a mask layer is prepared on the surface of the third epitaxial layer, photoresist is coated on the mask layer and photolithography is performed to form a patterned etching window, and one of the etching windows on the mask layer The outer area is etched to the second epitaxial layer to form a patterned ohmic contact layer;
  • Ion implantation is used for isolation to form an active area
  • a metal is vapor-deposited on the active area and annealed to form a first metal electrode layer.
  • the preparation method may further include the step of preparing a passivation protection layer: after evaporating metal on the active area and annealing to form the first metal electrode layer, on the surface of the second semiconductor epitaxial wafer A passivation protective layer is deposited and the electrode window is etched.
  • the preparation method may further include the step of preparing a second metal electrode layer: evaporate metal on the other side of the substrate and anneal to form a second metal electrode layer, and the other side is opposite to the side on which the first epitaxial layer is formed. .
  • the surface pattern of the ohmic contact layer 13 can be circular, square, window or array shape, and the surface pattern of the ohmic contact layer 13 can also be other shapes, as long as it has the ability to allow incident photons to pass directly through.
  • the patterned gap can be used.
  • the surface shape of the first metal electrode layer 14 may correspond to the surface pattern of the ohmic contact layer 13.
  • the surface of the first metal electrode layer 14 The shape can also be correspondingly circular.
  • FIGS 6-11 are schematic diagrams (top views) respectively showing six patterns on the surface of the active area of the ultraviolet detector.
  • the active area is circular (it may be a circular mesa active area formed by mesa etching, or it may be a circular active area formed by ion implantation), and its ohmic contact layer 13
  • the surface shape of the first metal electrode layer 14 is a circular ring (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer), and the surface shape of the first metal electrode layer 14 is also a circular ring The shape is formed on the ohmic contact layer 13.
  • the active area is rectangular (it can be a rectangle with rounded corners) (it can be a rectangular mesa active area formed by mesa etching, or a rectangular active area formed by ion implantation).
  • the surface shape of the ohmic contact layer 13 is a rectangular ring shape (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer), and the surface shape of the first metal electrode layer 14 It is also a rectangular ring shape and is formed on the ohmic contact layer 13.
  • the active area is circular (it can be a circular mesa active area formed by mesa etching, or it can be a circular active area formed by ion implantation), and its ohmic contact layer 13
  • the surface shape of the first metal electrode layer 14 is round window shape (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer), and the surface shape of the first metal electrode layer 14 has a cross inside.
  • the round window shape of the connected area is formed on the ohmic contact layer 13.
  • the active area is rectangular (it can be a rectangle with rounded corners) (it can be a rectangular mesa active area formed by mesa etching, or a rectangular active area formed by ion implantation).
  • the surface shape of the ohmic contact layer 13 is a rectangular window shape (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer), and the surface shape of the first metal electrode layer 14 It is also in the shape of a rectangular window with a cross-connected area inside and is formed on the ohmic contact layer 13.
  • the active area is rectangular (it can be a rectangle with rounded corners) (it can be a rectangular mesa active area formed by mesa etching, or it can be a rectangular active area formed by ion implantation).
  • the surface shape of the ohmic contact layer 13 is a circular array (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer), and the surface shape of the first metal electrode layer 14 It is also a circular array, formed on the ohmic contact layer 13, and each circle in the circular array is connected.
  • the active area is rectangular (it can be a rectangle with rounded corners) (it can be a rectangular mesa active area formed by mesa etching, or it can be a rectangular active area formed by ion implantation).
  • the surface shape of the ohmic contact layer 13 is a square array (the ohmic contact layer 13 is located in the active area and can be formed in the second epitaxial layer or on the second epitaxial layer); the surface shape of the first metal electrode layer 14 is also It is a square array formed on the ohmic contact layer 13, and each square in the square array of the first metal electrode layer 14 is connected.
  • the window-shaped or array-shaped first metal electrode layer forming electrical contacts can improve the uniformity of the internal electric field distribution of the ultraviolet sensor, thereby helping to achieve better avalanche multiplication performance.

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Abstract

本申请适用于半导体技术领域，提供了一种紫外探测器及其制备方法，该紫外探测器包括：衬底；位于衬底上的第一外延层，该第一外延层为重掺杂外延层；位于第一外延层上的第二外延层，该第二外延层为轻掺杂外延层，或者，该第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；位于第二外延层上或者形成于第二外延层中的欧姆接触层，该欧姆接触层为图形化的重掺杂层；其中，欧姆接触层形成于第二外延层中时，欧姆接触层的上表面不低于第二外延层的上表面，且，欧姆接触层的下表面高于第二外延层的下表面；位于欧姆接触层上的第一金属电极层。本申请能够提高紫外探测器的量子效率。

Description

一种紫外探测器及其制备方法 技术领域
本申请属于半导体技术领域，尤其涉及一种紫外探测器及其制备方法。
 背景技术
近年来，基于半导体的固态紫外探测器研究在国际上受到越来越多的关注，例如，4H-SiC雪崩光电二极管紫外探测器具有高增益、高响应度、低暗电流等优点，能够实现微弱紫外信号甚至紫外单光子的探测。
然而，紫外探测器有背面入射式和正面入射式两种入射方式，其中，背面入射式的紫外探测器由于衬底对光子的吸收，会导致探测器的量子效率大大降低；而传统的正面入射式紫外探测器由于其顶层重掺杂的欧姆接触层的存在，会导致大量短波长的光子被欧姆接触层吸收，从而使得量子效率降低。
 技术问题
有鉴于此，本申请提供了一种紫外探测器及其制备方法，以解决现有技术中的紫外探测器量子效率不高的问题。
 技术解决方案
本申请实施例的第一方面提供了一种紫外探测器，该紫外探测器包括：
衬底；
第一外延层，位于所述衬底上，所述第一外延层为重掺杂外延层；
第二外延层，位于所述第一外延层上，所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；
欧姆接触层，位于所述第二外延层上或者形成于所述第二外延层中，所述欧姆接触层为图形化的重掺杂层；其中，所述欧姆接触层形成于所述第二外延层中时，所述欧姆接触层的上表面不低于所述第二外延层的上表面，且，所述欧姆接触层的下表面高于所述第二外延层的下表面；
第一金属电极层，位于所述欧姆接触层上。
基于第一方面，在第一种可能的实现方式中，所述第一外延层为P型碳化硅外延层，所述第二外延层为N型碳化硅外延层，所述欧姆接触层为N型欧姆接触层；或者，
所述第一外延层为N型碳化硅外延层，所述第二外延层为P型碳化硅外延层，所述欧姆接触层为P型欧姆接触层。
基于第一方面第一种可能的实现方式，在第二种可能的实现方式中，所述第一金属电极层的表面面积不大于所述欧姆接触层的表面面积，且，所述第一金属电极层的表面形状与所述欧姆接触层的表面图形相对应。
基于第一方面第二种可能的实现方式，在第三种可能的实现方式中，所述欧姆接触层的表面图形包括圆环形、方环形、窗口形以及阵列形其中的任意一种。
基于第一方面及第一方面上述任一种可能的实现方式，在第四种可能的实现方式中，所述紫外探测器还包括钝化保护层，所述钝化保护层覆盖于所述第二外延层的外表面上除所述第一金属电极层之外的区域。
基于第一方面第四种可能的实现方式，在第五种可能的实现方式中，所述第二外延层的面积小于所述第一外延层的面积，且，所述第一外延层上的部分区域与所述第二外延层形成一隔离台面，其中，所述部分区域表示所述第一外延层上具有所述第二外延层的区域；
所述紫外探测器还包括第二金属电极层，所述第二金属电极层形成于所述第一外延层上的所述隔离台面之外的区域。
基于第一方面第四种可能的实现方式，在第六种可能的实现方式中，所述衬底为重掺杂衬底；
所述紫外探测器还包括第二金属电极层，所述第二金属电极层位于所述衬底的另一面，该另一面与所述衬底的形成有所述第一外延层的一面相对。
本申请实施例的第二方面提供了一种紫外探测器的制备方法，该制备方法包括：
制备第一半导体外延晶片或者第二半导体外延晶片，其中，所述第一半导体外延晶片由下至上依次包括衬底、第一外延层和第二外延层；所述第二半导体外延晶片由下至上依次包括衬底、第一外延层、第二外延层和第三外延层；其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
对于所述第一半导体外延晶片，在所述第二外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的离子注入窗口，通过所述图形化的离子注入窗口进行离子注入，形成图形化的欧姆接触层；
对于所述第二半导体外延晶片，在所述第三外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的刻蚀窗口，将所述掩膜层上所述刻蚀窗口之外的区域刻蚀至所述第二外延层，形成图形化的欧姆接触层；
去除所述光刻胶和所述掩膜层；
采用台面蚀刻或者离子注入进行隔离，形成有源区；
在所述有源区蒸镀金属并退火，形成第一金属电极层。
基于第二方面，在第一种可能的实现方式中，所述在所述有源区蒸镀金属并退火，形成第一金属电极层之后还包括：
在所述第一半导体外延晶片或者所述第二半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
基于第二方面及第二方面第一种可能的实现方式，在第二种可能的实现方式中，所述第一外延层为P型碳化硅外延层，所述第二外延层为N型碳化硅外延层，所述欧姆接触层为N型欧姆接触层；或者，
所述第一外延层为N型碳化硅外延层，所述第二外延层为P型碳化硅外延层，所述欧姆接触层为P型欧姆接触层。
 有益效果
本申请与现有技术相比存在的有益效果是，本申请提供的紫外探测器包括由第一外延层、第二外延层和图形化的欧姆接触层构成的探测器外延结构，其中，第二外延层为紫外探测器的吸收倍增区，在采用正面入射时，图形化的欧姆接触层对入射光子的吸收大大减少，尤其是可以减少欧姆接触层对短波长光子的吸收。因此，到达吸收倍增区的入射光子量会大大增加，从而达到了提高紫外探测器的量子效率的目的。
 附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的现有技术中欧姆接触层在一种紫外探测器中的结构的示意图；
图2是本申请实施例提供的一种紫外探测器的结构示意图；
图3是本申请实施例提供的另一种紫外探测器的结构示意图；
图4是本申请实施例提供的又一种紫外探测器的结构示意图；
图5是本申请实施例提供的再一种紫外探测器的结构示意图；
图6是本申请实施例提供的紫外探测器的一种有源区表面的示意图；
图7是本申请实施例提供的紫外探测器的第二种有源区表面的示意图；
图8是本申请实施例提供的紫外探测器的第三种有源区表面的示意图；
图9是本申请实施例提供的紫外探测器的第四种有源区表面的示意图；
图10是本申请实施例提供的紫外探测器的第五种有源区表面的示意图；
图11是本申请实施例提供的紫外探测器的第六种有源区表面的示意图。
 本发明的实施方式
以下描述中，为了说明而不是为了限定，提出了诸如特定系统结构、技术之类的具体细节，以便透彻理解本申请实施例。然而，本领域的技术人员应当清楚，在没有这些具体细节的其它实施例中也可以实现本申请。在其它情况中，省略对众所周知的系统、装置、电路以及方法的详细说明，以免不必要的细节妨碍本申请的描述。
为使本申请的目的、技术方案和优点更加清楚，下面将结合附图通过具体实施例来进行说明。
首先说明现有技术中，欧姆接触层在一种紫外探测器中的结构设计，参见图1（剖面图），其提供的紫外探测器由下至上包括：衬底10、第一外延层11、第二外延层12和欧姆接触层13。可以看出，欧姆接触层13完全覆盖于第二外延层12的上方，采用正面入射方式（从上方向下入射）时，欧姆接触层13会吸收入射的光子，减少了到达第二外延层12（吸收倍增区）的光子数量，从而会造成紫外探测器的量子效率降低。
本申请实施例提供的紫外探测器，其欧姆接触层为图形化结构，图形化结构的欧姆接触层对其下方的第二外延层的遮挡减少，从而可以降低欧姆接触层对入射光子的吸收量，提高量子效率。
参见图2，是本申请实施例提供的一种紫外探测器的结构示意图（剖面图），其欧姆接触层形成于第二外延层中，如图2所示，其提供的紫外探测器包括：衬底10、第一外延层11、第二外延层12、形成于第二外延层12中的欧姆接触层13和位于欧姆接触层13上的第一金属电极层14。在该实施例中，欧姆接触层13的表面形状为圆环状。
在本申请实施例中，衬底可以为硅、蓝宝石、氮化镓或碳化硅等材料中的任意一种。
在本申请实施例中，欧姆接触层13的上表面可以与第二外延层12的上表面持平。在实际应用中，欧姆接触层13形成于第二外延层12中，欧姆接触层13的上表面可以不低于第二外延层12的上表面，且，欧姆接触层13的下表面需高于第二外延层12的下表面。具体以第一外延层11、第二外延层12和欧姆接触层13能够共同形成探测器外延结构为准，其中，第一外延层11为重掺杂外延层；第二外延层12为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；欧姆接触层13为图形化的重掺杂层，该紫外探测器采用正面入射的方式，第二外延层12可以整层为轻掺杂外延层，即为紫外探测器的吸收倍增区；第二外延层12也可以为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构，也即吸收层和倍增层分离的结构。
在本申请实施例中，第一金属电极层14欧姆接触层13上，其表面面积不大于欧姆接触层13的表面面积。
在本申请实施例中，欧姆接触层13的掺杂浓度可以在1×10 18cm -3~1×10 20cm -3之间，深度可以在0.01～0.5μm之间。第一外延层11的掺杂浓度可以在1×10 18cm -3~1×10 20cm -3之间，厚度可以在1～3μm之间。第二外延层12如果为轻掺杂的单一外延层，其掺杂浓度可以在1×10 15cm -3~1×10 17cm -3之间；第二外延层12如果为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构，其轻掺杂外延层浓度可以在1×10 15cm -3~1×10 17cm -3之间，重掺杂浓度可以在5×10 17cm -3~1×10 20cm -3之间；第二外延层12的总厚度可以在0.1～50μm之间。。
在本申请实施例中，紫外探测器还可以包括钝化保护层，以抑制紫外探测器的表面漏电，减小暗电流。如图2所示，钝化保护层15可以覆盖于第二外延层12的外表面上除第一金属电极层14之外的区域。钝化保护层可以为SiO 2、Al 2O 3、HfO 2、Y 2O 3、SiN x材料中的一种或任意几种组合，厚度可以在50nm~10μm之间。
在本申请实施例中，如图2所示，第二外延层12的面积可以小于第一外延层11的面积，且，第一外延层11上的部分区域与第二外延层12形成一隔离台面（隔离台面上的上表面即为紫外探测器的有源区，欧姆接触层13位于有源区内），第一外延层11上的部分区域指第一外延层11上形成有第二外延层12的区域。
在本申请实施例中，隔离台面可以是倾角为90度的垂直结构，也可以是具有非垂直倾角的台面结构。
在本申请实施例中，如图2所示，紫外探测器还包括第二金属电极层16，第二金属电极层16形成于第一外延层11上的所述隔离台面之外的区域，例如可以在隔离台面之外环绕分布。
可选的，在本申请实施例中，第二金属电极层16还可以位于衬底10的另一面，该另一面与衬底10的形成有第一外延层11的一面相对，也即第一外延层11可以位于衬底10上方的一面，第二金属电极层16可以位于衬底10下方的一面。该实施方式中，衬底需要采用重掺杂衬底。
在本申请实施例中，第一外延层可以为P型碳化硅外延层，第二外延层可以为N型碳化硅外延层，欧姆接触层可以为N型欧姆接触层，此实施例下，第一金属电极层即为阴极金属电极层，其可以与N型欧姆接触层形成电连接；第二金属电极层即为阳极金属电极层，其可以与第一外延层（P型碳化硅外延层）形成电连接，第一外延层、第二外延层和欧姆接触层形成探测器外延结构。
在本申请实施例中，第一外延层可以为N型碳化硅外延层，第二外延层可以为P型碳化硅外延层，欧姆接触层可以为P型欧姆接触层，此实施例下，第一金属电极层即为阳极金属电极层，其可以与P型欧姆接触层形成电连接；第二金属电极层即为阴极金属电极层，其可以与第一外延层（N型碳化硅外延层）形成电连接，第一外延层、第二外延层和欧姆接触层形成探测器外延结构。
本申请实施例中，P型和N型分别用于表示不同的半导体材料，P型表示空穴型半导体，N型表示电子型半导体。
图2所示实施例的紫外探测器可以采用以下制备方法得到：
制备第一半导体外延晶片，其中，所述第一半导体外延晶片由下至上依次包括衬底、第一外延层和第二外延层，其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
在第一半导体外延晶片的第二外延层表面制备掩膜层，在掩膜层涂覆光刻胶并进行光刻，形成图形化的离子注入窗口，通过图形化的离子注入窗口进行离子注入，形成图形化的欧姆接触层；
去除光刻胶和掩膜层；
采用台面蚀刻进行隔离，形成有源区；
在有源区蒸镀金属并退火，形成第一金属电极层。
在本申请实施例中，上述制备方法还可以包括制备钝化保护层的步骤：在所述有源区蒸镀金属并退火，形成第一金属电极层之后，在所述第一半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
由上可知，本申请提供的紫外探测器包括由第一外延层、第二外延层和图形化的欧姆接触层构成的探测器外延结构，其中，第二外延层为紫外探测器的吸收倍增区，在采用正面入射时，图形化的欧姆接触层对入射光子的吸收大大减少，尤其是可以减少欧姆接触层对短波长光子的吸收。因此，到达吸收倍增区的入射光子量会大大增加，从而达到了提高紫外探测器的量子效率的目的。
参见图3，是本申请实施例提供的另一种紫外探测器的结构示意图（剖面图），与图2所示实施例不同的是，图3所示实施例中紫外探测器的欧姆接触层13位于第二外延层12上，图3所示实施例中紫外探测器可以采用以下制备方法得到：
制备第二半导体外延晶片，其中，所述第二半导体外延晶片由下至上依次包括衬底、第一外延层、第二外延层和第三外延层；其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
在所述第三外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的刻蚀窗口，将所述掩膜层上所述刻蚀窗口之外的区域刻蚀至所述第二外延层，形成图形化的欧姆接触层；
去除所述光刻胶和所述掩膜层；
采用台面蚀刻进行隔离，形成有源区；
在所述有源区蒸镀金属并退火，形成第一金属电极层。
在本申请实施例中，该制备方法还可以包括制备钝化保护层的步骤：在所述有源区蒸镀金属并退火，形成第一金属电极层之后，在所述第二半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
图2及图3所示实施例提供的紫外探测器采用了台面隔离的方式，其有源区即为紫外探测器的隔离台面。参见图4，是本申请实施例提供的又一种紫外探测器的结构示意图（剖面图），与图2及图3所示实施例相比，图4所示实施例中的紫外探测器采用离子注入的方式实现有源区的隔离，而无需制作隔离台面。其欧姆接触层形成于第二外延层中（参考图2所示实施例，在此不再赘述）。另外，在该实施方式中，衬底10可以采用重掺杂衬底，第二金属电极层16可以位于衬底10的另一面，该另一面与衬底10的形成有第一外延层11的一面相对；也即，第一外延层11可以位于衬底10上方的一面，第二金属电极层16可以位于衬底10下方的一面。其制备方法如下：
制备第一半导体外延晶片，其中，所述第一半导体外延晶片由下至上依次包括衬底、第一外延层和第二外延层，其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
在第一半导体外延晶片的第二外延层表面制备掩膜层，在掩膜层涂覆光刻胶并进行光刻，形成图形化的离子注入窗口，通过图形化的离子注入窗口进行离子注入，形成图形化的欧姆接触层；
去除光刻胶和掩膜层；
采用离子注入进行隔离，形成有源区；
在有源区蒸镀金属并退火，形成第一金属电极层。
该制备方法还可以包括制备钝化保护层的步骤：在所述有源区蒸镀金属并退火，形成第一金属电极层之后，在所述第一半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
该制备方法还可以包括制备第二金属电极层的步骤：在衬底的另一面蒸镀金属并退火，形成第二金属电极层，该另一面与衬底上形成有第一外延层的一面相对。
参见图5，为本申请实施例提供的再一种紫外探测器的结构示意图，其与图4所示实施例均采用离子注入的方式进行有源区的隔离，无需制作隔离台面。其欧姆接触层位于第二外延层上（参考图2所示实施例，在此不再赘述）。另外，在该实施方式中，衬底10可以采用重掺杂衬底，第二金属电极层16可以位于衬底10的另一面，该另一面与衬底10的形成有第一外延层11的一面相对；也即，第一外延层11可以位于衬底10上方的一面，第二金属电极层16可以位于衬底10下方的一面。其制备方法如下：
制备第二半导体外延晶片，其中，所述第二半导体外延晶片由下至上依次包括衬底、第一外延层、第二外延层和第三外延层；其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
在所述第三外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的刻蚀窗口，将所述掩膜层上所述刻蚀窗口之外的区域刻蚀至所述第二外延层，形成图形化的欧姆接触层；
去除所述光刻胶和所述掩膜层；
采用离子注入进行隔离，形成有源区；
在所述有源区蒸镀金属并退火，形成第一金属电极层。
在本申请实施例中，该制备方法还可以包括制备钝化保护层的步骤：在所述有源区蒸镀金属并退火，形成第一金属电极层之后，在所述第二半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
该制备方法还可以包括制备第二金属电极层的步骤：在衬底的另一面蒸镀金属并退火，形成第二金属电极层，该另一面与衬底上形成有第一外延层的一面相对。
在上述实施例中，欧姆接触层13的表面图形可以为圆环形、方环形、窗口形或者阵列形，欧姆接触层13的表面图形还可以为其它形状，只要其具备可以让入射光子直接穿过的图形化的间隙即可。
在上述实施例中，第一金属电极层14的表面形状可以与欧姆接触层13的表面图形相对应，例如，欧姆接触层13的表面图形为圆环形时，第一金属电极层14的表面形状也可以相应的为圆环形。
参见图6-图11，为分别示出了紫外探测器的有源区表面的六种图形的示意图（俯视图）。
如图6所示，其有源区为圆形（可以为采用台面刻蚀形成的圆形台面有源区，或者可以为采用离子注入方式形成的圆形有源区），其欧姆接触层13的表面形状为圆环形（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上），第一金属电极层14的表面形状也为圆环形，形成于欧姆接触层13上。
如图7所示，其有源区为矩形（可以为圆角矩形）（可以为采用台面刻蚀形成的矩形台面有源区，或者可以为采用离子注入方式形成的矩形有源区），其欧姆接触层13的表面形状为矩形的环形（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上），第一金属电极层14的表面形状也为矩形的环形，形成于欧姆接触层13上。
如图8所示，其有源区为圆形（可以为采用台面刻蚀形成的圆形台面有源区，或者可以为采用离子注入方式形成的圆形有源区），其欧姆接触层13的表面形状为圆窗形（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上），第一金属电极层14的表面形状为内部具有十字连通区域的圆窗形，形成于欧姆接触层13上。
如图9所示，其有源区为矩形（可以为圆角矩形）（可以为采用台面刻蚀形成的矩形台面有源区，或者可以为采用离子注入方式形成的矩形有源区），其欧姆接触层13的表面形状为矩形窗口形（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上），第一金属电极层14的表面形状也为内部具有十字连通区域的矩形窗口形，形成于欧姆接触层13上。
如图10所示，其有源区为矩形（可以为圆角矩形）（可以为采用台面刻蚀形成的矩形台面有源区，或者可以为采用离子注入方式形成的矩形有源区），其欧姆接触层13的表面形状为圆形阵列（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上），第一金属电极层14的表面形状也为圆形阵列，形成于欧姆接触层13上，且，圆形阵列中的各个圆形连通。
如图10所示，其有源区为矩形（可以为圆角矩形）（可以为采用台面刻蚀形成的矩形台面有源区，或者可以为采用离子注入方式形成的矩形有源区），其欧姆接触层13的表面形状为方形阵列（欧姆接触层13位于有源区内，可以形成于第二外延层中，也可以位于第二外延层上）；第一金属电极层14的表面形状也为方形阵列，形成于欧姆接触层13上，且，第一金属电极层14的方形阵列中的各个方形连通。
在本申请实施例中，窗口状或阵列状的形成电接触的第一金属电极层能够改善紫外传感器的内部电场分布的均匀性，从而有利于实现更好的雪崩倍增性能。
以上所述实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种紫外探测器，其特征在于，所述紫外探测器包括：
    衬底；
    第一外延层，位于所述衬底上，所述第一外延层为重掺杂外延层；
    第二外延层，位于所述第一外延层上，所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；
    欧姆接触层，位于所述第二外延层上或者形成于所述第二外延层中，所述欧姆接触层为图形化的重掺杂层；其中，所述欧姆接触层形成于所述第二外延层中时，所述欧姆接触层的上表面不低于所述第二外延层的上表面，且，所述欧姆接触层的下表面高于所述第二外延层的下表面；
    第一金属电极层，位于所述欧姆接触层上。
  2. 根据权利要求1所述的紫外探测器，其特征在于，所述第一外延层为P型碳化硅外延层，所述第二外延层为N型碳化硅外延层，所述欧姆接触层为N型欧姆接触层；或者，
    所述第一外延层为N型碳化硅外延层，所述第二外延层为P型碳化硅外延层，所述欧姆接触层为P型欧姆接触层。
  3. 根据权利要求2所述的紫外探测器，其特征在于，所述第一金属电极层的表面面积不大于所述欧姆接触层的表面面积，且，所述第一金属电极层的表面形状与所述欧姆接触层的表面图形相对应。
  4. 根据权利要求3所述的紫外探测器，其特征在于，所述欧姆接触层的表面图形包括圆环形、方环形、窗口形以及阵列形其中的任意一种。
  5. 根据权利要求1至4任一项所述的紫外探测器，其特征在于，所述紫外探测器还包括钝化保护层，所述钝化保护层覆盖于所述第二外延层的外表面上除所述第一金属电极层之外的区域。
  6. 根据权利要求5所述的紫外探测器，其特征在于，所述第二外延层的面积小于所述第一外延层的面积，且，所述第一外延层上的部分区域与所述第二外延层形成一隔离台面，其中，所述部分区域表示所述第一外延层上具有所述第二外延层的区域；
    所述紫外探测器还包括第二金属电极层，所述第二金属电极层形成于所述第一外延层上的所述隔离台面之外的区域。
  7. 根据权利要求5所述的紫外探测器，其特征在于，所述衬底为重掺杂衬底；
    所述紫外探测器还包括第二金属电极层，所述第二金属电极层位于所述衬底的另一面，该另一面与所述衬底的形成有所述第一外延层的一面相对。
  8. 一种紫外探测器的制备方法，其特征在于，所述制备方法包括：
    制备第一半导体外延晶片或者第二半导体外延晶片，其中，所述第一半导体外延晶片由下至上依次包括衬底、第一外延层和第二外延层；所述第二半导体外延晶片由下至上依次包括衬底、第一外延层、第二外延层和第三外延层；其中，所述第一外延层为重掺杂外延层；所述第二外延层为轻掺杂外延层，或者，所述第二外延层为由至少一层轻掺杂外延层和至少一层重掺杂外延层构成的双层或多层结构；所述第三外延层为重掺杂外延层；
    对于所述第一半导体外延晶片，在所述第二外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的离子注入窗口，通过所述图形化的离子注入窗口进行离子注入，形成图形化的欧姆接触层；
    对于所述第二半导体外延晶片，在所述第三外延层表面制备掩膜层，在所述掩膜层涂覆光刻胶并进行光刻，形成图形化的刻蚀窗口，将所述掩膜层上所述刻蚀窗口之外的区域刻蚀至所述第二外延层，形成图形化的欧姆接触层；
    去除所述光刻胶和所述掩膜层；
    采用台面蚀刻或者离子注入进行隔离，形成有源区；
    在所述有源区蒸镀金属并退火，形成第一金属电极层。
  9. 根据权利要求8所述的紫外探测器的制备方法，其特征在于，所述在所述有源区蒸镀金属并退火，形成第一金属电极层之后还包括：
    在所述第一半导体外延晶片或者所述第二半导体外延晶片表面沉积钝化保护层，并刻蚀出电极窗口。
  10. 根据权利要求8或9所述的紫外探测器的制备方法，其特征在于，所述第一外延层为P型碳化硅外延层，所述第二外延层为N型碳化硅外延层，所述欧姆接触层为N型欧姆接触层；或者，
    所述第一外延层为N型碳化硅外延层，所述第二外延层为P型碳化硅外延层，所述欧姆接触层为P型欧姆接触层。
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