CN114400235B - Back-illuminated light detection array structure and preparation method thereof - Google Patents

Back-illuminated light detection array structure and preparation method thereof Download PDF

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CN114400235B
CN114400235B CN202210045713.4A CN202210045713A CN114400235B CN 114400235 B CN114400235 B CN 114400235B CN 202210045713 A CN202210045713 A CN 202210045713A CN 114400235 B CN114400235 B CN 114400235B
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light
photodiode
mesa
filling material
array
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CN114400235A (en
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石彬
祁帆
蔡鹏飞
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NANO (BEIJING) PHOTONICS Inc
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14618—Containers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H01L27/14629—Reflectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1463—Pixel isolation structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14634—Assemblies, i.e. Hybrid structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14636—Interconnect structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
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    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/1469—Assemblies, i.e. hybrid integration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The invention provides a back irradiation light detection array structure, which comprises: light focusing structure, substrate, light collecting structure, photodiode, and filler. The invention also provides a preparation method of the back irradiation light detection array structure. The invention provides a novel design of a photoelectric tube array, and simultaneously integrates a light focusing structure and a light collecting structure, so that the external quantum efficiency of a sensor system based on a small-size photodiode array can be effectively improved, and the overall light receiving efficiency is greatly improved; for the application scene of high-speed optical communication, only 1 or 4-8 photoelectric detectors are needed, and the structural design of the invention can reduce capacitance and dark current as well, and simultaneously ensures higher responsivity and larger alignment tolerance when being coupled with optical fibers.

Description

Back-illuminated light detection array structure and preparation method thereof
Technical Field
The invention belongs to the technical field of photoelectric detectors, and particularly relates to a back irradiation light detection array structure and a preparation method thereof.
Background
High density photodiode arrays have a number of applications in the sensor field, and in order to increase the sensitivity of such array sensors, it is often necessary to make the size of the photodiodes very small, such as a few microns. While this design is effective in reducing dark current and capacitance of the chip, it requires a complex optical design to ensure that the signal beam can be efficiently collected and directed onto the photodiodes, the complexity of this design being particularly apparent for arrays having tens of thousands of photodiodes. Patent document 201980001248.0 discloses a germanium-based focal plane array for a short infrared spectral range, comprising: pyramid shaped silicon-based and germanium photodiodes. The technical problems are that the devices in the structure are limited too much, so that the application scene is limited, the preparation difficulty is high, for example, silicon is required to be pyramid, and for example, the photodiode is prepared in pyramid silicon, so that the photodiode can be PN or PIN type, and the like, and the silicon is required to be prepared first, and then the photodiode is prepared, so that the manufacturing difficulty is increased. In addition, the light detection structure in the prior art has the technical problems of poor collection effect and poor practicability.
Disclosure of Invention
In order to solve the technical problems, the invention provides a back-illuminated light detection array structure and a preparation method thereof. The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview and is intended to neither identify key/critical elements nor delineate the scope of such embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
The invention adopts the following technical scheme:
In some alternative embodiments, there is provided a back-illuminated photo-detection array structure comprising: the incident light is reflected for a plurality of times in the light collecting structure and then is emitted out through the tail end surface of the light collecting structure; the light focusing structure is positioned at the head end face of the light collecting structure and is used for focusing external signal light into the light collecting structure; and the photodiode is positioned on the surface of the tail end surface of the light collecting structure and used for absorbing the light emitted by the light collecting structure, and the photodiode is a germanium-silicon photodiode or a germanium-silicon avalanche photodiode.
Further, the back-illuminated light detection array structure further includes: a substrate, the light collecting structure is positioned on the top surface of the substrate, and the light focusing structure is positioned on the back surface of the substrate; the light collection structure includes: at least one mesa whose inner wall reflects incident light multiple times and whose outgoing light is absorbed by the photodiode arranged on the tail end surface of the mesa; the light focusing structure includes: at least one microlens corresponding to the mesa, which focuses external signal light to an inside of the mesa corresponding thereto.
Further, the back-illuminated light detection array structure further includes: a filling material filled between the mesas; the filling material is polymer filling material or SiO2 filling material, the SiO2 filling material is ground by using a CMP process, and the polymer filling material is filled in a glue homogenizing mode.
Further, the external structure of the table top is one or more of a polygonal pyramid, a truncated cone, a polygonal column and a cylinder; when the external structure is in the shape of a polygonal pyramid or a polygonal column, the bottom surface of the table top can be in the shape of a regular polygon or an irregular polygon; when the external structure is round table or cylinder, the bottom surface of the table top is round or elliptical.
Further, the outer wall of the table top is plated with a dielectric layer, and the refractive index of the dielectric layer is smaller than that of the filling material.
Further, the dielectric layer is a metal film, and the metal film forms a reflecting mirror surface on the outer wall of the table top.
Further, the mesa is formed separately from SiO2, siN or polymeric material and is placed on top of the photodiode using glue or encapsulation.
Further, the micro lens is a convex lens, and the micro lens is prepared on the substrate, or is singly prepared by using SiO2, siN or polymer materials and then is adhered or bonded on the substrate.
In some optional embodiments, the present invention further provides a method for preparing a back-illuminated light detection array structure, including: preparing a photodiode array on a silicon wafer; a light collection structure is fabricated on top of the photodiode array.
Further, the preparation method of the back irradiation light detection array structure further comprises the following steps: preparing a dielectric layer on the outer wall of the mesa of the light collection structure; filling up the space between the mesas with a filling material; preparing electrodes and metal connecting wires of the photodiode and metal end faces for bonding; and preparing a micro lens array on the back surface of the silicon wafer.
The invention has the beneficial effects that: the invention provides a novel design of a photoelectric tube array, and simultaneously integrates a light focusing structure and a light collecting structure, so that the external quantum efficiency of a sensor system based on a small-size photodiode array can be effectively improved, and the overall light receiving efficiency is greatly improved; for the application scene of high-speed optical communication, only one or 4-8 photoelectric detectors are needed, and the structural design of the invention can reduce capacitance and dark current as well, and simultaneously ensures higher responsivity and larger alignment tolerance when being coupled with optical fibers.
Drawings
FIG. 1 is a schematic diagram of a back-illuminated photodetector array configuration according to the present invention;
FIG. 2 is a schematic top view of a back-illuminated photodetector array configuration according to the present invention;
FIG. 3 is a schematic illustration of a first exemplary light focusing situation for a microlens of the present invention;
FIG. 4 is a schematic diagram of a second exemplary light focusing scenario of the microlens of the present invention;
FIG. 5 is a schematic diagram of a third exemplary light focusing scenario for a microlens of the present invention;
FIG. 6 is a schematic view of the structure of the polygonal pyramid mesa of the present invention;
FIG. 7 is a schematic view of the structure of a polygon prism mesa of the present invention;
FIG. 8 is a schematic view of the structure of a cylindrical mesa of the present invention;
FIG. 9 is a schematic view of the structure of the truncated cone mesa of the present invention;
FIG. 10 is a schematic view of one of the light reflections inside the mesa of the present invention;
FIG. 11 is a schematic view of another light reflection inside the mesa of the present invention;
FIG. 12 is a schematic view of one of the light reflections inside a mesa having a dielectric layer in accordance with the present invention;
FIG. 13 is another schematic view of light reflection inside a mesa having a dielectric layer in accordance with the present invention;
fig. 14 is a schematic flow chart of a method for manufacturing a back-illuminated photo-detection array structure according to the present invention.
Detailed Description
The following description and the drawings sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may involve structural, logical, electrical, process, and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in, or substituted for, those of others.
In some illustrative embodiments, as shown in FIGS. 1-2, the present invention provides a back-illuminated photo-detection array structure comprising: a light focusing structure, a substrate 2, a light collecting structure, a photodiode 1, a filling substance 3.
The light focusing structure is used for focusing external signal light into the light collecting structure, and specifically, the light focusing structure comprises: at least one microlens 4, the microlens 4 serves to focus incident light, and a plurality of microlenses 4 are arranged to form an array. The light focusing structure is positioned on the back of the substrate 2, namely, the micro lens 4 is attached to the back of the substrate 2, and the micro lens 4 focuses the external signal light into the light collecting structure.
Wherein the micro-lens 4 is a convex lens, so that light outside the substrate 2 can be effectively focused inside the substrate 2, three typical light focusing situations of the micro-lens 4 are shown in fig. 3-5. The microlenses 4 are produced directly on the substrate 2 or are separately produced using SiO 2, siN or a polymeric material and then glued or bonded to the substrate 2.
The surface of the microlens 4 may be covered with an anti-reflection layer to enhance the light projection efficiency.
Preferably, the thickness of the substrate 2 is 50 micrometers to 750 micrometers, and the present invention designs the thickness value within this range to enhance the light collection efficiency.
The light collecting structure is used for collecting incident light, and the incident light is reflected for multiple times in the light collecting structure and then is emitted out through the tail end face of the light collecting structure. The light focusing structure is positioned at the head end face of the light collecting structure. Specifically, the light collection structure includes: at least one mesa 5, a plurality of mesas 5 are arranged to form an array. The mesas 5 are in one-to-one correspondence with the microlenses 4, i.e., each microlens 4 focuses the external signal light into the mesa 5 above it.
The light collecting structure is located on the top surface of the substrate 2, that is, the bottom of the mesa 5 is in contact with the substrate 2, the inner wall of the mesa 5 reflects the incident light multiple times to form emergent light, and the emergent light is emitted from the top of the mesa 5 and absorbed by the photodiode 1 disposed on the top of the mesa 5, where the top of the mesa 5 may also be referred to as the tail end surface of the mesa 5, and the tail end surface of the mesa 5 is referred to as the tail end surface of the light collecting structure.
The mesa array may be prepared directly on the substrate 2. The external structure of the table top 5 is one or more of a polygonal pyramid, a truncated cone, a polygonal column and a cylinder. The polygonal pyramid mesa 5 has a structural shape as shown in fig. 6, and may be a triangular pyramid, a dodecagon pyramid, or the like. The structural shape of the polygon prism mesa 5 is shown in fig. 7. The structural shape of the cylindrical mesa 5 is shown in fig. 8. The structural shape of the truncated cone table top 5 is shown in fig. 9.
When the external structure shape of the mesa 5 is a polygonal pyramid or a polygonal column, the bottom surface shape of the mesa 5 may be a regular polygon or an irregular polygon; when the external structure of the table top 5 is round table or cylindrical, the bottom surface of the table top 5 is round or elliptical. Therefore, the table top 5 of the invention can be in various forms, but is not limited to one of the forms, thereby improving the practicability of the structure, being applicable to more application scenes and reducing the preparation difficulty.
The mesa 5 may be prepared by dry or wet etching. Mesa 5 is prepared separately using SiO 2, siN or a polymeric material and glued on top of photodiode 1, or the prepared mesa 5 is placed on top of photodiode 1 using encapsulation.
The photodiode 1 is used for absorbing light emitted by the light collecting structure and is positioned on the surface of the tail end face of the light collecting structure, namely, is connected with the top surface of the table top 5. The photodiode 1 is a germanium-silicon photodiode or a germanium-silicon avalanche photodiode, so that the types of the photodiode are more various, and the photodiode is suitable for different application scenes. Each photodiode is provided with a P electrode and an N electrode, and the same electrodes are connected through metal wires.
The photodiode 1 uses silicon as a substrate, a layer of N-doped silicon as a bottom connection layer, a layer of P-doped silicon as a top connection layer, and germanium as an absorption layer. For an avalanche photodiode, the following features are provided: using a layer of intrinsic silicon as a photomultiplier layer; a layer of P-doped silicon is used as the charge layer.
The photodiode 1 is prepared on the top of the table top 5 and can be a PN type photodiode or a PIN type photodiode or an avalanche type photodiode, so that the preparation method can prepare the photodiode 1 firstly and then prepare the light collecting structure, and the preparation of the photodiode 1 in the table top 5 is not needed, so that the preparation difficulty is greatly reduced.
The invention uses the light focusing structure to focus the external signal light into the range of the light collecting structure, then uses the light collecting structure to make the light reflect on the inner side wall for multiple times, finally transmits the light to the tail end of the light collecting structure, and the tail end of the light collecting structure is directly provided with the photodiode 1, the photodiode 1 absorbs the transmitted light, the invention has better detection effect in the photodiode array applied in the low-speed sensor field and the high-speed optical communication field.
The filling material 3 fills between the mesas 5. The invention fills the gaps between the table tops 5 completely by using the filling material 3 to planarize the front surface of the chip, not only electrically isolates each single photodiode in the photodiode array, but also improves the structural strength and the surface flatness.
The filling material 3 is a polymer filling material or a SiO 2 filling material, the SiO 2 filling material is ground by using a CMP process, and the polymer filling material is filled in a spin-coating mode, so that the preparation flexibility is improved. Spin coating is one of the basic steps of the photolithography process, and is also called spin coating or spin coating, and after the film forming treatment, the silicon wafer is coated with a liquid phase photoresist material immediately by a spin coating method.
The side wall of the mesa 5 may be in direct contact with the filling material 3, or may be in contact with the filling material 3 after the dielectric layer 6 is plated on the outer wall of the mesa 5. When the filling material 3 is in direct contact with the mesa 5, reflection of light inside the mesa 5 is achieved by utilizing the difference in refractive index, thereby improving the overall collection efficiency of light. The refractive index of the dielectric layer 6 is smaller than that of the filling material 3, so that the total reflection angle of the mesa 5 when the mesa is emitted from inside to outside is increased.
The dielectric layer 6 is a metal film that forms a mirror surface on the outer wall of the mesa so that any angle of light exiting from the interior of the mesa at the sidewalls can be reflected. The selected metal should have very low absorption in the band in which the device operates, such as in the 1200-1600 nm band, and aluminum metal is particularly selected.
As shown in fig. 10-13, the light forms multiple reflections at the sidewalls of mesa 5 for the light concentrated by microlens 4, and is eventually absorbed by photodiode 1 on mesa 5. According to the invention, the outer wall of the table top 5 is covered with a dielectric layer 6 with different refractive indexes from the table top or a metal film, and then the dielectric layer is filled with a filling material 3, so that the light collection effect is greatly improved.
When the photodiode 1, the microlens 4, and the mesa 5 are one, a single diode chip is formed. The photodiode 1, the microlens 4, and the mesa 5 may also be prepared as an array structure.
In some illustrative embodiments, as shown in fig. 1,2, and 14, the present invention provides a method for manufacturing a back-illuminated light detection array structure, including the steps of:
101: the photodiode array is fabricated on a silicon wafer, which is the substrate 2.
102: A light collection structure is fabricated on top of the photodiode array. The light collection structure includes: mesa 5, the mesa array may be prepared directly on substrate 2, mesa 5 may be prepared by dry or wet etching. Mesa 5 is prepared separately using SiO 2, siN or a polymeric material and glued on top of photodiode 1, or the prepared mesa 5 is placed on top of photodiode 1 using encapsulation.
The preparation method of the invention prepares the photodiode 1 firstly and then prepares the light collecting structure, and does not need to prepare the photodiode in the mesa 5, thereby greatly reducing the preparation difficulty.
103: A reflective layer, i.e. a dielectric layer, is prepared on the outer wall of the mesa 5, this step being an optional step. The refractive index of the dielectric layer is smaller than that of the filling material 3, so that the total reflection angle of the mesa 5 when the mesa is emitted from inside to outside is increased.
104: The space between the mesas 5 is filled with a filling substance 3. The filler material 3 not only electrically isolates each individual photodiode in the photodiode array, but also improves structural strength and surface planarity.
The filling material 3 is a polymer filling material or a SiO 2 filling material, the SiO 2 filling material is ground by using a CMP process, and the polymer filling material is filled in a spin-coating mode, so that the preparation flexibility is improved. Spin coating is one of the basic steps of the photolithography process, and is also called spin coating or spin coating, and after the film forming treatment, the silicon wafer is coated with a liquid phase photoresist material immediately by a spin coating method.
105: Electrodes and metal connection tracks of the photodiode 1 and metal end faces for bonding are prepared. The metal end face can be prepared into a copper column, so that the application scene of chip flip-chip packaging is convenient.
106: A microlens array is fabricated on the back side of the silicon wafer. The microlens array is directly prepared on the substrate 2 or is separately prepared using SiO2, siN or a polymer material and then adhered or bonded to the substrate 2.
107: The silicon wafer is diced to form chips.
The method has the advantages of simple flow, low preparation difficulty, high light collection efficiency, capacity reduction, dark current reduction, high responsivity and high alignment tolerance when coupled with the optical fiber, and can ensure the prepared photoelectric tube array.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

Claims (5)

1. A back-illuminated photo-detection array structure for enhancing the external quantum efficiency of a sensor system based on a small-sized photodiode array;
Comprising the following steps:
The incident light is reflected for a plurality of times in the light collecting structure and then is emitted out through the tail end surface of the light collecting structure; the light collection structure includes: at least one mesa whose inner wall reflects incident light multiple times and whose outgoing light is absorbed by the photodiode arranged on the tail end surface of the mesa;
The light focusing structure is positioned at the head end face of the light collecting structure and is used for focusing external signal light into the light collecting structure; the light focusing structure includes: at least one microlens corresponding to the mesa, the microlens focusing external signal light to an inside of the mesa corresponding thereto;
A filling material filled between the mesas; the filling material is polymer filling material or SiO 2 filling material, the SiO 2 filling material is ground by using a CMP process, and the polymer filling material is filled in a glue homogenizing mode;
The photodiode is positioned on the surface of the tail end face of the light collecting structure and used for absorbing light emitted by the light collecting structure, and the photodiode is a germanium-silicon photodiode or a germanium-silicon avalanche photodiode;
a substrate, the light collecting structure is positioned on the top surface of the substrate, and the light focusing structure is positioned on the back surface of the substrate;
the preparation method comprises the following steps:
The first step: preparing a photodiode array on a silicon wafer; wherein, the photodiode is not required to be prepared in the mesa;
And a second step of: preparing a light collection structure on top of the photodiode array; the mesa is singly prepared by using SiO 2, siN or polymer materials and is adhered to the top of the photodiode by using glue;
and a third step of: preparing a dielectric layer on the outer wall of the mesa of the light collection structure;
fourth step: filling up the space between the mesas with a filling material;
Fifth step: preparing electrodes and metal connecting wires of the photodiode and metal end faces for bonding;
Sixth step: and preparing a micro lens array on the back surface of the silicon wafer.
2. The back-illuminated photodetector array structure according to claim 1, wherein the mesa has an external structure shape of one of a polygonal pyramid, a truncated cone, a polygonal column, and a cylinder; when the external structure is in the shape of a polygonal pyramid or a polygonal column, the bottom surface of the table top is in the shape of a regular polygon or an irregular polygon; when the external structure is round table or cylinder, the bottom surface of the table top is round or elliptical.
3. The back-illuminated photodetector array structure as in claim 2, wherein said dielectric layer has a refractive index less than a refractive index of said filler material.
4. A back-illuminated photodetector array structure as in claim 3, wherein said dielectric layer is a metal film forming a mirror surface on the outer wall of said mesa.
5. The back-illuminated photodetector array structure according to claim 4, wherein said microlenses are convex lenses and said microlenses are fabricated on said substrate or individually fabricated using SiO 2, siN or a polymeric material and then adhered or bonded to said substrate.
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