Three-dimensional trench silicon electrode detector and method of making same

Abstract

The application discloses a three-dimensional trench silicon electrode detector and a preparation method thereof. The detector is composed of a plurality of detection units. The detection unit comprises a silicon dioxide protective layer, an outer electrode arranged on the silicon dioxide protective layer, a silicon base and a center electrode arranged on the silicon dioxide protective layer and in the outer electrode. The silicon base comprises a base part and a nested part. The nested part is embedded in the outer electrode and located on the base part. The center electrode and the nested part are filled with an insulator between the center electrode and the outer electrode and between the nested part and the outer electrode. An electrode contact aluminum layer is arranged on the top of the outer electrode, the center electrode and the insulator. An electrode contact port is arranged on the electrode contact aluminum layer of the outer electrode and the center electrode. The application solves the problem that the existing detector has a small light absorption coefficient, a narrow absorption spectrum and cannot fully absorb and utilize solar energy.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detector technology and relates to a three-dimensional trench silicon electrode detector and its fabrication method. Background Technology

[0002] Currently, the application of silicon-based photodetectors faces the following problems. On the one hand, the performance of silicon-based photodetectors is limited by the photoelectric properties of silicon materials, making it impossible to integrate high-density light sources and low-loss high-speed photoelectric modulators. On the other hand, silicon-based photodetectors have a small absorption coefficient and a narrow absorption spectrum, and cannot absorb most infrared wavelengths, which greatly limits the widespread application of silicon-based photodetectors.

[0003] Two-dimensional photocatalytic materials possess abundant surface active sites, unique geometric structures, tunable electronic structures, and excellent photocatalytic activity, making them potentially valuable in the field of photoelectric detection. Therefore, this invention utilizes a ZnO / C2N heterojunction as the light-absorbing material in a photodetector to study a novel detector, and applies strain to the ZnO / C2N heterojunction to achieve efficient utilization of solar energy. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a three-dimensional trench silicon electrode detector, which solves the problems of existing detectors having a small light absorption coefficient, a narrow absorption spectrum, and being unable to fully absorb and utilize solar energy.

[0005] The present invention also provides a method for fabricating a three-dimensional trench silicon electrode detector. This method simplifies the overall fabrication process of the detector, realizes double-sided etching, effectively improves the electric field distribution, and eliminates the detection blind zone of the detector.

[0006] The technical solution adopted in this invention is a three-dimensional trench silicon electrode detector, which is composed of several detection units. Each detection unit includes a silicon dioxide protective layer with a quadrilateral cross-section. A hollow, straight quadrangular prism-shaped peripheral electrode is provided on the silicon dioxide protective layer. A silicon substrate and a central electrode are disposed on the silicon dioxide protective layer and inside the peripheral electrode. The silicon substrate includes a base portion and a nested portion. The cross-sectional dimensions of the base portion are the same as the cross-sectional dimensions of the silicon dioxide protective layer. The nested portion is embedded in the peripheral electrode and located on the base portion. An insulator is filled between the central electrode and the peripheral electrode, and between the nested portion and the peripheral electrode. An electrode contact aluminum layer is provided on the top of the peripheral electrode, the central electrode, and the insulator. An electrode contact port is provided on both the peripheral electrode and the central electrode electrode's electrode contact aluminum layers.

[0007] Another technical solution adopted in this invention is a method for fabricating a three-dimensional trench silicon electrode detector, comprising:

[0008] S1, Oxidation: Clean the oxidation furnace, take out the chip and place it vertically into the quartz stone. Under 1000℃ conditions, oxygen and silicon react chemically to generate silicon oxide.

[0009] S2, Marking and Photolithography: After the chip is coated with photoresist, it is placed under a photolithography machine and continuously fine-tuned to ensure that the markings on the chip precisely match the markings on the photomask; the aligned chip is exposed with ultraviolet light, and finally the detector pattern is transferred onto the chip and revealed by developing the detector pattern;

[0010] S3, Electrode fabrication: Under an environment of 20°C, hollow trenches are etched on the chip surface using ICP etching process. The etching depth is 80%-90% of the detector height. Impurity gas is added to SiH4 gas, and the mixed gas is chemically deposited in the trench, continuously diffusing to fill the trench and form an electrode. The electrode includes a central electrode (2) and a peripheral electrode (1). On the other side of the chip, a nested part (3) is etched and an electrode is fabricated, wherein the etching depth of the nested part (3) is 10% of the detector height.

[0011] S4, Annealing: Place the chip in an annealing furnace and anneal it for 30 minutes in a dry nitrogen atmosphere at 600°C.

[0012] S5, Electrode metallization: Metal is plated onto the electrode surface to facilitate subsequent pressure application;

[0013] S6, Packaging: The detector unit or array is drawn on the chip, the electrode points on the detector are soldered to the external pins with metal wires, and finally sealed and packaged with a plastic tube.

[0014] The beneficial effects of this invention are as follows: The introduction of a two-dimensional photocatalytic material ZnO / C2N heterojunction adjusts the light absorption range and intensity of monolayer ZnO and C2N. Constructing the ZnO / C2N heterojunction reduces the band gap of the two-dimensional material, and with this reduction, the light absorption range significantly expands, extending into the infrared region where a redshift occurs. The interlayer coupling in the ZnO / C2N heterostructure increases the light absorption intensity of the three-dimensional trench silicon electrode detector, ensuring the detector's full absorption and utilization of solar energy. The construction of the ZnO / C2N heterojunction in this invention can serve as a highly efficient means to adjust the light absorption range and intensity of monolayer ZnO and C2N, ensuring the photodetector's full utilization of solar energy. This invention also provides a method for fabricating a three-dimensional trench silicon electrode detector, which achieves double-sided etching of the entire detector, effectively improving the electric field distribution and eliminating the detection blind zone of the device. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a diagram of a three-dimensional trench silicon electrode detector array according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of a three-dimensional trench silicon electrode detector according to an embodiment of the present invention.

[0018] Figure 3 This is a side view of the three-dimensional trench silicon electrode detector structure according to an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the checkerboard-shaped protrusions on the upper end of the isolation silicon body in an embodiment of the present invention.

[0020] Figure 5 These are schematic diagrams of ZnO / C2N heterojunctions. Among them, (a) is a schematic diagram of the ZnO / C2N heterojunction of SC-I, (b) is a schematic diagram of the ZnO / C2N heterojunction of SC-II, and (c) is a schematic diagram of the ZnO / C2N heterojunction of SC-III.

[0021] Figure 6 These are absorption spectra of ZnO monomer, C2N monomer, and ZnO / C2N heterojunction.

[0022] Figure 7 This is the absorption spectrum of a ZnO / C2N heterojunction under strain conditions.

[0023] In the figure, 1. peripheral electrode, 2. central electrode, 3. nested part, 4. electrode contact aluminum layer, 5. silicon dioxide protective layer, 6. substrate part, 7. isolation silicon body. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] A three-dimensional trench silicon electrode detector, with the structure as follows: Figure 1 As shown, it is composed of an array of several detection units, and the structure of the detection unit is as follows: Figures 2-3As shown, it includes a silicon dioxide protective layer 5 with a quadrilateral cross-section. A hollow, straight quadrangular prism-shaped peripheral electrode 1 is provided on the silicon dioxide protective layer 5. A silicon substrate and a central electrode 2 are provided on the silicon dioxide protective layer 5 and inside the peripheral electrode 1. The silicon substrate includes a substrate portion 6 and a nested portion 3. The cross-sectional dimensions of the substrate portion 6 are the same as the cross-sectional dimensions of the silicon dioxide protective layer 5. The nested portion 3 is embedded in the peripheral electrode 1 and located on the substrate portion 6. An insulator 7 is filled between the central electrode 2 and the peripheral electrode 1, and between the nested portion 3 and the peripheral electrode 1. An electrode contact aluminum layer 4 is provided on the top of the peripheral electrode 1, the central electrode 2, and the insulator 7. An electrode contact port is provided on both the peripheral electrode 1 and the central electrode 2 electrode contact aluminum layers 4.

[0026] The peripheral electrode 1 of this invention is n + Heavy doped phosphorus silicon / p + Heavily doped boron silicon with a doping concentration of 10 18 ~5×10 19 cm -3 The central electrode 2 is p + Heavy doped borosilicate / n + Heavy doped phosphorus silicon, with a doping concentration of 10. 18 ~5×10 19 cm -3 The substrate 6 is a p-type lightly doped boron silicon with a doping concentration of 10. 12 ~10 14 cm -3 .

[0027] The three-dimensional trench silicon electrode detector of the present invention has a detector height of 300-500 μm, which can ensure that the particle generates a sufficiently strong signal upon incident. The silicon dioxide protective layer 5 has a thickness of 1 μm and serves a protective function. The substrate portion 6 has a height of 20-50 μm, which is intended to stabilize the mechanical structure of the device. The nested portion 3 has a height of 30-50 μm, and its height is 10% of the detector height. The outer electrode 1 has an electrode width of 10 μm. The central electrode 2 has an electrode diameter of 10 μm. The isolator 7 is a two-dimensional photocatalytic material ZnO / C2N heterojunction with a width of 50 μm. Since the charge collection performance of the detector is limited by the spacing between the unit electrodes, a spacing that is too large or too small will affect the large-area integration of its array. Therefore, the width of the isolator 7 in the present invention is selected as 50 μm.

[0028] like Figure 4 As shown, the top of the detector of the present invention has a checkerboard pattern of protrusions, wherein the protrusions and the four sides of each protrusion are square. Figure 4The shading represents the square protrusion, where each side measures 10 × 10 μm. The sum of the areas of the four sides of the protrusion is the increased surface area, denoted as S, which is S = 10 × 10 × 4 × 60 = 24000 (μm). 2 The original three-dimensional trench electrode silicon detector's top receiving surface area (minus the central electrode portion) is: 110 × 110 - π5 = 12021.5 (μm). 2 The comparison shows that the surface area of ​​the checkerboard-shaped protrusions on the top of the three-dimensional trench silicon electrode detector based on the two-dimensional photocatalytic material ZnO / C2N heterojunction of the present invention is about 3 times that of the original detector. Therefore, the three-dimensional trench silicon electrode detector based on the two-dimensional photocatalytic material ZnO / C2N heterojunction of the present invention can better absorb and utilize solar energy.

[0029] The three-dimensional trench silicon electrode detector of this invention has an isolator 7 that is a two-dimensional photocatalytic material ZnO / C2N heterojunction. This ZnO / C2N heterojunction is composed of a 5×5 ZnO supercell and a 2×2 C2N supercell, a combination that minimizes the influence of strain on the heterojunction. This invention constructs the ZnO / C2N heterojunction by fixing C2N and translating ZnO to a high-symmetry position, forming a ZnO / C2N heterojunction with three stacked structures (SC). During the construction of heterojunctions, the two-dimensional materials ZnO and C2N are affected by different end-face contact points, resulting in heterojunctions with different performance. This invention forms three stacked structures by fixing C2N and translating ZnO to a high-symmetry point. Calculations show that the SC-III type ZnO / C2N heterojunction has the lowest formation energy E. f and binding energy E b Therefore, the SC-III type ZnO / C2N heterojunction structure is more stable than the other two structures. The two-dimensional photocatalytic material of the insulator 7 in this invention adopts the SC-III type ZnO / C2N heterojunction. Strain is not only a common and unavoidable effect in heterojunctions, but also an effective means to change the physical properties of heterojunctions. Transverse strain can be used as an effective means to adjust the band gap and light absorption of the ZnO / C2N heterojunction, thereby realizing the effective utilization of solar energy by the photodetector.

[0030] Schematic diagrams of ZnO / C2N heterojunctions with three stacked structures (SC) are shown below. Figure 5 As shown, (a) is a schematic diagram of the ZnO / C2N heterojunction of SC-I, (b) is a schematic diagram of the ZnO / C2N heterojunction of SC-II, and (c) is a schematic diagram of the ZnO / C2N heterojunction of SC-III. It can be seen that the performance of the constructed ZnO / C2N heterojunction varies depending on the relative positions of the monomers ZnO and C2N. This patent selects the optimal ZnO / C2N heterojunction structure by constructing three different stacking structures.

[0031] Thermodynamic stability can be examined and determined to identify the most stable SC structure in a ZnO / C2N heterojunction. The binding energy E of the heterojunction is calculated using the following formula. b and formation energy E f :

[0032]

[0033]

[0034] In the above formula, E het S0 is the total energy of the ZnO / C2N heterojunction; S0 is the surface area of ​​the ZnO / C2N heterojunction; E0 is the total energy of the ZnO / C2N heterojunction. ZnO It is the energy of a single-layer ZnO; E C2N It is the energy of a single layer of C2N; E Zn E O E C E N M represents the average energy of a single atom Zn, O, C, and N in its most stable phase, respectively; Zn N O N C N N These represent the number of Zn, O, C, and N atoms in the ZnO / C2N heterojunction, respectively.

[0035] The calculation results for the ZnO / C2N heterojunctions of the three stacked structures (SC) are shown in Table 1:

[0036] Table 1. Lattice constant a, interlayer spacing d, and formation energy E of SC-Ⅰ, SC-Ⅱ, and SC-Ⅲ heterojunctions f Binding energy E b band gap E g Work function W f

[0037]

[0038] As shown in the table above, the SC-Ⅲ type ZnO / C2N heterojunction has the lowest formation energy F. f and binding energy E b Therefore, the SC-Ⅲ type ZnO / C2N heterojunction structure is more stable than the other two structures. The two-dimensional photocatalytic material of the insulator 7 of this invention adopts the SC-Ⅲ type ZnO / C2N heterojunction.

[0039] The utilization of solar energy begins with the generation of charge carriers under illumination; therefore, studying the optical response of ZnO / C2N heterojunctions is of great significance. The absorption coefficient α(ω) of the ZnO monolayer and C2N monolayer in the ZnO / C2N heterojunction can be obtained by the following formula:

[0040]

[0041] In the above formula, ε1(ω) is the real part of the dielectric function; ε2(ω) is the imaginary part of the dielectric function.

[0042] Two-dimensional photocatalytic heterostructures are designed and synthesized based on first-principles calculations (VASP). VASP can not only calculate the equilibrium structure and energy of various systems, but also accurately predict the electronic properties of materials and deeply analyze their various physicochemical properties. VASP uses periodic boundary conditions (or supercell models) and optimizes the geometry of various systems such as atoms, molecules, surfaces, and clusters based on density functional theory to obtain stable configurations, thereby obtaining various structural parameters, including the lattice constant of the stable configuration, the position of each atom, and the bond lengths and bond angles between atoms. The absorption spectra of its ZnO monomer, C2N monomer, and ZnO / C2N heterostructure are as follows: Figure 6 As shown in the figure, the absorption spectra of ZnO monomer, C2N monomer, and ZnO / C2N heterojunction are compared. Figure 6 It is known that the ZnO / C2N heterojunction has a smaller band gap, giving it a wider optical response range; the absorption coefficient of the ZnO / C2N heterojunction is higher than that of ZnO monomers and C2N monomers, and its coefficient can be increased to 1.2 × 10⁻⁶. 5 cm -1 In this process, the improved absorption performance of the ZnO / C2N heterojunction is closely related to the effective separation of charge carriers. Therefore, the construction of the ZnO / C2N heterojunction can serve as a highly efficient means to adjust the light absorption range and intensity of monolayer ZnO and C2N, thereby ensuring the full utilization of solar energy by the photodetector.

[0043] Strain is not only a common and unavoidable effect in heterojunctions, but also an effective means of altering their physical properties. This invention selects transverse strain to control the ZnO / C2N heterojunction, from -6% to 6%, with a step size of 2%. Figure 7 As shown. Figure 7 This indicates that lateral strain can alter the light absorption properties of the ZnO / C2N heterojunction, especially compressive strain, which can broaden the light response range and increase the absorption intensity. In conclusion, lateral strain can be an effective means of adjusting the band gap and light absorption of the ZnO / C2N heterojunction, thereby enabling photodetectors to effectively utilize solar energy.

[0044] This invention also provides a method for fabricating a three-dimensional trench silicon electrode detector:

[0045] S1, Oxidation: After cleaning the oxidation furnace, the chip is removed and vertically placed into quartz. At a high temperature of 1000℃, oxygen and silicon react chemically to generate silicon oxide. Dry oxidation produces Si + O₂ = SiO₂, while wet oxidation produces Si + 2H₂O = SiO₂ + 2H₂. Small amounts of hydrogen chloride and trichloroethylene are usually added as adsorption centers for impurities to improve the chip's performance. Oxidation eliminates surface leakage current and plays a protective role throughout the entire preparation process.

[0046] S2, Marking and Photolithography: After the chip is coated with photoresist, it is placed under a photolithography machine for continuous fine-tuning to ensure that the markings on the chip precisely match the markings on the photomask; the aligned chip is exposed to ultraviolet light, and finally the detector pattern is transferred onto the chip, which is then developed to reveal the detector pattern. Marking and photolithography can form detector units and array patterns on the chip.

[0047] S3, Electrode Fabrication: Under 20°C conditions, hollow trenches are etched on the chip surface using ICP etching, with an etching depth of 80%-90% of the detector height. Impurity gas is added to SiH4 gas, causing the mixed gas to chemically deposit in the trenches, continuously diffusing and filling the trenches to form electrodes. The electrodes include a central electrode 2 and peripheral electrodes 1. Since the detector of this invention requires double-sided etching, this step is repeated to etch a nested portion 3 on the other side of the chip and fabricate electrodes thereon, wherein the etching depth of the nested portion 3 is 10% of the detector height.

[0048] S4, Annealing: The chip is placed in an annealing furnace and annealed for 30 minutes in a dry nitrogen atmosphere at 600°C to remove defects.

[0049] S5, Electrode metallization: Metal is plated onto the electrode surface for subsequent pressure application.

[0050] S6, Packaging: The detector unit or array is drawn on the chip, the electrode points on the detector are soldered to the external pins with metal wires, and finally sealed and packaged with a plastic tube.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A three-dimensional trench silicon electrode detector, characterized in that, It is composed of several detection units. The detection unit includes a silicon dioxide protective layer (5) with a quadrilateral cross section. A hollow, straight quadrangular prism-shaped peripheral electrode (1) is provided on the silicon dioxide protective layer (5). A silicon substrate and a central electrode (2) are provided on the silicon dioxide protective layer (5) and inside the peripheral electrode (1). The silicon substrate includes a substrate part (6) and a nested part (3). The cross-sectional dimensions of the substrate part (6) are the same as the cross-sectional dimensions of the silicon dioxide protective layer (5). The nested part (3) is embedded in the peripheral electrode (1) and located on the substrate part (6). An insulator (7) is filled between the central electrode (2) and the peripheral electrode (1) and between the nested part (3) and the peripheral electrode (1). An electrode contact aluminum layer (4) is provided on the top of the peripheral electrode (1), the central electrode (2) and the insulator (7). An electrode contact port is provided on the two electrode contact aluminum layers (4) of the peripheral electrode (1) and the central electrode (2). The insulator (7) is a two-dimensional photocatalytic material ZnO / C2N heterojunction with a width of 50 μm; the ZnO / C2N heterojunction is composed of a 5×5 ZnO supercell and a 2×2 C2N supercell; The top of the detector has a checkerboard pattern of protrusions, wherein the protrusions and the four sides of each protrusion are square, and the size of each side of the square protrusion is 10×10μm.

2. The three-dimensional trench silicon electrode detector according to claim 1, characterized in that, The peripheral electrode (1) is p + Heavy doped borosilicate / n + Heavy doped phosphorus silicon, doping concentration of 10 18 ~5×10 19 cm -3 The substrate portion (6) is a p-type lightly doped borosilicate with a doping concentration of 10. 12 ~10 14 cm -3 .

3. The three-dimensional trench silicon electrode detector according to claim 1, characterized in that, The detector has a height of 300-500 μm; the silicon dioxide protective layer (5) has a thickness of 1 μm; the substrate (6) has a height of 20-50 μm; the nested part (3) has a height of 30-50 μm, and the height of the nested part (3) is 10% of the detector height; the outer electrode (1) has an electrode width of 10 μm; and the center electrode (2) has an electrode diameter of 10 μm.

4. The three-dimensional trench silicon electrode detector according to claim 1, characterized in that, A ZnO / C2N heterojunction is constructed by translating ZnO to a highly symmetric position using a fixed C2N layer.

5. A method for fabricating a three-dimensional trench silicon electrode detector as described in any one of claims 1-4, characterized in that, include: S1, Oxidation: Clean the oxidation furnace, take out the chip and place it vertically into the quartz stone. Under 1000℃ conditions, oxygen and silicon react chemically to generate silicon oxide. S2, Marking and Photolithography: After the chip is coated with photoresist, it is placed under a photolithography machine and continuously fine-tuned to ensure that the markings on the chip precisely match the markings on the photomask; the aligned chip is exposed with ultraviolet light, and finally the detector pattern is transferred onto the chip and revealed by developing the detector pattern; S3, Electrode fabrication: Under an environment of 20°C, hollow trenches are etched on the chip surface using ICP etching process, with an etching depth of 80%-90% of the detector height. Impurity gas is added to SiH4 gas, causing the mixed gas to chemically deposit in the trenches and continuously diffuse to fill the trenches to form electrodes. The electrodes include a central electrode (2) and a peripheral electrode (1). On the other side of the chip, a nested portion (3) is etched and electrodes are fabricated, wherein the etching depth of the nested portion (3) is 10% of the detector height. S4, Annealing: Place the chip in an annealing furnace and anneal it for 30 minutes in a dry nitrogen atmosphere at 600°C. S5, Electrode metallization: Metal is plated onto the electrode surface to facilitate subsequent pressure application; S6, Packaging: The detector unit or array is drawn on the chip, the electrode points on the detector are soldered to the external pins with metal wires, and finally sealed and packaged with a plastic tube.

6. The method for fabricating a three-dimensional trench silicon electrode detector according to claim 5, characterized in that, In S1, dry oxidation is... Si+O 2 =SiO 2 ， wet oxidation to Si + 2H 2 O=SiO 2 +2H 2 A small amount of hydrogen chloride and trichloroethylene are added as adsorption centers for impurities.

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