Device and method for preparing porous silicon based on electrochemical corrosion of four-inch silicon substrate

Abstract

The invention belongs to the technical field of porous silicon preparation, and particularly relates to a device and method for preparing porous silicon based on electrochemical corrosion of a four-inch silicon substrate, and the device comprises a first fixed knob, a first placement groove, a corrosion groove body, a second placement groove, a positive electrode, a negative electrode, a second fixed knob and a corrosion solution fixing cover; corrosion tank fixing ports in the first placing tank and the second placing tank are in threaded connection with electrode tank fixing ports in the two ends of the corrosion tank body respectively, fixing knob fixing ports are formed in the first placing tank and the second placing tank, and the first placing tank is in threaded connection with a first fixing knob through the fixing knob fixing ports. And the second placing groove is in threaded connection with the second fixed knob through the fixed knob fixing interface. The corrosion positive electrode is in direct contact with the silicon wafer, a layer of aluminum electrode is sputtered on the back surface of the silicon wafer to increase the conductivity, and meanwhile, the four-inch platinum electrode is used as the corrosion negative electrode on the other side, so that the positive and negative electrodes are in forward parallel contact during corrosion.

Description

Technical Field

[0001] This invention belongs to the field of porous silicon preparation technology, specifically relating to an apparatus and method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate. Background Technology

[0002] Nanoporous silicon, due to its large specific surface area and high reactivity, possesses excellent luminescent properties and can be used as a photodetector in the field of photoelectric detection. Its nanostructure has high thermal conductivity, making it applicable to thermoelectric fields, and it has been widely used in lithium-ion battery anodes in recent years. Under certain triggering conditions, it can undergo a strong oxidation reaction with oxidants to release heat, making it widely used in energetic materials. Currently, the etching of nanoporous silicon substrates mainly uses two methods: metal-assisted chemical etching and electrochemical anodizing.

[0003] Metal-assisted chemical etching (MEC) involves depositing noble metal nanoparticles onto a silicon surface, followed by etching in an aqueous hydrofluoric acid solution, requiring no external power source. However, this method suffers from uneven etching, with poor control over the etching thickness across the entire surface. While simple and low-cost, it is suitable for complex structures and large-area fabrication. However, controlling the uniformity and perpendicularity of the pore structure presents significant challenges. Electrochemical etching involves immersing the silicon substrate in an electrolyte (typically aqueous or ethanol-HF electrolyte) and applying a current or voltage for a specific time. All reactions occur within a Teflon container, and the etching thickness can be controlled by adjusting the etching time and current density. This method is mature, but its fabrication efficiency is low, as it can only etch diced silicon wafers in a single pass, making repeated fabrication difficult and resulting in high costs.

[0004] Most existing fabrication processes are based on electrochemical etching. Existing patent CN 118996595A provides an electrochemical etching method, which, while indicating its suitability for large-size silicon wafers, is actually used in fabrication with 2cm*2cm wafers and a thickness of 525μm. The resulting etching depth is only 3.5μm-4.5μm, a depth ratio of only 1 / 100. The only drawback is the small wafer size; wafer-level fabrication is not achieved. Furthermore, these methods are difficult to implement for large-scale or array-type structures and are difficult to integrate with MEMS wafer-level fabrication processes, resulting in low process maturity. Summary of the Invention

[0005] The existing electrochemical etching devices typically place the positive and negative electrodes in the etching solution, and the electrodes need to be aligned before etching. When there is a positional deviation between the positive and negative electrodes, the current cannot pass through the silicon wafer in the forward direction, resulting in problems such as uneven etching depth and poor consistency of the fabrication process. This invention provides a device and method for preparing porous silicon based on the electrochemical etching of a four-inch silicon substrate. It realizes the preparation of a four-inch wafer-level porous silicon wafer in a single process, with an etching depth of 130-140μm and consistent etching uniformity. The maturity of the porous silicon fabrication process is effectively improved, and it has high compatibility with subsequent wafer-level hot-wire magnetron sputtering processes in the energetic field.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: An apparatus for preparing porous silicon using electrochemical etching on a four-inch silicon substrate includes a first fixing knob, a positive electrode, a first placement groove, an etching tank, a second placement groove, a negative electrode, a second fixing knob, and an etching solution fixing cap. Both the first and second placement grooves are provided with etching tank fixing interfaces. The etching tank body has electrode groove fixing ports at both ends. The etching tank fixing interfaces on the first and second placement grooves are threadedly connected to the electrode groove fixing ports at both ends of the etching tank body. Both the first and second placement grooves are provided with fixing knob fixing interfaces. The first placement groove is connected to... The first fixing knob is threadedly connected to the fixing interface of the fixing knob, and the second placement slot is threadedly connected to the fixing interface of the fixing knob. A rubber pad, a silicon wafer, and a positive electrode are sequentially arranged in the first placement slot, while a rubber ring and a negative electrode are arranged in the second placement slot. A metal coating layer is provided on the back of the silicon wafer, and it is in close contact with the positive electrode. The first fixing knob is electrically connected to the positive electrode, and the second fixing knob is electrically connected to the negative electrode, for connecting to an external DC power source. The etching tank has an etching solution injection port, and the etching solution fixing cap is threadedly connected to the etching solution injection port.

[0007] The corrosion tank, the first placement tank, the second placement tank, and the corrosion solution fixing cover are all made of polytetrafluoroethylene, and the first fixing knob and the second fixing knob are made of copper.

[0008] Both the positive and negative electrodes are platinum electrodes, with dimensions matching the silicon wafer and arranged in a positive parallel orientation; the thickness of both the positive and negative electrodes is 1 mm.

[0009] The silicon wafer is a four-inch P-type single-crystal silicon wafer with a resistivity of 4-6 Ω·m and a thickness of 525 μm; the metal coating layer is a platinum layer with a thickness of 100 nm.

[0010] The rubber pad has a porous silicon etching region of a preset shape, and the diameter of the porous silicon etching region is 10mm.

[0011] A method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate includes the following steps: S1. Silicon wafer pretreatment: Select a silicon substrate and deposit a metal coating layer on its back side to obtain a pretreated silicon wafer; S2. Device assembly: The rubber pad, pretreated silicon wafer and positive electrode are sequentially placed into the first placement slot, the rubber ring and negative electrode are placed into the second placement slot, the first placement slot and the second placement slot are connected to the electrode slot fixing ports at both ends of the corrosion tank body through their respective fixing interfaces with the corrosion tank, and then fixed and sealed by the first fixing knob and the second fixing knob respectively. S3. Preparation of etching solution: Mix anhydrous ethanol and hydrofluoric acid in a certain volume ratio to obtain the etching solution; S4. Corrosion solution injection: Inject the corrosion solution into the corrosion tank through the corrosion solution injection port, and tighten the corrosion solution fixing cap to seal it. S5. Electrochemical corrosion: Connect the first and second fixing knobs to the positive and negative terminals of the DC source respectively to form a corrosion circuit. Set the corrosion current density and corrosion time to perform electrochemical corrosion. S6. Post-processing: After etching is completed, pour out the etching solution, clean the etching tank and silicon wafer with anhydrous ethanol, and cut the silicon wafer to obtain porous silicon.

[0012] The volume ratio of anhydrous ethanol to hydrofluoric acid in S3 is 1:3.

[0013] The corrosion current density in S5 is 40-60 mA / cm2, and the corrosion time is 20-40 min.

[0014] In S6, custom cutting of the silicon wafer can realize the fabrication of arrayed energetic silicon wafers, and the shape of the porous silicon etching region (12) of the rubber pad (11) can be customized.

[0015] Compared with the prior art, the beneficial effects of this invention are: 1. This invention achieves parallel contact between the positive and negative electrodes during corrosion by directly contacting the silicon wafer with the positive electrode and sputtering an aluminum electrode layer on the back of the silicon wafer to increase conductivity, while using a four-inch platinum electrode as the negative electrode on the other side. This avoids oblique corrosion and avoids the problem of inconsistent corrosion depth caused by electrode misalignment in traditional electrochemical corrosion devices. Furthermore, the porous silicon wafers produced in a single batch have high consistency.

[0016] 2. This invention incorporates a rubber pad between the silicon wafer and the etching chamber. By processing rubber pads of different shapes, the contact area between the etching solution and the silicon wafer can be controlled, achieving the goal of customized design for energetic regions. This enables array etching and etching of special shapes. Furthermore, replacing the rubber pad eliminates the need to re-examine the parameters during the etching process, resulting in better consistency in the prepared porous silicon. Simultaneously, it provides a sealing effect, preventing the etching solution from leaking out during etching.

[0017] 3. This invention can etch multiple porous silicon wafers on a four-inch silicon substrate in one go, and the consistency of a single preparation is good, which is conducive to repeated experiments. Furthermore, it is compatible with subsequent hot-wire sputtering MEMS processes, effectively improving the preparation efficiency and process of porous silicon wafers, which is beneficial for subsequent large-scale applications. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the corrosion tank structure of the present invention; Figure 3 This is a schematic diagram of the structure of the first and second placement slots of the present invention; Figure 4 This is a schematic diagram of the structure of the rubber pad of the present invention; Figure 5 This is a photograph of the porous silicon prepared according to the present invention. Figure 6 for Figure 5 A magnified scanning electron microscope image of region 1 in the middle; Figure 7 for Figure 5 A magnified scanning electron microscope image of region 2 in the middle; Figure 8 for Figure 5 Magnified scanning electron microscope image of region 3 in the middle; Figure 9 These are scanning electron microscope (SEM) images of porous silicon with an etching time of 10 min, as shown in this invention. Figure 10 These are scanning electron microscope (SEM) images of porous silicon with an etching time of 20 min, as shown in this invention. Figure 11 These are scanning electron microscope (SEM) images of porous silicon with an etching time of 30 min, as shown in this invention. Figure 12 These are scanning electron microscope (SEM) images of porous silicon with an etching time of 40 min, as shown in this invention. Figure 13 This is a scanning electron microscope image of porous silicon with a corrosion current density of 10 mA / cm², as shown in this invention. Figure 14 This is a scanning electron microscope image of porous silicon with a corrosion current density of 20 mA / cm², as shown in this invention. Figure 15 This is a scanning electron microscope image of porous silicon with a corrosion current density of 30 mA / cm², as shown in this invention. Figure 16 This is a scanning electron microscope image of porous silicon with a corrosion current density of 40 mA / cm², as shown in this invention. Figure 17 This is a scanning electron microscope image of porous silicon with a corrosion current density of 50 mA / cm², as shown in this invention. Figure 18 This is a scanning electron microscope image of porous silicon with a corrosion current density of 60 mA / cm2 according to the present invention.

[0021] Wherein: 1 is the first fixing knob, 2 is the first placement slot, 3 is the etching tank body, 4 is the second placement slot, 5 is the second fixing knob, 6 is the etching solution fixing cover, 7 is the etching solution injection port, 8 is the electrode tank fixing port, 9 is the etching tank fixing interface, 10 is the fixing knob fixing interface, 11 is the rubber pad, and 12 is the porous silicon etching area. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] Example 1 This embodiment discloses an apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate, such as... Figure 1-4 As shown, the following details the specific dimensions, assembly relationships, and material properties: The device in this embodiment includes a first fixing knob 1, a first placement slot 2, an etching tank 3, a second placement slot 4, a positive electrode, a negative electrode, a second fixing knob 5, and an etching solution fixing cover 6. The etching tank fixing interfaces 9 of the first placement slot 2 and the second placement slot 4 are both externally threaded, while the electrode slot fixing ports 8 at both ends of the etching tank 3 are matching internally threaded with a thread specification of M40×1.5, ensuring a tight connection and convenient assembly / disassembly. The fixing knob fixing interfaces 10 of the first placement slot 2 and the second placement slot 4 are also internally threaded, adapting to the external threads of the first fixing knob 1 and the second fixing knob 5, achieving a sealed fixing of the components by tightening.

[0027] Furthermore, preferably, the corrosion tank 3, the first placement tank 2, the second placement tank 4, and the corrosion solution fixing cover 6 are all made of polytetrafluoroethylene (PTFE). This material is resistant to strong corrosive media such as hydrofluoric acid and has good insulation properties, preventing stray currents during the corrosion process. The first fixing knob 1 and the second fixing knob 5 are made of copper. Copper has excellent conductivity, ensuring a stable electrical connection with the electrodes, while also meeting the mechanical strength requirements for fixing.

[0028] Furthermore, preferably, both the positive and negative electrodes are platinum electrodes, perfectly matched to the four-inch silicon wafer, with a diameter of 101.6 mm (standard four-inch size) and a thickness of 1 mm. The two electrodes are arranged parallel to each other in the same direction, with the spacing adapted to the length of the etching tank 3 to ensure uniform distribution of the etching current. The silicon wafer is a four-inch P-type monocrystalline silicon wafer with a resistivity of 4-6 Ω·m and a thickness of 525 μm. A 100 nm thick platinum metal coating is deposited on its back side. This coating layer is tightly bonded to the positive electrode, which can significantly improve the conductivity of the silicon wafer and avoid uneven etching caused by contact resistance.

[0029] Furthermore, preferably, the rubber pad 11 in the first placement tank 2 is made of fluororubber, which has strong corrosion resistance and good elasticity. Its pre-set porous silicon etching area 12 has a diameter of 10mm. Through the isolation effect of the rubber pad 11, only the target area of ​​the silicon wafer comes into contact with the etching solution. The rubber ring in the second placement tank 4 is also made of fluororubber, used to seal the negative electrode with the second placement tank 4 and prevent leakage of the etching solution. The etching solution injection port 7 of the etching tank body 3 has an external thread structure, which mates with the internal thread of the etching solution fixing cap 6. Tightening it achieves a seal, preventing leakage of hydrofluoric acid gas during the etching process.

[0030] Assembly process: Sequentially place the rubber pad 11, the pre-treated silicon wafer (with the back coating layer facing the positive electrode), and the positive electrode into the first placement groove 2, ensuring that the silicon wafer and the positive electrode are tightly fitted without gaps; place the rubber ring and the negative electrode into the second placement groove 4, ensuring that the negative electrode is centered; align the etching groove fixing interface 9 of the first placement groove 2 with the electrode groove fixing port 8 at one end of the etching groove body 3, and tighten clockwise until sealed; similarly, connect and fix the second placement groove 4 to the other end of the etching groove body 3; screw the first fixing knob 1 and the second fixing knob 5 into the corresponding fixing knob fixing interface 10 until the electrode and silicon wafer are pressed tightly, ensuring a tight seal; check the sealing of each connection part to ensure no gaps, and then complete the overall assembly of the device.

[0031] Example 2 This embodiment uses the above-described apparatus to prepare porous silicon, and the specific steps are as follows: S1, Silicon Wafer Pretreatment A four-inch P-type single-crystal silicon wafer (resistivity 4-6 Ω·m, thickness 525 μm) was selected, and a platinum metal coating layer was deposited on its back side using magnetron sputtering. The coating thickness was controlled to be 100 nm. During the coating process, the vacuum degree was maintained at 5 × 10⁻⁴ Pa, the sputtering power was 150 W, and the deposition time was 30 min to ensure that the coating layer was uniform, dense, and firmly bonded to the silicon wafer, thus obtaining a pre-treated silicon wafer.

[0032] S2, Device Assembly Assemble each component according to the device assembly process in Example 1, focusing on ensuring tight contact between the silicon wafer and the positive electrode, as well as the sealing performance of each threaded connection, to avoid leakage or poor current contact during subsequent corrosion.

[0033] S3, Preparation of Corrosion Solution The etching solution was prepared in a fume hood by mixing anhydrous ethanol and hydrofluoric acid at a volume ratio of 1:3. The mixture was stirred slowly during the mixing process to prevent a large amount of gas generated by the evaporation of hydrofluoric acid from overflowing. After the preparation was completed, the mixture was allowed to stand for 5 minutes to ensure that it was mixed evenly, and the etching solution was obtained.

[0034] S4, Corrosion solution injection The prepared etching solution is injected into the etching tank 3 through the etching solution injection port 7. The injection volume is based on completely immersing the etching area of ​​the silicon wafer (about 50mL). Then, the etching solution fixing cap 6 is tightened clockwise to achieve a seal.

[0035] S5, Electrochemical Corrosion Connect the first fixing knob 1 to the positive terminal of the DC source via a wire, and the second fixing knob 5 to the negative terminal of the DC source via a wire, forming a complete etching circuit. Set the etching parameters according to the preparation requirements: etching current density of 40 mA / cm² (optimal parameter), etching time of 30-40 min, and maintain a stable DC source output during etching to avoid current fluctuations affecting the etching effect. Under these parameters, the etching current passes uniformly through the etching area of ​​the silicon wafer, achieving directional etching.

[0036] S6, Post-processing After etching, first loosen the etching solution fixing cap 6 in the fume hood to slowly release the residual gas in the tank, then pour all the etching solution into a dedicated waste liquid collection container. Next, inject anhydrous ethanol into the etching tank 3, soak for 5 minutes, then pour it out. Repeat the rinsing process three times to ensure thorough removal of residual etching solution. Remove the silicon wafer, rinse the surface with anhydrous ethanol, and place it on clean filter paper to air dry naturally (or dry in a drying oven). Finally, use a slicing machine to cut the silicon wafer into a 2×2 array structure to obtain a porous silicon product with a single diameter of 10mm. The etching depth is 130-140μm, the etching ratio is greater than 1 / 5, and the etching uniformity is good.

[0037] If it is necessary to prepare porous silicon of different sizes, the rubber pad 11 with the corresponding shape and size of porous silicon etching region 12 can be replaced. Array etching or special shape etching can be achieved without adjusting other process parameters.

[0038] To observe whether the etching depth is consistent, individual porous silicon wafers are cut out, such as... Figure 5 Three different regions (1, 2, and 3) in porous silicon were observed using a scanning electron microscope (SEM) at a magnification of 1000x. The images of a single silicon wafer and the SEM image are shown below. Figure 6-8 As shown.

[0039] The electron microscope images show that the etching depth of the silicon wafer is between 130 and 140 μm, with an etching ratio greater than 1 / 5, which is a significant improvement in etching depth compared to existing technologies.

[0040] To investigate the optimal corrosion parameters, the effects of different current densities and corrosion times on the preparation of porous silicon were studied. The porous silicon surface after corrosion was characterized primarily by SEM (scanning electron microscopy). Corrosion times were set to 10 min, 20 min, 30 min, and 40 min, respectively. SEM images of the porous silicon at different corrosion times are shown below. Figure 9-12 As shown.

[0041] When the corrosion time is short, the pore size is small and the number is small. As the corrosion time increases, the number of corrosion pores increases. As the corrosion time further increases, the corrosion surface becomes uneven. Therefore, the corrosion time is 30min-40min.

[0042] The effect of corrosion current density was investigated in the next step. Corrosion current densities were set at 10 mA / cm², 20 mA / cm², 30 mA / cm², 40 mA / cm², 50 mA / cm², and 60 mA / cm². Electron micrographs at each corrosion current density are shown below. Figure 13-18 As shown.

[0043] When the corrosion current is low, no obvious pores can be observed at a magnification of 30,000. As the corrosion current gradually increases, the pores of the porous silicon become denser and the pore size decreases. Therefore, the silicon film generated at a current density of 40 mA / cm² is relatively uniform. The optimal parameters for the corrosion process were determined through the above experiments.

[0044] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. An apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate, characterized in that: The system includes a first fixing knob (1), a positive electrode, a first placement slot (2), an corrosion tank (3), a second placement slot (4), a negative electrode, a second fixing knob (5), and a corrosion solution fixing cap (6). The first placement slot (2) and the second placement slot (4) are each equipped with a corrosion tank fixing interface (9). The corrosion tank body (3) has electrode slot fixing ports (8) at both ends. The corrosion tank fixing interfaces (9) on the first placement slot (2) and the second placement slot (4) are threadedly connected to the electrode slot fixing ports (8) at both ends of the corrosion tank body (3). The first placement slot (2) and the second placement slot (4) are each equipped with a fixing knob fixing interface (10). The first placement slot (2) is fixed by a fixing knob. The knob fixing interface (10) is threadedly connected to the first fixing knob (1), and the second placement slot (4) is threadedly connected to the second fixing knob (5) through the fixing knob fixing interface (10); the first placement slot (2) is provided with a rubber pad (11), a silicon wafer and a positive electrode in sequence, and the second placement slot (4) is provided with a rubber ring and a negative electrode; the back of the silicon wafer is provided with a metal coating layer and is in close contact with the positive electrode; the first fixing knob (1) is electrically connected to the positive electrode, and the second fixing knob (5) is electrically connected to the negative electrode for connecting to an external DC power source; the etching tank (3) is provided with an etching liquid injection port (7), and the etching solution fixing cover (6) is threadedly connected to the etching liquid injection port (7).

2. The apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 1, characterized in that: The corrosion tank (3), the first placement tank (2), the second placement tank (4) and the corrosion solution fixing cover (6) are all made of polytetrafluoroethylene, and the first fixing knob (1) and the second fixing knob (5) are made of copper.

3. The apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 1, characterized in that: Both the positive and negative electrodes are platinum electrodes, with dimensions matching the silicon wafer and arranged in a positive parallel orientation; the thickness of both the positive and negative electrodes is 1 mm.

4. The apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 1, characterized in that: The silicon wafer is a four-inch P-type single-crystal silicon wafer with a resistivity of 4-6 Ω·m and a thickness of 525 μm; the metal coating layer is a platinum layer with a thickness of 100 nm.

5. The apparatus for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 1, characterized in that: The rubber pad (11) has a porous silicon etching region (12) of a preset shape, and the diameter of the porous silicon etching region (12) is 10 mm.

6. A method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate, characterized in that, The apparatus according to any one of claims 1-5 comprises the following steps: S1. Silicon wafer pretreatment: Select a silicon substrate and deposit a metal coating layer on its back side to obtain a pretreated silicon wafer; S2. Assembly of the device: The rubber pad (11), the pretreated silicon wafer and the positive electrode are sequentially placed into the first placement groove (2), the rubber ring and the negative electrode are placed into the second placement groove (4), the first placement groove (2) and the second placement groove (4) are connected to the electrode groove fixing ports (8) at both ends of the corrosion tank body (3) through their respective fixing interfaces (9) with the corrosion tank, and then fixed and sealed by the first fixing knob (1) and the second fixing knob (5); S3. Preparation of etching solution: Mix anhydrous ethanol and hydrofluoric acid in a certain volume ratio to obtain the etching solution; S4. Injection of corrosion solution: Inject the corrosion solution into the corrosion tank (3) through the corrosion solution injection port (7) and tighten the corrosion solution fixing cap (6) to seal it. S5. Electrochemical corrosion: Connect the first fixed knob (1) and the second fixed knob (5) to the positive and negative terminals of the DC source respectively to form a corrosion circuit. Set the corrosion current density and corrosion time to carry out electrochemical corrosion. S6. Post-processing: After etching is completed, pour out the etching solution, clean the etching tank (3) and silicon wafer with anhydrous ethanol, and cut the silicon wafer to obtain porous silicon.

7. The method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 6, characterized in that: The volume ratio of anhydrous ethanol to hydrofluoric acid in S3 is 1:

3.

8. The method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 6, characterized in that: The corrosion current density in S5 is 40-60 mA / cm2, and the corrosion time is 20-40 min.

9. The method for preparing porous silicon based on electrochemical etching of a four-inch silicon substrate according to claim 6, characterized in that: In S6, custom cutting of the silicon wafer can realize the fabrication of arrayed energetic silicon wafers, and the shape of the porous silicon etching region (12) of the rubber pad (11) can be customized.

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