An ultra-thin silicon-based heat plate and a preparation method thereof

Abstract

The application belongs to the technical field of phase change heat transfer, and provides an ultrathin silicon-based uniform heating plate and a preparation method, which comprises an upper cover plate and a lower cover plate, the upper cover plate and the lower cover plate are connected to form a steam cavity, the condensation end wick of the upper cover plate is processed by using a femtosecond laser line scanning technology to form a hydrophilic / hydrophobic composite array with hydrophilic microgrooves and hydrophobic microridges covered with a low surface energy coating, which can promote the directional backflow of the condensed liquid working medium, so that the liquid working medium can more easily backflow to the evaporation end wick. The evaporation end wick of the lower cover plate is processed by using the femtosecond laser line scanning technology to generate a micro-nanometer level hydrophilic pore chain structure, which can realize isotropic diffusion, increase the heat transfer area and improve the uniformity of heat absorption. The application can effectively solve the contact thermal resistance and interface bonding force problems between the micro-nano structure and the substrate by ablation and induction of micro-nano structure size on the material surface of the semiconductor wafer substrate material through the femtosecond laser line scanning technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phase change heat transfer, and particularly relates to an ultrathin silicon-based uniform heating plate and a preparation method. BACKGROUND

[0002] The rapid development of microelectronic technology promotes the evolution of electronic components to ultra-high integration density, resulting in an exponential increase in the heat flux density per unit area. The local heat flux generated by current miniaturized electronic components in a narrow space has broken through 200 W / cm², far exceeding the carrying limit of traditional air cooling and liquid cooling heat dissipation technologies. The thermal accumulation effect caused by this high heat flux density not only causes the temperature of electronic components to exceed the safety threshold of 120℃, but also causes thermal stress damage to semiconductor materials, seriously threatening the operation reliability and service life of electronic equipment. As a new type of phase change heat transfer device, the uniform heating plate has become a core technology path to solve the problem of microelectronic heat dissipation, with its ultra-high thermal conductivity, millisecond-level thermal response speed, and millimeter-level thickness adaptability.

[0003] The uniform heating plate is a passive-driven thermal management system based on gas-liquid two-phase phase change heat transfer. Its working principle is essentially to realize high-efficiency heat transfer through the synergistic effect of phase change latent heat and capillary force of the working medium. A typical uniform heating plate is composed of a vacuum sealed cavity, a micro-nano structure wick, and a phase change working medium. When the evaporation end absorbs the heat load of the chip, the working medium vaporizes, and the generated vapor molecules diffuse to the condensation end along the cavity under the driving of the pressure difference. In the condensation area, the vapor releases latent heat and liquefies through interface contact, and the liquid working medium returns to the evaporation end under the action of the capillary force of the wick, forming a self-sustaining phase change heat transfer cycle. The heat transfer performance, efficiency and limit of the capillary wick mainly depend on the dynamic balance between the capillary pressure and the permeation rate of the working medium.

[0004] In the prior art, copper, aluminum and other metals are often used as materials to process the uniform heating plate. There is a significant difference in the thermal expansion coefficient between the metal-based uniform heating plate and the semiconductor chip, and a low thermal conductivity thermal interface material needs to be introduced for mechanical buffering during packaging, but this will significantly increase the interface contact thermal resistance, and also cause problems such as chip die warping and thermal stress concentration. Secondly, traditional ultrathin uniform heating plates use mechanical manufacturing processes such as wire mesh weaving, powder sintering and high-temperature brazing, and the thickness limit is difficult to break through the threshold of 0.5 mm. Although laser processing can prepare hydrophilic, super-hydrophilic, hydrophobic and super-hydrophobic structures on metal substrates, the existing technology is still limited to metal materials and the device thickness is rarely ≤0.5 mm. At the same time, when the thickness of the uniform heating plate is compressed to sub-millimeter level, i.e. <0.5 mm, it is still a great challenge to synergistically optimize the super-wetting characteristics, capillary driving force and nucleate boiling nucleation density in the ultrathin space.

[0005] Therefore, how to prepare the wicking structure of the isotropic capillary diffusion of the evaporation end and the anisotropic directional return flow of the condensation end of the vapor chamber, meet the heterogeneous needs of gas-liquid two-phase transport, and realize the intrinsic reduction of the interface contact thermal resistance of the sub-millimeter thickness silicon-based vapor chamber in semiconductor packaging is a technical problem that needs to be solved in the field. SUMMARY

[0006] The present application provides an ultrathin silicon-based vapor chamber and a preparation method, aiming to solve the above technical problems.

[0007] The present application is implemented as follows: an ultrathin silicon-based vapor chamber, comprising an upper cover plate and a lower cover plate, the inner side surface of the upper cover plate is provided with a condensation end wicking core, the condensation end wicking core is processed with an array of hydrophilic microgrooves, hydrophobic micro ridges are formed between adjacent hydrophilic microgrooves, and the top surface of the hydrophobic micro ridges is covered with a low surface energy coating; the inner side surface of the lower cover plate is provided with an evaporation end wicking core, the evaporation end wicking core is processed with a hydrophilic hole chain structure; the upper cover plate and the lower cover plate are connected to form a vapor cavity, and the upper cover plate and the lower cover plate are silicon-based plates.

[0008] Further, the interior of the hydrophilic microgroove is formed with a cotton-like particle structure.

[0009] Further, the surface of the hydrophilic hole chain structure is connected with a villus structure.

[0010] Further, the low surface energy coating is one of fluorocarbon resin, silicone resin, fluorosilicon copolymer and polysilazane hybrid material.

[0011] Further, a flange is formed around the inner side surface of the upper cover plate, the flange on one side is provided with a liquid filling hole, and the liquid filling hole communicates with the vapor cavity.

[0012] The present application also provides a preparation method of the above-mentioned ultrathin silicon-based vapor chamber, comprising preparing a low surface energy coating on the inner side surface of the upper cover plate, and then processing the condensation end wicking core with hydrophilic microgrooves and hydrophobic micro ridges on the inner side surface of the upper cover plate by femtosecond laser line scanning technology; processing the evaporation end wicking core with a hydrophilic hole chain structure on the inner side surface of the lower cover plate by femtosecond laser line scanning technology.

[0013] Further, the cotton-like particle structure is processed in the hydrophilic microgroove by femtosecond laser line scanning technology.

[0014] Further, the villus structure is processed on the surface of the hydrophilic hole chain structure by femtosecond laser line scanning technology.

[0015] Further, the low surface energy coating is prepared on the inner side surface of the upper cover plate by magnetron sputtering technology or thermal evaporation coating technology.

[0016] Further, the upper cover plate and the lower cover plate are connected by a dry silicon wafer bonding technology, which is one of glass frit, crystal-silicon eutectic, direct silicon fusion bonding and anodic bonding.

[0017] The beneficial effects of the present application include: the condensation end of the upper cover plate is treated by femtosecond laser line scanning technology to form a hydrophilic microgroove and a hydrophobic micro-ridge with a low surface energy coating, which can promote the directional return flow of the condensed liquid working medium, and the liquid working medium can more easily return to the evaporation end of the wick. The low surface energy coating can induce the formation of a pearl-shaped condensation mode with a larger heat transfer coefficient, and the dynamic condensation process of the droplet on the low surface energy coating and the surface energy released by the droplet merging can promote the droplet shedding of the upper cover plate, reduce the condensation thermal resistance of the condensation end, and improve the heat exchange performance.

[0018] The evaporation end of the lower cover plate is treated by femtosecond laser line scanning technology to produce a micro-nano level hydrophilic pore chain structure, which can realize isotropic diffusion, increase the heat transfer area and improve the uniformity of heat absorption. The hydrophilic pore chain structure can improve the capillary force, speed up the liquid replenishment and improve the critical heat flux. The micro-nano level hydrophilic pore chain structure has a large number of effective nucleation sites, which can promote the occurrence of nucleate boiling and improve the boiling heat transfer coefficient.

[0019] The present application processes a hydrophilic / hydrophobic composite array on the surface of a silicon wafer in an atmospheric environment by femtosecond laser line scanning technology, and the hydrophilic microgroove is covered with a nano-scale cotton-like particle structure, which can promote condensation nucleation and improve the directional transport capacity of the condensed droplets and the surface condensation heat transfer capacity.

[0020] The present application processes a micro-nano level hydrophilic pore chain structure on the surface of a silicon wafer in an atmospheric environment by femtosecond laser line scanning technology, and the surface of the hydrophilic pore chain structure is covered with a nano-scale bristle structure, which can improve the surface super-wetting and strengthen the capillary diffusion, increase the number of gasification nucleation points, and improve the surface heat transfer capacity.

[0021] The present application realizes the integration of semiconductor electronic devices and heat dissipation devices, and the micro-nano structure size is ablated and induced on the surface of the material by femtosecond laser line scanning technology on the semiconductor wafer substrate material, which can effectively solve the problem of contact thermal resistance and interface bonding force between the micro-nano structure and the substrate.

[0022] The present application can achieve a sub-millimeter level heat plate thickness and excellent heat dissipation effect, and has important application value in the high heat flux density device efficient heat dissipation of modern information communication technology, new energy automobile power system and high-speed rail transportation field. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1is a schematic diagram of the overall structure of the ultrathin silicon-based uniform heating plate provided by the embodiment of the present application.

[0024] Figure 2 is a front view of the ultrathin silicon-based uniform heating plate provided by the embodiment of the present application.

[0025] Figure 3 is Figure 2 a partial enlarged view.

[0026] Figure 4 is an SEM image of the evaporation end wick constructed by the embodiment 1 of the present application.

[0027] Figure 5 is Figure 4 an enlarged view of A in

[0028] Figure 6 is an SEM image of the condensation end wick constructed by the embodiment 1 of the present application.

[0029] Figure 7 is Figure 6 an enlarged view of B in

[0030] The labels in the figure respectively represent: 1 - upper cover plate, 2 - vapor cavity, 3 - lower cover plate, 4 - condensation end wick, 41 - hydrophilic micro groove, 42 - hydrophobic micro ridge, 43 - low surface energy coating, 44 - cotton-like particle structure, 5 - evaporation end wick, 51 - hydrophilic hole chain structure, 52 - villus structure, 6 - flange, 7 - liquid filling hole. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application more clear and understandable, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0032] As Figures 1-3 shown, the embodiment of the present application provides an ultrathin silicon-based uniform heating plate, which comprises an upper cover plate 1 and a lower cover plate 3. The inner side surface of the upper cover plate 1 is provided with a condensation end wick 4. The condensation end wick 4 is processed with an array of hydrophilic micro grooves 41. Adjacent hydrophilic micro grooves 41 form a hydrophobic micro ridge 42. The top surface of the hydrophobic micro ridge 42 is covered with a low surface energy coating 43. The inner side surface of the lower cover plate 3 is provided with an evaporation end wick 5. The evaporation end wick 5 is processed with a hydrophilic hole chain structure 51. The upper cover plate 1 and the lower cover plate 3 are connected to form a vapor cavity 2. The upper cover plate 1 and the lower cover plate 3 are silicon-based plates.

[0033] A flange 6 is formed around the inner side surface of the upper cover plate 1. A liquid filling hole 7 is formed in one side of the flange 6. The liquid filling hole 7 communicates with the vapor cavity 2. A liquid phase change working medium is injected into the vapor cavity 2.

[0034] The inner side surface of the upper cover plate 1 has a condensation end wick 4, which is processed with a micron-level array of hydrophilic microgrooves 41 and hydrophobic microridges 42, both of which form a hydrophilic / hydrophobic composite array, which is a strip array structure composed of a plurality of uniformly distributed rectangular grooves.

[0035] The inner side surface of the lower cover plate 3 has an evaporation end wick 5, which is processed with a micro-nano-level hydrophilic pore chain structure 51, which is a nested chain structure composed of micron-level and nano-level pores that are internally connected to each other.

[0036] As shown in Figures 4-7 , both the hydrophilic / hydrophobic composite array and the hydrophilic pore chain structure 51 have corresponding shape structure secondary laser-induced self-organized nanostructures, the corresponding shape structure secondary laser-induced self-organized nanostructures in the hydrophilic / hydrophobic composite array are strip-distributed cotton-like particle structures 44 composed of a plurality of nano-level protrusions uniformly distributed in the hydrophilic microgrooves 41. The corresponding shape secondary laser-induced self-organized nanostructures of the hydrophilic pore chain structure 51 are a plurality of nano-level fluff structures 52 uniformly distributed on the surface of the hydrophilic pore chain structure 51.

[0037] The hydrophilic / hydrophobic composite array on the inner side surface of the upper cover plate 1 is first prepared on the surface of a single crystal silicon wafer by a magnetron sputtering technique, a thermal evaporation coating technique or other coating techniques to form a low surface energy coating 43 with a low surface energy material to form a super-hydrophobic low surface energy coating 43, and then a femtosecond laser line scanning technique is used to process a super-hydrophilic hydrophilic microgroove 41, the pitch of the hydrophilic microgroove 41 is 30-150 μm, and the depth is 10-100 μm.

[0038] The laser power of the femtosecond laser line scanning technique for processing the hydrophilic / hydrophobic composite array is 0.01-2 W, the repetition frequency is less than or equal to 200 kHz, and the scanning speed is 5-50 mm / s. When the low surface energy coating 43 is prepared by a magnetron sputtering technique, specifically a radio frequency sputtering technique, the sputtering power is 100-200 W, the sputtering temperature is 80-220 ℃, the sputtering time is 10-40 min, and the working pressure is 0.4-3.5 Pa. The thickness of the low surface energy coating 43 is 0.5-2 μm, and the super-hydrophobic material used for the low surface energy coating can be selected from fluorocarbon resins, organic silicon resins, fluorosilicon copolymers, polysilazane hybrid materials and substances filled with nano-filler based on the above materials, wherein the fluorocarbon resin can be selected from polytetrafluoroethylene, the organic silicon resin can be selected from polydimethylsiloxane, the fluorosilicon copolymer can be selected from polytrifluoropropylmethylsiloxane, and the polysilazane hybrid material can be selected from perfluorooctyl-modified polysilazane.

[0039] The hydrophilic hole chain structure 51 of the inner side surface of the lower cover plate 3 is obtained by femtosecond laser line scanning technology, the inner side surface of the lower cover plate 3 is a super-hydrophilic surface, the nanohole chain spacing of the hydrophilic hole chain structure 51 is 1-10 microns, and the hole chain depth is less than 50 microns.

[0040] The laser power of the femtosecond laser line scanning technology for processing the hydrophilic hole chain structure 51 is 1-20 mW, the repetition frequency is 1-10 kHz, the scanning speed is 1-5 mm / s, and the spot size is 40 microns.

[0041] The cotton-like particle structure 44 inside the hydrophilic micro groove 41 and the villus structure 52 on the surface of the hydrophilic hole chain structure 51 are formed by ablation, remelting and induced self-formation in the laser processing process.

[0042] The upper cover plate 1 and the lower cover plate 3 are both wafer silicon materials and are in the form of flat plates, and the thickness is less than 1 mm; the inner side surface of the upper cover plate 1 has a flange 6 around the periphery; and the flange 6 of the upper cover plate 1 and the edge of the lower cover plate 3 are mutually attached and sealingly connected to form a vapor chamber 2.

[0043] The embodiment of the application also provides a preparation method of the above-mentioned ultra-thin silicon-based uniform heating plate, which comprises the following steps:

[0044] High-purity single crystal silicon wafers are selected as the upper cover plate and the lower cover plate, the upper cover plate and the lower cover plate are cut and cleaned, and the flange and the liquid filling hole are cut out from the upper cover plate.

[0045] The condensation end liquid absorption core of the upper cover plate is made, a low surface energy coating is sputtered on the inner side surface of the upper cover plate by magnetron sputtering technology, and the inner side surface of the upper cover plate is processed by femtosecond laser line scanning technology to ablate and form a hydrophilic / hydrophobic composite array.

[0046] The evaporation end liquid absorption core of the lower cover plate is made, and the inner side surface of the lower cover plate is processed by femtosecond laser line scanning technology to induce the formation of a micro-nano hydrophilic hole chain structure.

[0047] After the condensation end liquid absorption core of the upper cover plate and the evaporation end liquid absorption core of the lower cover plate are processed, they are ultrasonically cleaned in an ethanol and acetone environment for more than 5 minutes to remove surface-attached impurities, and then taken out and cleaned with deionized water and dried for standby use.

[0048] The flange of the upper cover plate and the edge of the lower cover plate are mutually attached and sealingly connected by dry silicon wafer bonding technology, which is one of glass frit, crystal-silicon eutectic, direct silicon fusion bonding and anode bonding.

[0049] A liquid filling pipe is connected to the liquid filling hole of the upper cover plate, liquid phase change working medium is injected into the vapor chamber through the liquid filling pipe and the liquid filling hole, after the liquid filling is completed, the liquid filling pipe is removed, and the liquid filling hole is sealed in the circumferential direction by using a welding or bonding method to ensure air tightness. The liquid phase change working medium is one of deionized water, electronic fluorination liquid, acetone, and methanol, and the vapor chamber is vacuumized before the liquid phase change working medium is injected.

[0050] The application will be further described in combination with specific examples.

[0051] Example 1

[0052] The application provides a preparation method of an ultrathin silicon-based uniform heating plate, including the following steps:

[0053] 9N purity single crystal silicon wafers are selected, and two 0.5 mm thick silicon plates in the form of flat plates are cut on the wafers as an upper cover plate and a lower cover plate. A flange and a liquid filling hole are cut on the upper cover plate.

[0054] A polytetrafluoroethylene coating is sputtered on the inner surface of the upper cover plate by using a magnetron sputtering technology, and then a condensation end wick with a hydrophilic micro groove and a hydrophobic micro ridge is processed on the inner surface of the upper cover plate by using a femtosecond laser line scanning technology. The laser power of the femtosecond laser line scanning technology is 0.03 W, the repetition frequency is 200 kHz, the scanning speed is 10 mm / s, and the scanning interval is 100 μm. The magnetron sputtering technology is radio frequency sputtering, the sputtering power is 150 W, the sputtering time is 30 min, the working temperature is 100 ℃, the argon flow rate is 50 sccm, and the working pressure is 3 Pa. The hydrophilic micro groove processed by the femtosecond laser line scanning technology has a width of 30 μm, an interval of 80 μm, and a depth of 40 μm, and contains a primary periodic arrangement of micron-level hydrophilic / hydrophobic composite arrays and a secondary continuous distribution of nanometer-level cotton-like particle structures along the hydrophilic micro groove.

[0055] An evaporation end wick with a hydrophilic hole chain structure is processed on the inner surface of the lower cover plate by using the femtosecond laser line scanning technology, and contains micro-nanometer-level hydrophilic hole chain structures and self-induced nanometer-level villus structures. The hole chain interval of the hydrophilic hole chain structure is 2 μm, the power of the femtosecond laser line scanning technology is 1.3 mW, the scanning interval is 8 μm, the repetition frequency is 1 kHz, the scanning speed is 1 mm / s, and the spot size is 40 μm.

[0056] The upper cover plate and the lower cover plate are ultrasonically cleaned in an ethanol and acetone environment for 10 min, and then taken out and cleaned with deionized water and dried.

[0057] The flange of the upper cover plate and the edge of the lower cover plate are mutually adhered and sealed by using a glass frit bonding technology.

[0058] The Sn-Ag solder is used to connect the liquid filling pipe to the liquid filling hole of the upper cover plate, the vapor cavity is connected to the vacuum pump, and the vacuum degree is less than 1 Pa, then the deionized water with a volume matching the volume of the vapor cavity is injected through the liquid filling pipe and the liquid filling hole, the liquid filling pipe is removed, and the Au-Sn solder is used to seal the liquid filling hole.

[0059] Example 2

[0060] The embodiment of the present application provides a preparation method of an ultrathin silicon-based heat plate.

[0061] 9N purity single crystal silicon wafers are selected, and two 0.5mm-thick silicon plates are cut from the wafers as an upper cover plate and a lower cover plate, and a flange and a liquid filling hole are cut from the upper cover plate.

[0062] A polydimethylsiloxane coating layer is formed on the inner surface of the upper cover plate by using a thermal evaporation coating technology, and then a condensation end wick with hydrophilic microgrooves and hydrophobic microridges is processed on the inner surface of the upper cover plate by using a femtosecond laser line scanning technology. The laser power of the femtosecond laser line scanning technology is 0.4W, the repetition frequency is 200kHz, the scanning speed is 10mm / s, and the scanning interval is 150μm. The thermal evaporation coating technology is that polydimethylsiloxane and a curing agent are spin-coated on the bottom of the glass cavity, the weight ratio of the polydimethylsiloxane to the curing agent is 10:1, the inner surface of the upper cover plate is placed 2mm above the polydimethylsiloxane and the curing agent, and the upper cover plate is placed in a muffle furnace and heated to 300℃ for 90min to obtain the upper cover plate covered with the polydimethylsiloxane coating layer. The hydrophilic microgrooves processed by the femtosecond laser line scanning technology have a width of 60μm, an interval of 100μm and a depth of 85μm, and contain a primary periodic arrangement of micron-level hydrophilic / hydrophobic composite arrays and a secondary continuous distribution of nanometer-level cotton-like particle structures along the hydrophilic microgrooves.

[0063] An evaporation end wick with a hydrophilic hole chain structure is processed on the inner surface of the lower cover plate by using the femtosecond laser line scanning technology, and contains micro-nanometer-level hydrophilic hole chain structures and self-induced nanometer-level villus structures. The hole chain interval of the hydrophilic hole chain structure is 3μm, the power of the femtosecond laser line scanning technology is 1.8mW, the scanning interval is 10μm, the repetition frequency is 1kHz, the scanning speed is 1mm / s, and the spot size is 40μm.

[0064] The upper cover plate and the lower cover plate are ultrasonically cleaned in ethanol and acetone environments respectively for 10min, and then taken out and cleaned with deionized water and dried.

[0065] The flange of the upper cover plate is matched and sealed to the edge of the lower cover plate by using a glass frit bonding technology.

[0066] Sn-Ag solder is used to connect the liquid filling pipe at the liquid filling hole of the upper cover plate, the steam cavity is connected to a vacuum pump, is evacuated to a vacuum degree <1 Pa, a volume of deionized water matching the volume of the steam cavity is injected through the liquid filling pipe and the liquid filling hole, the liquid filling pipe is removed, and the liquid filling hole is sealed using Au-Sn solder.

[0067] The above description is merely preferred embodiments of the present application, but not to limit the present application. Any modification, equivalent replacement and improvement made in the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. An ultra-thin silicon-based vapor chamber, characterized by, The application relates to a heat pipe, which comprises the following parts: an upper cover plate, an inner side surface of which is provided with a condensation end wick, the condensation end wick is processed with an array of hydrophilic microgrooves, and a hydrophobic microridge is formed between adjacent hydrophilic microgrooves, and a low surface energy coating is covered on the top surface of the hydrophobic microridge; a lower cover plate, an inner side surface of which is provided with an evaporation end wick, and the evaporation end wick is processed with a hydrophilic hole chain structure; the upper cover plate and the lower cover plate are connected to form a steam cavity, and the upper cover plate and the lower cover plate are silicon substrates.

2. The ultra-thin silicon-based uniform heating plate of claim 1, wherein, The hydrophilic microgrooves are internally formed with a cotton-like particle structure.

3. The ultra-thin silicon-based uniform heating plate of claim 2, wherein, The surface of the hydrophilic hole chain structure is connected with a villus structure.

4. The ultra-thin silicon-based uniform heating plate of claim 1, wherein, The low surface energy coating is one of fluorocarbon resin, organic silicon resin, fluorosilicon copolymer and polysilazane hybrid material.

5. The ultra-thin silicon-based uniform heating plate of claim 1, wherein, Flanges are formed around the inner side surface of the upper cover plate, and a liquid filling hole is formed in one of the flanges, and the liquid filling hole is communicated with the steam cavity.

6. The method of producing an ultra-thin silicon-based uniform heating plate according to any one of claims 1 to 5, characterized in that, The application further relates to a preparation method of the heat pipe. The low surface energy coating is prepared on the inner side surface of the upper cover plate, and then a condensation end wick with hydrophilic microgrooves and hydrophobic microridges is processed on the inner side surface of the upper cover plate through a femtosecond laser line scanning technology; an evaporation end wick with a hydrophilic hole chain structure is processed on the inner side surface of the lower cover plate through the femtosecond laser line scanning technology.

7. The method of claim 6, wherein the method further comprises: A cotton-like particle structure is processed in the hydrophilic microgrooves through the femtosecond laser line scanning technology.

8. The method of claim 6, wherein the method further comprises: A villus structure is processed on the surface of the hydrophilic hole chain structure through the femtosecond laser line scanning technology.

9. The method of claim 6, wherein the method further comprises: The low surface energy coating is prepared on the inner side surface of the upper cover plate through a magnetron sputtering technology or a thermal evaporation coating technology.

10. The method of claim 6, wherein the method further comprises: The upper cover plate and the lower cover plate are connected through a dry silicon wafer bonding technology, and the dry silicon wafer bonding technology is one of a glass frit, a crystal-silicon eutectic, direct silicon fusion bonding and anode bonding.

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