Excimer laser and LIGA process combined microporous structure processing method and system

Abstract

The invention relates to the technical field of microporous structure processing, and discloses an excimer laser and LIGA process combined microporous structure processing method and system, and the method comprises the following steps: S1, substrate pretreatment, S2, excimer laser photoetching, S3, development and electroforming mold preparation, and S4, injection molding and demolding. The system comprises the following modules: a module M1, an excimer laser module, a module M2, an LIGA process module, a module M3, an online detection module, a module M4 and a multi-material compatible module. According to the invention, the plasma density is inhibited to be below 1016cm <-3 > through a helium environment, the surface temperature gradient of the polymer substrate is synchronously reduced in combination with low-temperature cooling airflow, the width of a heat affected zone is compressed to 1.8 microns from 5 microns in a traditional process, and more than 80% of laser thermal stress is absorbed through a silicon dioxide buffer layer through a synergistic thermal response mechanism of a multi-layer photoresist structure. And interface stripping and microcracks are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-hole structure processing, and specifically provides a method and system for processing micro-hole structures by combining excimer laser and LIGA process. Background Art

[0002] In the field of micro-electromechanical systems, the demand for micro-hole structures with high aspect ratios and high precision is increasing. The traditional LIGA technology can prepare micro-structures with an aspect ratio exceeding 100 through deep X-ray lithography combined with electroforming process. However, it relies on synchrotron radiation light sources, resulting in huge equipment investment and long processing cycles, and it is difficult to meet the requirements of mass production. Although the quasi-LIGA technology (UV-LIGA) uses ultraviolet light instead of X-rays, significantly reducing the cost, it is limited by photoresist materials and optical diffraction effects, and it is difficult to achieve sub-micron feature sizes.

[0003] After retrieval, the patent with the Chinese patent number CN1063805C discloses a method for manufacturing multi-micro-hole hollow fibers by laser processing technology. The laser used is an excimer laser, with a wavelength range of 193nm to 248nm, and the laser energy intensity is 10mJ / cm to 500mJ / cm². The hollow fibers used should have a higher degree of orientation and a lower degree of crystallinity than ordinary fibers, with a crystallinity less than 25%, and the birefringence of the fiber body is greater than 0.18. The hollow fibers are irradiated with the excimer laser for 10 to 80 seconds, and a penetrative micro-hole structure is formed in the hollow fiber wall. Using this method, it is very convenient to punch micron-scale multi-micro-holes on the hollow fibers. The area of the multi-micro-holes can be arbitrarily selected axially or radially on the fiber, and it can be carried out either after fiber forming or after the fiber is made into a finished product, without chemical pollution.

[0004] The above patent uses a 193 - 248nm excimer laser to directly ablate fiber materials. Although micron-scale through-holes are achieved, there are two key defects. First, the control of the heat-affected zone is insufficient. The nanosecond pulse width of the excimer laser is prone to heat diffusion, which may cause carbonization or micro-cracks in polymer materials, and there is no mention of means to suppress thermal damage in the above technology. Second, the feature size is limited. Constrained by the ultraviolet diffraction limit (the theoretical resolution is about 100nm when the wavelength λ = 193nm) and the characteristics of photoresist materials, it is difficult for the finished product to break through the sub-micron processing accuracy. Based on this, the present invention designs a method and system for processing micro-hole structures by combining excimer laser and LIGA process to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for processing micro-hole structures by combining excimer laser and LIGA process, which solves the problem of insufficient control of the heat-affected zone in the background art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: A method and system for processing a micro-hole structure by combining an excimer laser and a LIGA process, comprising: Step S1, substrate pretreatment, sequentially coating a photosensitive resin layer on the surface of a metal substrate, where the bottom layer is a SU-8 thick resin with a thickness range of 50 to 200 microns, the intermediate dielectric layer is silicon dioxide, and the top layer is a PMMA thin resin with a thickness range of 1 to 5 microns, to form a multi-layer composite photoresist structure.

[0007] Step S2, excimer laser lithography, using a KrF excimer laser combined with a diffractive optical element mask for projection exposure, and by dynamically adjusting the laser scanning radius and energy density gradient, realizing a high aspect ratio micro-hole structure with controllable aperture taper.

[0008] Step S3, development and electroforming mold preparation, after developing with a tetramethylammonium hydroxide developer to form a three-dimensional photoresist mold, then electroforming in a nickel sulfamate electrolyte to fill the micro-hole structure and form a metal mold.

[0009] Step S4, injection molding and demolding, injecting polyether ether ketone into the metal mold using a high-temperature injection molding process, and after cooling, obtaining the micro-hole structure by ultrasonic vibration peeling.

[0010] Preferably, in step S2, a plasma shielding suppression technique is adopted, by applying a helium environment in the processing area to reduce the plasma shielding effect generated by the interaction between the ultraviolet laser and the material and improve the deep hole processing efficiency; the wavelength of the excimer laser is 248 nm, and by precisely controlling the pulse energy density and frequency, high-precision processing of the micro-hole structure is carried out.

[0011] Preferably, in step S3, a tetramethylammonium hydroxide developer is used for development, and the development time is optimized according to the photoresist thickness and exposure conditions to ensure the precise formation of the three-dimensional photoresist mold.

[0012] Preferably, in step S4, the temperature range of the high-temperature injection molding process is 350 - 400 °C, the injection pressure is 50 - 150 MPa, the holding pressure time is 5 - 15 seconds, and the cooling rate is 10 - 30 °C / s to ensure the integrity and dimensional accuracy of the micro-hole structure of polyether ether ketone; in the injection molding and demolding process, a silane-based demolding agent is used, and the coating thickness is 0.1 - 0.5 μm to ensure that the micro-hole structure is not damaged during the demolding process.

[0013] Preferably, the pressure of the helium environment is 0.5 - 2.0 bar, and the helium flow rate is 5 - 20 L / min to inhibit the plasma shielding effect and improve the deep hole processing efficiency.

[0014] Preferably, it includes the following modules: Module M1, an excimer laser module, integrating a KrF / ArF excimer laser, a beam homogenizer, and a dynamic focusing system. The dynamic focusing system uses an adaptive optical element and a Bessel beam generator to achieve microhole machining with a depth-to-diameter ratio greater than or equal to 100:1; Module M2, a LIGA process module, including an electroforming tank and an injection molding machine. The electroforming tank is equipped with a gradient pulse current system and a nano-diamond particle ultrasonic dispersion device; Module M3, an on-line detection module, integrating a femtosecond laser interferometer and a defect recognition model based on the U-Net architecture, for monitoring the three-dimensional morphology of microholes and dynamically adjusting laser parameters to suppress the heat-affected zone; Module M4, a multi-material compatibility module, equipped with a vacuum adsorption fixture and an infrared alignment system, for supporting the rapid switching and processing of metal substrates, ceramic substrates, and polymer substrates.

[0015] Preferably, the center wavelength of the Bessel beam generator is 248 nm, and the full width at half maximum is less than or equal to 1 μm. By reducing the optical diffraction effect through an annular light intensity distribution, it is used to break through the sub-micron precision limit of traditional ultraviolet lithography and achieve microhole machining with a pore diameter less than or equal to 500 nm; The beam homogenizer adopts a multi-prism array structure.

[0016] Preferably, the gradient pulse current system adopts a segmented regulation strategy, applying a high current density in the bottom area of the microhole to accelerate filling, and switching to a low current density in the orifice area to suppress edge burrs, so that the thickness error of the electroformed layer is less than or equal to ±1 μm; The nano-diamond particle ultrasonic dispersion device is equipped with an ultrasonic transducer with adjustable frequency to ensure uniform dispersion of particles.

[0017] Preferably, the on-line detection module integrates a plasma spectroscopy analysis unit to monitor the electron density distribution in the processing area in real time, and controls the pulse energy and scanning path of the excimer laser through feedback; The femtosecond laser interferometer has a sub-nanometer resolution, which is used to measure the three-dimensional morphology of microholes and provide data support for real-time adjustment of processing parameters.

[0018] Preferably, the vacuum adsorption fixture adopts a multi-layer micro-hole ceramic structure, and synchronously applies a low-temperature cooling air flow when processing polymer substrates to suppress the material carbonization problem caused by the thermal diffusion of excimer lasers; The infrared alignment system has a high-precision positioning ability, and the positioning accuracy is less than or equal to ±0.2 μm, which is used to ensure the rapid switching and precise alignment of different material substrates.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. In the present invention, the plasma density is suppressed to 10 16 cm -3Next, the temperature gradient on the surface of the polymer substrate is reduced synchronously with the low-temperature cooling airflow, and the width of the heat-affected zone is compressed from 5μm in the traditional process to 1.8μm. The synergistic thermal response mechanism of the multi-layer photoresist structure absorbs more than 80% of the laser thermal stress through the silicon dioxide buffer layer, avoiding interface delamination and microcracks.

[0020] 2. The present invention breaks through the diffraction limit of traditional ultraviolet lithography by adopting Bessel beam shaping technology. The annular light intensity distribution increases the energy density of the focal spot by 3 times. Combined with the dynamic focusing system, micro-hole processing with an aperture of ≤500 nm and an aspect ratio of ≥100:1 is achieved. The gradient photosensitivity of the three-layer photoresist guides the cross-scale transmission of laser energy, achieving a seamless transition from nanoscale surface morphology to micron-scale deep holes.

[0021] 3. The present invention uses a gradient pulse electroforming system combined with ultrasonic dispersion of nano-diamond particles to increase the Vickers hardness of the electroformed layer to 650 HV, the surface roughness Ra≤0.05μm, the thickness error≤±1μm, and supercritical CO2-assisted injection molding compensates for 0.3-0.5% shrinkage through microbubble nucleation, and cooperates with ultrasonic demolding to achieve a pore size tolerance of ±0.5μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the microporous structure processing method of the present invention; Figure 2 It is a module diagram of the microporous structure processing system of the present invention; Figure 3 It is a schematic diagram of the structure of the excimer laser module of the present invention; Figure 4 It is the working flow chart of the online detection module of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1; See also Figures 1-4, in the embodiments of the present invention, a method for processing a microporous structure by combining excimer laser and LIGA process includes: Step S1, substrate pretreatment, sequentially coating a photosensitive resin layer on the surface of a metal substrate, where the bottom layer is SU-8 thick resin with a thickness range of 50 to 200 microns, the intermediate dielectric layer is silicon dioxide, and the top layer is PMMA thin resin with a thickness range of 1 to 5 microns to form a multi-layer composite photoresist structure; Step S2, excimer laser lithography, using a KrF excimer laser combined with a diffractive optical element mask for projection exposure, and by dynamically adjusting the laser scanning radius and energy density gradient, a high aspect ratio microporous structure with controllable aperture taper is achieved; Step S3, development and electroforming mold preparation, after developing with a tetramethylammonium hydroxide developer to form a three-dimensional photoresist mold, then electroforming in a nickel sulfamate electrolyte to fill the microporous structure and form a metal mold; Step S4, injection molding and demolding, injecting polyetheretherketone into the metal mold using a high-temperature injection molding process, and after cooling, obtaining the microporous structure by ultrasonic vibration peeling.

[0025] In Step S2, a plasma shielding suppression technique is adopted. By applying a helium gas environment in the processing area, it is used to reduce the plasma shielding effect generated by the interaction between the ultraviolet laser and the material and improve the deep hole processing efficiency; the wavelength of the excimer laser is 248 nm, and by precisely controlling the pulse energy density and frequency, high-precision processing of the microporous structure is carried out. In Step S3, a tetramethylammonium hydroxide developer is used for development, and the development time is optimized according to the photoresist thickness and exposure conditions to ensure the precise formation of the three-dimensional photoresist mold. In Step S4, the temperature range of the high-temperature injection molding process is 350 - 400 °C, the injection pressure is 50 - 150 MPa, the holding pressure time is 5 - 15 seconds, and the cooling rate is 10 - 30 °C / s to ensure the integrity and dimensional accuracy of the microporous structure of polyetheretherketone; the release agent is a silane-based release agent with a coating thickness of 0.1 - 0.5 μm to ensure that the microporous structure is not damaged during demolding. The pressure of the helium gas environment is 0.5 - 2.0 bar, and the helium gas flow rate is 5 - 20 L / min to suppress the plasma shielding effect and improve the deep hole processing efficiency.

[0026] The working principle of the embodiments of the present invention is: the cooperative response mechanism of the multi-layer photoresist structure. The bottom layer SU-8 thick resin serves as the main support layer, and its epoxy groups undergo a cross-linking reaction after excimer laser exposure to form a three-dimensional network structure with high mechanical strength; the intermediate silicon dioxide layer serves as a stress buffer layer, and through its low thermal expansion coefficient characteristic, it inhibits the interfacial peeling between SU-8 and the metal substrate caused by the laser thermal effect; the top layer PMMA thin resin utilizes its high ultraviolet absorption rate characteristic to preferentially undergo chain scission degradation during KrF laser exposure to form an initial microporous guiding structure. The gradient photosensitive response characteristics of these three layers of structures achieve cross-scale control from nanoscale surface topography guidance to micron-scale deep hole forming.

[0027] The excimer laser spatio-temporal energy coupling technology divides the laser beam into a multi-focus array through wavefront modulation of the diffraction optical element mask, combines dynamic feedback adjustment of the scanning radius to form a spiral progressive exposure path in the X-Y plane, and at the same time, the laser energy density adopts a gradient attenuation mode, cooperating with the plasma suppression effect in a helium environment.

[0028] The cross-scale topography transfer of electroforming-injection molding: In the three-dimensional photoresist mold formed after development, nickel sulfamate electrolyte is electroformed in a pulse reverse current mode. The forward current density of 3 A / dm² realizes rapid filling at the bottom of the micro-holes, and the reverse current density of 0.5 A / dm² eliminates the tip effect, controlling the sidewall roughness of the metal mold within Ra < 0.2 μm. In the injection molding stage, polyether ether ketone is used for microcellular foaming molding assisted by supercritical CO2. When the melt temperature reaches 380 °C, the solubility of CO2 reaches 8 wt%. The sudden drop in pressure triggers cell nucleation. The micro-hole structure with a cell diameter ≤ 5 μm can compensate for the injection molding shrinkage rate, ensuring a dimensional accuracy of ±0.5 μm. The interface regulation of ultrasonic vibration peeling: During the demolding process, the silane-based demolding agent forms a self-assembled monolayer on the surface of the metal mold. The terminal amino group of it has a weak hydrogen bond interaction with the ketone group of PEEK. When 28 kHz ultrasonic vibration is applied, the interfacial shear stress concentration coefficient drops from 1.8 to 0.7, reducing the demolding critical pressure to 0.3 MPa.

[0029] Example 2; Please refer to Figures 1-4 , in the embodiment of the present invention, module M1, the excimer laser module, integrates a KrF / ArF excimer laser, a beam homogenizer and a dynamic focusing system. The dynamic focusing system uses an adaptive optical element and a Bessel beam generator to achieve micro-hole processing with a depth-to-diameter ratio greater than or equal to 100:1; module M2, the LIGA process module, includes an electroforming tank and an injection molding machine. The electroforming tank is equipped with a gradient pulse current system and a nano-diamond particle ultrasonic dispersion device; module M3, the on-line detection module, integrates a femtosecond laser interferometer and a defect recognition model based on the U-Net architecture, which is used to monitor the three-dimensional topography of the micro-holes and dynamically adjust the laser parameters to suppress the heat affected zone; module M4, the multi-material compatibility module, is equipped with a vacuum adsorption fixture and an infrared alignment system, which is used to support the rapid switching and processing of metal substrates, ceramic substrates and polymer substrates.

[0030] The central wavelength of the Bessel beam generator is 248 nm, and the full width at half maximum is less than or equal to 1 μm. It reduces the optical diffraction effect through the annular intensity distribution, is used to break through the sub-micron precision limit of traditional ultraviolet lithography, and realizes the micro-hole processing with an aperture less than or equal to 500 nm. The beam homogenizer adopts a multi-prism array structure. The gradient pulse current system adopts a segmented control strategy, applying a high current density in the bottom area of the micro-hole to accelerate filling, and switching to a low current density in the orifice area to suppress edge burrs, making the thickness error of the electroformed layer less than or equal to ±1 μm. The nano-diamond particle ultrasonic dispersion device is equipped with an ultrasonic transducer with adjustable frequency to ensure uniform dispersion of the particles. The on-line detection module integrates a plasma spectroscopy analysis unit to monitor the electron density distribution in the processing area in real time, and controls the pulse energy and scanning path of the excimer laser through feedback. The femtosecond laser interferometer has a sub-nanometer resolution, is used to measure the three-dimensional morphology of the micro-hole and provides data support for real-time adjustment of the processing parameters. The vacuum adsorption fixture adopts a multi-layer micro-hole ceramic structure, and synchronously applies a low-temperature cooling air flow when processing the polymer substrate to suppress the carbonization problem of the material caused by the thermal diffusion of the excimer laser. The infrared alignment system has a high-precision positioning ability, and the positioning accuracy is less than or equal to ±0.2 μm, which is used to ensure the rapid switching and precise alignment of different material substrates.

[0031] The working principle of the embodiment of the present invention is as follows: The deep sub-micron processing mechanism of the excimer laser module uses a Bessel beam generator to break through the diffraction limit of the traditional Gaussian beam, forms a high-energy flux density area without diffraction effect through the annular intensity distribution, and the multi-prism array beam homogenizer realizes an intensity uniformity of ±2%, and cooperates with the adaptive optical element to dynamically compensate the thermal lens effect. When the laser pulse acts on the substrate, the ArF excimer laser breaks the material molecular bond through the photochemical ablation mechanism, and combines with the dynamic focusing system to realize the micro-hole processing with a depth-to-diameter ratio ≥100:1.

[0032] The multi-physical field coupling control of the LIGA process module uses a gradient pulse current system in the electroforming tank to form a local turbulence effect at the bottom of the micro-hole, and the nickel ion migration rate is increased to 2.3 times that of the conventional process; the orifice area is switched to a low current density mode to suppress dendrite growth through electrochemical polarization. The nano-diamond particles form a stable suspension with a Zeta potential ≥35 mV under the action of the ultrasonic dispersion device, making the Vickers hardness of the electroformed layer increase to 650 HV and the surface roughness Ra ≤0.05 μm.

[0033] The real-time closed-loop control of the on-line detection module. The femtosecond laser interferometer reconstructs the three-dimensional morphology of the micro-hole through the phase-shifting interference method, combines with the U-Net convolutional neural network to realize the real-time recognition of the hole wall taper and aperture deviation, and the plasma spectroscopy analysis unit inversely calculates the electron temperature and density distribution through the Stark broadening effect, and dynamically adjusts the laser pulse energy and scanning path to compensate for the deformation of the heat-affected zone.

[0034] Thermo-mechanical collaborative management of multi-material compatible modules. The vacuum adsorption fixture adopts a multi-layer microporous ceramic structure. When processing polymer substrates, nitrogen gas at -30°C is introduced synchronously, reducing the surface temperature gradient of the material to 15°C / mm and reducing the carbonized area by 78%. The infrared alignment system achieves a positioning accuracy of ±0.2μm through dual-frequency interference ranging. Combining with the Hough transform recognition algorithm for substrate feature points, the switching alignment time for metal / ceramic / polymer substrates is ≤3s.

[0035] Example 3; Please refer to Figures 1-4 , a specific embodiment of the machining of airfoil cooling holes in an aero-engine is provided. Substrate pretreatment Select 316L stainless steel as the metal substrate. After removing surface oxides by ultrasonic cleaning (frequency 40 kHz, time 10 minutes), three layers of photosensitive glue are coated in sequence: Bottom layer SU-8 thick glue: The thickness is 120 microns. The spin-coating process (rotation speed 800 rpm, time 30 seconds) is used, and the pre-baking conditions are 95°C and 5 minutes; Intermediate dielectric layer silicon dioxide: Prepared by plasma-enhanced chemical vapor deposition (PECVD), with a thickness of 2 microns and a dielectric constant of 3.9; Top layer PMMA thin glue: The thickness is 3 microns. The spin-coating process (rotation speed 3000 rpm, time 60 seconds) is used, and the soft-baking conditions are 180°C and 2 minutes.

[0036] Excimer laser lithography

[0037] Use a KrF excimer laser (wavelength 248 nm, pulse energy density 200 mJ / cm², repetition frequency 50 Hz), and perform projection exposure with a diffractive optical element (DOE) mask. Dynamically adjust the laser scanning radius to 2.5 mm, and the energy density gradient change rate is 15 mJ / cm²·μm. Combine with a helium environment (pressure 1.2 bar, flow rate 12 L / min) to suppress the plasma shielding effect. After the beam is shaped by Bessel (full width at half maximum 0.8 μm), a conical microporous structure with a pore diameter of 30 μm and an aspect ratio of 80:1 is formed on the photoresist.

[0038] Development and electroforming mold preparation

[0039] Use a tetramethylammonium hydroxide developer (concentration 2.38%) for development for 8 minutes to form a three-dimensional photoresist mold. Subsequently, gradient pulse electroforming is carried out in a nickel sulfamate electrolyte (nickel ion concentration 80 g / L, pH 4.0, temperature 50°C). Diamond particles with a particle size of 50 nm (concentration 1.2 vol%) are added to the electrolyte, and ultrasonic dispersion (power 500 W, frequency 40 kHz) is used to ensure uniform distribution. Finally, a nickel mold with a surface hardness of HV620 is prepared.

[0040] Injection Molding and Demolding

[0041] The polyetheretherketone (PEEK) particles are heated to 380 °C and melted in an injection molding machine, injected into a metal mold at a pressure of 100 MPa, and cooled to 120 °C at a rate of 20 °C / s after holding the pressure for 10 seconds. Before demolding, a silane-based demolding agent (thickness 0.3 μm) is sprayed on the mold surface, and non-destructive separation is achieved through ultrasonic vibration (frequency 28 kHz, amplitude 15 μm) to obtain a microporous structure with a pore size tolerance of ±1.5 μm and a taper of 0.3°.

[0042] System Operating Parameters

[0043] Excimer Laser Module: The Bessel beam generator of the excimer laser module outputs a wavelength of 248 nm, with an annular light intensity distribution and a focal full width at half maximum of 0.8 μm; the dynamic focusing system uses an adaptive deformable mirror (response time 0.8 ms), and the Z-axis positioning accuracy is ±0.1 μm.

[0044] Online Detection Module: A femtosecond laser interferometer (wavelength 800 nm, resolution 0.1 nm) scans the three-dimensional morphology of the micropores in real time; a defect recognition model based on the U-Net architecture (the training data set contains 100,000 groups of micropore images), and the recognition threshold is set as burr ≤ 0.5 μm and heat-affected zone width ≤ 1.8 μm.

[0045] Multi-Material Compatibility Module: The vacuum adsorption fixture adopts a multi-layer microporous ceramic structure (pore size 10 μm), and nitrogen gas at -10 °C (flow rate 8 L / min) is introduced synchronously when processing the PEEK substrate; the positioning accuracy of the infrared alignment system is ±0.15 μm, and the switching time between 316L stainless steel, alumina ceramic, and PEEK substrate is ≤ 3 minutes.

[0046] The working principle of the embodiment of the present invention is as follows: Through Bessel beam shaping and plasma shielding technology, micropores with a pore size of 30 μm and an aspect ratio of 80:1 are processed, and the sidewall perpendicularity reaches 89°, breaking through the diffraction limit of traditional ultraviolet lithography; the synergistic effect of the helium environment and low-temperature air flow reduces the heat-affected zone width from 5 μm in the traditional process to 1.8 μm, avoiding carbonization of polymer materials; gradient pulse electroforming and nano-diamond strengthening enable the mold life to reach 120,000 injection molding cycles, and the pore size deviation is controlled within ±2%.

[0047] Working principle: The excimer laser module uses Bessel beam shaping and plasma shielding technologies to break through the diffraction limit of traditional ultraviolet lithography and achieve micro-hole processing with a pore diameter less than 500 nm and an aspect ratio greater than 100:1. The bottom SU-8 thick film serves as the main support layer, and its epoxy groups undergo a cross-linking reaction after laser exposure to form a three-dimensional network structure with high mechanical strength; the middle silica layer serves as a stress buffer layer to inhibit interface peeling caused by the laser thermal effect; the top PMMA thin film uses its high ultraviolet absorption rate characteristic to preferentially undergo chain-breaking degradation to form an initial micro-hole guiding structure. By suppressing the plasma shielding effect in a helium environment and combining with dynamically adjusting the laser scanning radius and energy density gradient, the verticality of the micro-hole sidewall reaches 89°, and the width of the heat-affected zone is reduced from 5 μm in the traditional process to 1.8 μm.

[0048] The LIGA process module is strengthened by a gradient pulse current system and nano-diamond particles, achieving an electroformed layer thickness error of less than ±1 μm, a Vickers hardness increased to 650 HV, and a surface roughness Ra ≤ 0.05 μm. In the three-dimensional photoresist mold formed after development, nickel sulfamate electrolyte is electroformed in a pulsed reverse current mode. A forward current density of 3 A / dm² enables rapid filling at the bottom of the micro-hole, and a reverse current density of 0.5 A / dm² eliminates the tip effect, ensuring that the sidewall roughness of the metal mold is controlled at Ra < 0.2 μm. In the injection molding stage, polyether ether ketone is used for micro-foaming molding assisted by supercritical CO2. The micro-hole structure with a pore diameter ≤ 5 μm can compensate for the injection molding shrinkage rate, ensuring a dimensional accuracy of ±0.5 μm.

[0049] The on-line detection module uses a femtosecond laser interferometer and a defect recognition model based on the U-Net architecture to monitor the three-dimensional morphology of the micro-holes in real time and dynamically adjust the laser parameters to suppress the heat-affected zone. The plasma spectroscopy analysis unit inversely calculates the electron temperature and density distribution through the Stark broadening effect, and dynamically adjusts the laser pulse energy and scanning path to compensate for the deformation of the heat-affected zone, ensuring the processing accuracy.

[0050] The multi-material compatibility module, through the synergistic effect of a vacuum adsorption fixture and an infrared alignment system, supports the rapid switching and precise alignment of metal, ceramic, and polymer substrates. The vacuum adsorption fixture uses a multi-layer micro-hole ceramic structure, and a low-temperature cooling air flow is synchronously applied during the processing of polymer substrates to inhibit the carbonization problem of the material caused by the thermal diffusion of the excimer laser; the infrared alignment system achieves a positioning accuracy of ±0.2 μm through dual-frequency interference ranging, and combines with the Hough transform recognition algorithm for substrate feature points to complete the material substrate switching and alignment time ≤ 3 seconds.

[0051] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for processing a microporous structure by combining an excimer laser with the LIGA process, characterized in that, Including: Step S1, substrate pretreatment, sequentially coating a photosensitive adhesive layer on the surface of a metal substrate, where the bottom layer is SU-8 thick glue with a thickness range of 50 to 200 microns, the intermediate dielectric layer is silicon dioxide, and the top layer is PMMA thin glue with a thickness range of 1 to 5 microns, to form a multi-layer composite photoresist structure; Step S2, excimer laser lithography, using a KrF excimer laser combined with a diffractive optical element mask for projection exposure, and realizing a high aspect ratio micro-hole structure with controllable aperture taper by dynamically adjusting the laser scanning radius and energy density gradient; Step S3, development and electroforming mold preparation, forming a three-dimensional photoresist mold after development with a tetramethylammonium hydroxide developer, and then performing electroforming in a nickel sulfamate electrolyte to fill the micro-hole structure and form a metal mold; Step S4, injection molding and demolding, injecting polyetheretherketone into the metal mold by a high-temperature injection molding process, and obtaining the micro-hole structure by ultrasonic vibration peeling after cooling.

2. The method for processing a microporous structure by combining an excimer laser and a LIGA process according to claim 1, wherein, In the step S2, a plasma shielding suppression technology is adopted, and a helium environment is applied in the processing area to reduce the plasma shielding effect generated by the interaction between ultraviolet laser and materials and improve the deep-hole processing efficiency; the wavelength of the excimer laser is 248 nm, and high-precision processing of the micro-hole structure is carried out by precisely controlling the pulse energy density and frequency.

3. A method for processing a micro-hole structure by combining excimer laser and LIGA process according to claim 1, characterized in that: In the step S3, a tetramethylammonium hydroxide developer is used for development, and the development time is optimized according to the photoresist thickness and exposure conditions to ensure the precise formation of the three-dimensional photoresist mold.

4. A method for machining a microhole structure by combining an excimer laser and a LIGA process according to claim 1, characterized in that: In the step S4, the temperature range of the high-temperature injection molding process is 350 - 400 °C, the injection pressure is 50 - 150 MPa, the holding pressure time is 5 - 15 seconds, and the cooling rate is 10 - 30 °C / s to ensure the integrity and dimensional accuracy of the micro-hole structure of polyetheretherketone; in the injection molding and demolding, a silane-based mold release agent is used, and the coating thickness is 0.1 - 0.5 μm to ensure that the micro-hole structure is not damaged during the demolding process.

5. A method for processing a microporous structure by combining an excimer laser and a LIGA process according to claim 2, characterized in that: The pressure of the helium environment is 0.5 - 2.0 bar, and the helium flow rate is 5 - 20 L / min to suppress the plasma shielding effect and improve the deep-hole processing efficiency.

6. A micro-hole structure processing system combining an excimer laser and LIGA technology, characterized in that: Including the following modules: Module M1, excimer laser module, integrating a KrF / ArF excimer laser, a beam homogenizer and a dynamic focusing system, and the dynamic focusing system adopts an adaptive optical element and a Bessel beam generator to realize micro-hole processing with a depth-to-diameter ratio greater than or equal to 100:1; Module M2, LIGA process module, including an electroforming tank and an injection molding machine, and the electroforming tank is configured with a gradient pulse current system and a nano-diamond particle ultrasonic dispersion device; Module M3, on-line detection module, integrating a femtosecond laser interferometer and a defect recognition model based on the U-Net architecture, for monitoring the three-dimensional morphology of micro-holes and dynamically adjusting laser parameters to suppress the heat-affected zone; Module M4, multi-material compatibility module, configured with a vacuum adsorption fixture and an infrared alignment system, for supporting the rapid switching and processing of metal substrates, ceramic substrates and polymer substrates.

7. A microhole structure processing system combining excimer laser and LIGA process according to claim 6, characterized in that, The central wavelength of the Bessel beam generator is 248 nm, and the full width at half maximum is less than or equal to 1 μm. It reduces the optical diffraction effect through the annular light intensity distribution, and is used to break through the sub-micron precision limit of traditional ultraviolet lithography to achieve micro-hole processing with a pore diameter less than or equal to 500 nm. The beam homogenizer adopts a multi-prism array structure.

8. A micro-hole structure processing system combining excimer laser and LIGA process according to claim 6, characterized in that, The gradient pulse current system adopts a segmented regulation strategy, applying a high current density in the bottom area of the micro-hole to accelerate filling, and switching to a low current density in the orifice area to suppress edge burrs, making the electroformed layer thickness error less than or equal to ±1 μm. The nano-diamond particle ultrasonic dispersion device is equipped with an ultrasonic transducer with adjustable frequency to ensure uniform dispersion of the particles.

9. The micro-hole structure processing system combining excimer laser and LIGA process according to claim 6, characterized in that, The on-line detection module integrates a plasma spectral analysis unit to monitor the electron density distribution in the processing area in real time, and controls the pulse energy and scanning path of the excimer laser through feedback. The femtosecond laser interferometer has a sub-nanometer resolution, which is used to measure the three-dimensional morphology of the micro-hole and provide data support for real-time adjustment of processing parameters.

10. A micro-hole structure processing system combining excimer laser and LIGA process according to claim 6, characterized in that, The vacuum adsorption fixture adopts a multi-layer micro-hole ceramic structure, and synchronously applies a low-temperature cooling air flow when processing polymer substrates to suppress the material carbonization problem caused by the thermal diffusion of the excimer laser. The infrared alignment system has a high-precision positioning ability, and the positioning accuracy is less than or equal to ±0.2 μm, which is used to ensure the rapid switching and precise alignment of different material substrates.

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