A method for fabricating a flexible array microprobe

Abstract

The application discloses a preparation method of a flexible array microprobe in the field of semiconductors and microelectronics, and comprises the following steps: step S1, providing a quartz glass substrate, performing organic cleaning treatment, the cleaning process comprising three-step ultrasonic cleaning of acetone-isopropyl alcohol-deionized water, ultrasonic power being 50-200 W, time being 5-15 minutes, and drying in a 80 DEG C vacuum oven for 30 minutes after cleaning; step S2, preparing an ultraviolet narrow-band filter film on the quartz glass substrate, and the filter film adopting an HfO2 / SiO2 alternating film layer structure. The application designs an ultraviolet narrow-band filter for a wide-spectrum photoetching machine (mercury lamp spectrum range 300-600 nm) exposure light source, realizes specific wavelength selective transmission, improves diffraction light field definition of the narrow-band filter, and improves micro-needle sidewall smoothness; moreover, without complex mask exposure equipment or gray-scale mask plate preparation, through ultraviolet narrow-band filter design and diffraction light field regulation technology, the process flow is simplified, micro-needle geometric precision is improved, and process cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductors and microelectronics, specifically a method for fabricating flexible array microprobes. Background Technology

[0002] In recent years, flexible array microprobes have been widely used in biomedicine (such as drug delivery and skin puncture) and sensors (such as flexible electronic tactile sensors and biosensors). Currently, the mainstream fabrication technologies for array microprobes include various micro-nano fabrication techniques such as microtemplation (casting, hot embossing, and injection molding), 3D printing, MEMS micromachining, laser ablation, and LIGA processes.

[0003] Microtemplating is a commonly used method for preparing polymer array microneedles, mainly including casting, thermoforming, and injection molding. These methods use microtemplates to precisely control the geometry of the microneedles. Polydimethylsiloxane (PDMS) is the most commonly used template material due to its softness and non-adhesion to polymer materials. Casting involves casting a mixture of drug and polymer onto a microneedle array mold, filling the solution using centrifugation, vacuuming, or ultrasonication, and then drying to obtain the polymer array microneedles. However, casting may result in incomplete solution filling, leading to incomplete microneedle structures, and the drying process can be lengthy. Thermoforming involves heating the polymer material to a certain temperature to fully fill the mold, then cooling and solidifying before demolding. However, thermoforming requires high temperature control; unsuitable temperatures may alter the polymer material properties or prevent proper mold filling, and the demolding process may damage the microneedle structure. Injection molding uses an injection molding machine to pressurize molten polymer, filling it into a mold, and then cooling to form microneedles. However, injection molding requires high-precision injection equipment, which is costly, and improper injection pressure control can lead to deviations in the microneedle shape. 3D printing technology can manufacture microneedles with complex geometries. This method achieves microneedle customization through layer-by-layer material deposition and is suitable for manufacturing microneedles with features such as drug reservoirs or drug delivery channels. Although 3D printing allows for customized microneedle geometry, it currently faces limitations in resolution and speed. The accuracy of the printed microneedles may not meet the requirements of some high-precision applications, and the relatively slow printing speed makes it unsuitable for large-scale production. Furthermore, some materials may not be suitable for biomedical applications, limiting its widespread use in the biomedical field, and 3D printing equipment is typically expensive and has high maintenance costs. MEMS micromachining is widely used in the fabrication of microneedle arrays. This technology can provide high-precision patterning and is suitable for manufacturing complex microneedle arrays. By patterning a polymer film using a photomask and then etching to create a microneedle array, photolithography enables precise control of the microneedle geometry. Combining dry and wet etching techniques can produce microneedle arrays with high aspect ratios. Sacrificial layer technology can sharpen the tips of microneedles during etching, thereby improving their strength and performance. However, photolithography can be time-consuming and requires expensive equipment, is complex, and demands high operator skill. Dry etching typically requires a vacuum environment, involving complex and costly equipment, and is difficult to operate. Wet etching can lead to sidewall tilting due to isotropic etching, affecting the geometric accuracy of the microneedles. Furthermore, the etching solution is corrosive, requiring strict control of etching time and conditions to avoid over-etching or under-etching. Proper disposal of etching waste is also essential to prevent environmental pollution. Laser ablation technology focuses a laser beam onto the material surface, causing localized melting and vaporization, thus forming microneedle structures.This method allows for precise control of the microneedle geometry, making it suitable for manufacturing microneedles with high aspect ratios. However, laser ablation technology is also expensive and requires specialized equipment, resulting in high purchase and maintenance costs. Furthermore, the laser ablation process can cause thermal damage to the material, affecting the performance and quality of the microneedles. Precise control of laser parameters is crucial during operation; otherwise, processing defects such as rough surfaces and irregular shapes can easily occur. LIGA technology involves steps such as X-ray lithography, electroforming, and plastic casting. This method can produce microneedles with high strength and precise dimensions, suitable for transdermal drug delivery systems. However, LIGA technology is complex, involving multiple high-precision processing steps, each requiring strict condition control, placing extremely high demands on equipment and technology, leading to very high production costs. Moreover, the entire fabrication process is time-consuming, making it unsuitable for large-scale rapid production. UV-LIGA technology, by using ultraviolet lithography instead of traditional X-ray lithography, reduces costs and simplifies the process flow, and combined with micro-nano technology, has had a positive impact on microprobe fabrication. However, its resolution and aspect ratio are generally lower than traditional LIGA technology. This limits its application in the fabrication of microprobes that require extremely high precision and aspect ratio.

[0004] Existing methods generally suffer from the following drawbacks: high process complexity, requiring precise control of multiple steps (such as temperature, pressure, and etching conditions); high cost, relying on high-precision equipment (such as injection molding machines, lithography machines, and vacuum etching equipment); limited production scale, with low efficiency of 3D printing and LIGA technologies, making mass production difficult; and insufficient precision, with casting methods prone to structural defects and wet etching causing sidewall tilting.

[0005] Therefore, those skilled in the art provide a method for preparing flexible array microprobes to solve the problems mentioned in the background art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing flexible array microprobes to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for fabricating a flexible array microprobe includes the following steps:

[0009] Step S1: Provide a quartz glass substrate and perform organic cleaning treatment. The cleaning process includes three-step ultrasonic cleaning of acetone, isopropanol and deionized water. The ultrasonic power is 50-200W and the time is 5-15 minutes. After cleaning, dry in a vacuum oven at 80℃ for 30 minutes.

[0010] Step S2: Prepare a narrow-band UV filter film on a quartz glass substrate. The filter film adopts an alternating HfO2 / SiO2 film layer structure, and the film layer design meets the following transmittance requirements:

[0011] T(λ)≥80% (within the target band);

[0012] And the out-of-band suppression ratio is ≥30dB;

[0013] Step S3: A Cr / CrOx composite metal film is deposited on the other side of the filter film by magnetron sputtering, followed by photolithography and reactive ion etching (RIE) to form a micron-scale array of circular holes. The etching selectivity meets the following requirements:

[0014]

[0015] Where: R Cr R is the Cr etching rate. PR The photoresist etching rate;

[0016] Step S4, in Cr / CrO x Positive photoresist is spin-coated onto the film layer, and a micron-scale array of circular holes is formed by photolithography and dry etching. The etching parameters are: etching gas Cl2:O2:Ar=40:8:10sccm, RF power 150W, vacuum degree 20mTorr; the resulting circular holes have a diameter of 5-50μm, a period of 10-200μm, and an aspect ratio ≥5:1.

[0017] Step S5: Coat the etched Cr film with UV adhesive and expose it for curing as a probe substrate. Coating parameters: Use SU-8 2000 series or Loctite 3526 UV adhesive; spin coating speed 500-3000 rpm; adhesive layer thickness 50-200 μm; thickness uniformity within ±3%.

[0018] Step S6: Perform plasma activation treatment on the UV film layer. Treatment parameters: O2 / Ar mixed gas ratio 1:3, power 100-300W, gas pressure 10-50Pa, time 5-10 minutes.

[0019] Step S7: Coat the activated surface with negative photoresist SU-8 2010, and expose it through a Bessel diffraction light field generated by a micro-aperture array. The light intensity distribution I(r,z) approximates the Bessel function. Where J0 is the zeroth-order Bessel function and α is the light absorption coefficient.

[0020] Step S8: After development, a high aspect ratio flexible array of microneedles is formed. Development parameters: the developer is propylene glycol methyl ether acetate, and the development time is 2–10 minutes; the resulting microneedle cone angle θ satisfies: ΔI is the radial light intensity change rate;

[0021] Step S9: Separate the film layer to obtain the final flexible array microneedle structure.

[0022] As a further aspect of the present invention: the film structure of the ultraviolet narrowband filter film in step S2 is any one of the following:

[0023] a) For the 360-370nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H(LH)^4|Substruct" is adopted, with a film thickness of:

[0024] Substruct|HfO2(44.98nm) / SiO2(63.54nm) / ... / SiO2(118.79nm)|Air;

[0025] b) For the 400-410nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H(LH)^4|Substruct" is adopted, with a film thickness of:

[0026] Substruct|HfO2(36.28nm) / SiO2(63.04nm) / ... / SiO2(49.53nm)|Air;

[0027] c) For the 430-440nm wavelength band, a 26-layer structure of "Air|LH···LH|Substruct" is adopted, with a film thickness of:

[0028] Substruct|HfO2(27.44nm) / SiO2(64.63nm) / ... / SiO2(127.70nm)|Air.

[0029] As a further aspect of the present invention: the optical characteristics of the micro-aperture array in step S7 satisfy the following relationship between the aperture d and the exposure wavelength λ: Where NA is the numerical aperture of 0.3 to 0.6; the aperture period p satisfies: p ≥ d + 2δ, where δ is the light field diffusion distance of 1 μm.

[0030] As a further aspect of the present invention: the curing process of the UV adhesive in step S5 satisfies a kinetic model: Where C is the degree of crosslinking, k0 is the pre-exponential factor, and E a η is the activation energy, I is the light intensity, and m / n is the reaction order.

[0031] As a further aspect of the present invention: the exposure dose D of the negative photoresist in step S7 satisfies: Where D0 is the surface dose of 100–500 mJ / cm². 2 L p This represents the depth through which light penetrates.

[0032] As a further aspect of the present invention: the ion density n of the plasma activation treatment in step S6 i satisfy: n e For electron density, T e The electron temperature is 2–5 eV.

[0033] As a further aspect of the present invention, the microneedles in step S8 have the following characteristics:

[0034] 1) Aspect ratio ≥ 5:1;

[0035] 2) The elastic modulus E satisfies: Where E0 is the bulk material modulus, and t / L is the thickness-to-length ratio;

[0036] 3) Fracture toughness K_IC≥0.8MPa·m^1 / 2.

[0037] As a further embodiment of the present invention: in step S3, the thickness of the CrOx transition layer is 10–30 nm, the deposition parameters are: Ar:O2 = 3:1, total flow rate ≤ 40 sccm, and vacuum degree 1.0 × 10⁻⁶. -3 ~5×10 -1 Pa; Cr layer thickness 20–190 nm, deposition parameters: argon flow rate 10–50 sccm, vacuum degree 0.4–0.8 Pa.

[0038] As a further aspect of the present invention: in step S2:

[0039] For the 360-370nm band: average transmittance ≥80.5%, peak transmittance ≥99.998%@365.38nm;

[0040] For the 400-410nm band: average transmittance ≥85.2%, peak transmittance ≥99.89%@404.85nm;

[0041] For the 430-440nm band: average transmittance ≥65.5%, peak transmittance ≥99.90%@435.94nm.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] 1. Single-wavelength light field sharpening: A UV narrow-band filter was designed for the exposure light source of a broadband lithography machine (mercury lamp spectral range 300-600nm), which achieves selective transmission of specific wavelengths. The narrow-band filter improves the clarity of the diffraction light field and improves the smoothness of the microneedle sidewalls.

[0044] 2. Simplified process: This technical solution does not require complex mask exposure equipment or grayscale mask preparation. By using ultraviolet narrowband filter design and diffraction field modulation technology, the process flow is simplified and the geometric accuracy of microneedles is improved, thus reducing process costs. 3. Mass production: It is suitable for the manufacture of large-area flexible array microprobes. Attached Figure Description

[0045] Figure 1 This is the mercury lamp spectrum of the broadband lithography machine in this invention;

[0046] Figure 2 This is a transmission curve of the JGS1 quartz glass in this invention;

[0047] Figure 3 This is a diffraction field distribution diagram of a 365nm beam passing through a 4µm aperture in this invention;

[0048] Figure 4 This is a schematic diagram of the fabrication process of the flexible array microprobe in this invention;

[0049] Figure 5 This is a transmittance curve of the 360nm-370nm ultraviolet filter in this invention.

[0050] Figure 6 This is a transmittance curve of the 400nm-410nm ultraviolet filter in this invention.

[0051] Figure 7 This is a transmittance curve of the 430nm-440nm ultraviolet filter in this invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] like Figure 1-4 As shown, a method for fabricating a flexible array microprobe includes the following steps:

[0054] Step S1: Provide a quartz glass substrate and perform organic cleaning treatment. The cleaning process includes three-step ultrasonic cleaning of acetone, isopropanol and deionized water. The ultrasonic power is 50-200W and the time is 5-15 minutes. After cleaning, dry in a vacuum oven at 80℃ for 30 minutes.

[0055] Step S2: Prepare a narrow-band UV filter film on a quartz glass substrate. The filter film adopts an alternating HfO2 / SiO2 film layer structure, and the film layer design meets the following transmittance requirements:

[0056] T(λ)≥80% (within the target band);

[0057] And the out-of-band suppression ratio is ≥30dB;

[0058] Step S3: A Cr / CrOx composite metal film is deposited on the other side of the filter film by magnetron sputtering, followed by photolithography and reactive ion etching (RIE) to form a micron-scale array of circular holes. The etching selectivity meets the following requirements:

[0059]

[0060] Where: R Cr R is the Cr etching rate. PR The photoresist etching rate;

[0061] Step S4, in Cr / CrO x Positive photoresist is spin-coated onto the film layer, and a micron-scale array of circular holes is formed by photolithography and dry etching. The etching parameters are: etching gas Cl2:O2:Ar=40:8:10sccm, RF power 150W, vacuum degree 20mTorr; the resulting circular holes have a diameter of 5-50μm, a period of 10-200μm, and an aspect ratio ≥5:1.

[0062] Step S5: Coat the etched Cr film with UV adhesive and expose it for curing as a probe substrate. Coating parameters: Use SU-8 2000 series or Loctite 3526 UV adhesive; spin coating speed 500-3000 rpm; adhesive layer thickness 50-200 μm; thickness uniformity within ±3%.

[0063] Step S6: Perform plasma activation treatment on the UV film layer. Treatment parameters: O2 / Ar mixed gas ratio 1:3, power 100-300W, gas pressure 10-50Pa, time 5-10 minutes.

[0064] Step S7: Coat the activated surface with negative photoresist SU-8 2010, and expose it through a Bessel diffraction light field generated by a micro-aperture array. The light intensity distribution I(r,z) approximates the Bessel function. Where J0 is the zeroth-order Bessel function and α is the light absorption coefficient.

[0065] Step S8: After development, a high aspect ratio flexible array of microneedles is formed. Development parameters: the developer is propylene glycol methyl ether acetate, and the development time is 2–10 minutes; the resulting microneedle cone angle θ satisfies: ΔI is the radial light intensity change rate;

[0066] Step S9: Separate the film layer to obtain the final flexible array microneedle structure.

[0067] By adopting the above technical solution, steps 1, 4, and 7, through the integrated process of "ultraviolet narrowband filter + Bessel light field exposure," simplify the traditional 5-7 step photolithography process of MEMS into 3 core steps. An ultraviolet narrowband filter was designed for the exposure light source of a broadband photolithography machine (mercury lamp spectral range 300-600nm), achieving selective transmission of specific wavelengths. The narrowband filter improves the clarity of the diffraction light field and enhances the smoothness of the microneedle sidewalls. Furthermore, it eliminates the need for complex mask exposure equipment or grayscale mask preparation. Through the design of the ultraviolet narrowband filter and the diffraction light field modulation technology, the process flow is simplified, the geometric accuracy of the microneedles is improved, and the process cost is reduced. This method is suitable for the fabrication of large-area flexible array microprobes.

[0068] The film structure of the ultraviolet narrowband filter in step S2 is any one of the following:

[0069] a) For the 360-370nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H(LH)^4|Substruct" is adopted, with a film thickness of:

[0070] Substruct|HfO2(44.98nm) / SiO2(63.54nm) / ... / SiO2(118.79nm)|Air;

[0071] b) For the 400-410nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H(LH)^4|Substruct" is adopted, with a film thickness of:

[0072] Substruct|HfO2(36.28nm) / SiO2(63.04nm) / ... / SiO2(49.53nm)|Air;

[0073] c) For the 430-440nm wavelength band, a 26-layer structure of "Air|LH···LH|Substruct" is adopted, with a film thickness of:

[0074] Substruct|HfO2(27.44nm) / SiO2(64.63nm) / ... / SiO2(127.70nm)|Air.

[0075] In step S7, the optical characteristics of the micro-aperture array satisfy the following relationship: the aperture d and the exposure wavelength λ are: Where NA is the numerical aperture of 0.3 to 0.6; the aperture period p satisfies: p ≥ d + 2δ, where δ is the light field diffusion distance of 1 μm.

[0076] In step S5, the curing process of the UV adhesive satisfies a kinetic model: Where C is the degree of crosslinking, k0 is the pre-exponential factor, and E a I represents the activation energy, I represents the light intensity, and m / n represents the reaction order, enabling automated control of process parameters and reducing human intervention.

[0077] In step S7, the exposure dose D of the negative photoresist satisfies: Where D0 is the surface dose of 100–500 mJ / cm². 2 L p This represents the depth through which light penetrates.

[0078] In step S6, the ion density n of the plasma activation treatment i satisfy: n e For electron density, T e The electron temperature is 2–5 eV.

[0079] The microneedles in step S8 have the following characteristics:

[0080] 1) Aspect ratio ≥ 5:1;

[0081] 2) The elastic modulus E satisfies: Where E0 is the bulk material modulus, and t / L is the thickness-to-length ratio;

[0082] 4) Fracture toughness K_IC≥0.8MPa·m^1 / 2.

[0083] In step S3, the CrOx transition layer thickness is 10–30 nm, the deposition parameters are: Ar:O2 = 3:1, total flow rate ≤ 40 sccm, and vacuum degree 1.0 × 10⁻⁶. -3 ~5×10 -1 Pa; Cr layer thickness 20–190 nm, deposition parameters: argon flow rate 10–50 sccm, vacuum degree 0.4–0.8 Pa.

[0084] In step S2:

[0085] For the 360-370nm band: average transmittance ≥80.5%, peak transmittance ≥99.998%@365.38nm;

[0086] For the 400-410nm band: average transmittance ≥85.2%, peak transmittance ≥99.89%@404.85nm;

[0087] For the 430-440nm wavelength band: average transmittance ≥ 65.5%, peak transmittance ≥ 99.90% @ 435.94nm

[0088] Example 1: Standard microneedle array in the 360-370nm band

[0089] like Figure 4 The diagram shows a fabrication process flow for a flexible array microprobe. Embodiment 1 of this invention provides a method for fabricating a flexible array probe. The mercury lamp exposure light source in a broadband lithography machine is mainly concentrated in the wavelength range of 350nm to 450nm. In Embodiment 1, a 360-370nm (i-line) ultraviolet narrowband filter is first designed on one side of a quartz glass plate. Then, Cr metal micropores are designed on the other side of the glass plate to control the light field distribution. Finally, an ultraviolet resist is coated onto the Cr film as the probe substrate. After coating with ultraviolet negative photoresist SU-8 2010 and exposure and development, a flexible array microprobe is formed. The specific steps are as follows:

[0090] Step 1, Organic Cleaning: Clean the JGS1 quartz glass plate. First, pretreat the sample with acetone by immersing it in an acetone solution (purity ≥99.5%), ensuring the liquid completely covers the sample surface. Set the ultrasonic power to 150–200 W for 5–15 minutes. After the acetone cleaning cycle is complete, transfer the sample to an isopropanol (IPA) solution (purity ≥99.9%), setting the ultrasonic power to 150–200 W for 5–15 minutes. After the isopropanol cleaning cycle is complete, transfer the sample to deionized water (resistivity ≥18.2 MΩ·cm) for further cleaning, setting the ultrasonic power to 50–200 W for 5–15 minutes. After this cycle, transfer the sample to a cleanroom environment and dry it with high-purity nitrogen gas, ensuring no water residue remains on the surface. After cleaning, place the sample in a vacuum oven and dry at 80°C for 30 minutes.

[0091] Step 2 involves fabricating a narrow-band ultraviolet filter. The filter employs an 18-layer structure design of "Air|L(HL)^4 2H(LH)^4|Substruct". Layer H is a high-refractive-index film material made of HfO2, and layer L is a low-refractive-index film material made of SiO2. The thickness of the high-refractive-index layer ranges from 32.23 to 70.82 nm, and the thickness of the low-refractive-index layer ranges from 39.98 to 118.79 nm. The filter exhibits an average ultraviolet light transmittance of over 80.5% in the 360–370 nm wavelength range, with a maximum transmittance of 99.998% at 365.38 nm. The film thicknesses from the glass plate to the air layer are as follows: Substruct|HfO2(44.98nm) / SiO2(63.54nm) / HfO2(48.68nm) / SiO2(65.60nm) / HfO2(48.00nm) / SiO2(70.72nm) / HfO2(52.93nm) / SiO2(74.81nm) / HfO2(70.82nm) / SiO2(67.32nm) / HfO2(48.48nm) / SiO2(70.21nm) / HfO2(44.39nm) / SiO2(62.48nm) / HfO2(44.29nm) / SiO2(39.98nm) / HfO2(32.23nm) / SiO2(118.79nm)|Air. (The remaining text appears to be a fragment and doesn't translate coherently. It likely refers to a specific thickness of the film, but without further context, a precise translation isn't possible.) Figure 5 The transmittance curves for ultraviolet filters in the 360nm–370nm band are shown.

[0092] Step 3, organic cleaning, with the same process and parameters as in Step 1.

[0093] Step 4: Deposit a chromium metal film. A Cr film is deposited on the back of the filter glass plate using magnetron sputtering. The film structure thickness is CrOx / Cr: 20nm / 200nm. The main parameters for the CrOx transition layer deposition process include: gas ratio Ar:O2 = 3:1, total flow rate controlled within 40 sccm, argon flow rate 5–20 sccm, oxygen flow rate 0.5–5 sccm, vacuum range 1.0 x 10⁻³–5 x 10⁻¹ Pa, DC power 100–180 W, substrate temperature room temperature, and sputtering rate controlled at 0.1–10 Å / min to obtain a 20nm thick CrOx layer. The main parameters for the Cr film deposition process include: argon flow rate 10–50 sccm, vacuum range 0.4–0.8 Pa, DC power 100–500 W; sputtering rate: 0.1–5 nm / min, substrate temperature room temperature.

[0094] Step 5: Photolithography patterning. A positive photoresist (AZ5214) is spin-coated onto the CrOx / Cr composite film substrate from the previous step. The main process flow and parameters are: spin-coating speed 4000 rpm, pre-baking temperature 95℃ for 90 seconds, exposure using a SUSS lithography machine, and exposure dose of 190 mJ / cm². 2 ~220mJ / cm 2 The developer used was 2.38% TMAH, the development time was 30s to 45s, and the post-baking was 120℃ for 120 seconds, which finally formed a circular hole array with a diameter of 4μm and a period of 8μm, and a photoresist thickness of about 1.6μm.

[0095] Step 6: Micro-orifice array etching using a dry etching process. Base vacuum pressure ≤ 5 × 10⁻⁵. -6 Torr, process etching gas ratio: Cl2 40 sccm, O2 8 sccm, Ar 10 sccm, RF power 150W, vacuum degree 20mTorr.

[0096] Step 7: Probe substrate preparation. After organic cleaning of the Cr film surface, apply UV adhesive and expose for curing. The cleaning process is the same as in step 1. Apply SU-8 2035 photoresist uniformly to the Cr film surface. Spin coating parameters: 500rpm~800rpm for 5-15 seconds, 1500rpm~3000rpm for 30-60 seconds, adhesive thickness range 30~80μm, thickness uniformity controlled within ±3%. Pre-baking: 65℃~75℃ for 3-5 minutes, 95℃~105℃ for 5-10 minutes. Use a broadband UV light source (mercury lamp intensity 10-20mW / cm²). 2 Perform generalized exposure with an exposure dose of 100–500 mJ / cm². 2 The exposed substrate is placed on a hot plate for post-baking at a temperature of 95℃~105℃ for 5-15 minutes to promote the full progress of the photosensitive cross-linking reaction in the photoresist, enhance the cross-linking density of the exposed area, and reduce residual stress.

[0097] Step 8: Fabrication of the flexible array microprobe. The UV resist film layer from the previous step is cleaned and activated using an O2 / Ar mixed gas (1:3 ratio), with a power of 100–300 W and a pressure of 10–50 Pa. The UV resist film layer undergoes plasma activation treatment for 5–10 minutes to enhance surface adhesiveness. Then, SU-8 2010 negative photoresist is coated again using a two-stage spin-coating process to form a uniform resist layer: 500–800 rpm for 5–15 seconds, and 1500–3000 rpm for 30–60 seconds, forming a photoresist layer with a thickness of 10–20 μm and a thickness uniformity of ≤±3%. Pre-baking is performed at 65–75℃ for 3–5 minutes and at 95–105℃ for 5–10 minutes. Exposure is performed using a broadband lithography machine such as SUSS or EVG, with an exposure dose of 100–500 mJ / cm². 2 Exposure time is 10–60 seconds. Post-baking is performed at 95–105℃ for 5–15 minutes. For development, the substrate is immersed in propylene glycol methyl ether acetate (PGMEA) developer for 2–10 minutes, rinsed with isopropanol (IPA) for 10–30 seconds, and then rinsed with deionized water for 1–3 minutes to remove residual developer. A diffraction field is generated through the circular apertures on the back side, with the light intensity distribution exhibiting Bessel function characteristics, forming a conical light intensity gradient. After development, the photoresist retains the gradient exposure area, forming a high aspect ratio conical flexible array of microneedles.

[0098] Step 9: Separate the membrane layer to obtain a flexible array of microneedles.

[0099] In this embodiment, standard microneedle array data in the 360-370nm band were tested, and the results are as follows:

[0100]

[0101]

[0102] Example 2: High aspect ratio microneedles in the 400-410nm band

[0103] In this embodiment, a 400-410 nm (h-line) ultraviolet narrowband filter was first designed on one side of the quartz glass plate. Then, Cr metal micropores were designed on the other side of the glass plate for light field modulation. Finally, ultraviolet resist was coated on the Cr film to serve as the substrate for the flexible microneedles. After coating with ultraviolet negative photoresist SU-8 2010 and exposure and development, a flexible array of microprobes was formed. The specific steps are as follows:

[0104] Step 1, Organic Cleaning: Clean the JGS1 quartz glass plate. First, pretreat the sample with acetone by immersing it in an acetone solution (purity ≥99.5%), ensuring the liquid completely covers the sample surface. Set the ultrasonic power to 150–200 W for 5–15 minutes. After the acetone cleaning cycle is complete, transfer the sample to an isopropanol (IPA) solution (purity ≥99.9%), setting the ultrasonic power to 150–200 W for 5–15 minutes. After the isopropanol cleaning cycle is complete, transfer the sample to deionized water (resistivity ≥18.2 MΩ·cm) for further cleaning, setting the ultrasonic power to 50–200 W for 5–15 minutes. After this cycle, transfer the sample to a cleanroom environment and dry it with high-purity nitrogen gas, ensuring no water residue remains on the surface. After cleaning, place the sample in a vacuum oven and dry at 80°C for 30 minutes.

[0105] Step 2 involves fabricating a narrow-band ultraviolet filter. The filter employs an 18-layer structure design of "Air|L(HL)^4 2H(LH)^4|Substruct". Layer H is a high-refractive-index film material made of HfO2, and layer L is a low-refractive-index film material made of SiO2. The thickness of the high-refractive-index layer is 36.28–103.38 nm, and the thickness of the low-refractive-index layer is 49.53–81.26 nm. The filter exhibits an average ultraviolet light transmittance of over 85.2% in the 400–410 nm wavelength range, with a maximum transmittance of 99.89% at 404.85 nm. The film thicknesses from the glass plate to the air layer are as follows: Substruct|HfO2(36.28nm) / SiO2(63.04nm) / HfO2(50.44nm) / SiO2(70.20nm) / HfO2(47.13nm) / SiO2(60.28nm) / HfO2(47.40nm) / SiO2(81.26nm) / HfO2(103.38nm) / SiO2(67.63nm) / HfO2(52.84nm) / SiO2(62.53nm) / HfO2(50.31nm) / SiO2(66.17nm) / HfO2(50.37nm) / SiO2(70.49nm) / HfO2(58.58nm) / SiO2(49.53nm)|Air. (The rest of the text appears to be a series of numbers and symbols, possibly related to film thicknesses and thicknesses.) Figure 6 The transmittance curves for ultraviolet filters in the 400nm–410nm band are shown.

[0106] Step 3, organic cleaning, with the same process and parameters as in Step 1.

[0107] Step 4: Deposit a chromium metal film. A Cr film is deposited on the back of the filter glass plate using magnetron sputtering. The film structure thickness is CrOx / Cr: 20nm / 200nm. The main parameters for the CrOx transition layer deposition process include: gas ratio Ar:O2 = 3:1, total flow rate controlled within 40 sccm, argon flow rate 5–20 sccm, oxygen flow rate 0.5–5 sccm, vacuum range 1.0 x 10⁻³–5 x 10⁻¹ Pa, DC power 100–180 W, substrate temperature room temperature, and sputtering rate controlled at 0.1–10 Å / min to obtain a 20nm thick CrOx layer. The main parameters for the Cr film deposition process include: argon flow rate 10–50 sccm, vacuum range 0.4–0.8 Pa, DC power 100–500 W; sputtering rate: 0.1–5 nm / min, substrate temperature room temperature.

[0108] Step 5: Photolithography patterning. A positive photoresist (AZ5214) is spin-coated onto the CrOx / Cr composite film substrate from the previous step. The main process flow and parameters are: spin-coating speed 4000 rpm, pre-baking temperature 95℃ for 90 seconds, exposure using a SUSS lithography machine, and exposure dose of 190 mJ / cm². 2 ~220mJ / cm 2 The developer used was 2.38% TMAH, the development time was 30s to 45s, and the post-baking was 120℃ for 120 seconds, which finally formed a circular hole array with a diameter of 4μm and a period of 8μm, and a photoresist thickness of about 1.6μm.

[0109] Step 6: Micro-orifice array etching using a dry etching process. Base vacuum pressure ≤ 5 × 10⁻⁵. -6 Torr, process etching gas ratio: Cl2 40 sccm, O2 8 sccm, Ar 10 sccm, RF power 150W, vacuum degree 20mTorr.

[0110] Step 7: Probe substrate preparation. After organic cleaning of the Cr film surface, apply UV adhesive and expose for curing. The cleaning process is the same as in step 1. Apply SU-8 2035 photoresist uniformly to the Cr film surface. Spin coating parameters: 500rpm~800rpm for 5-15 seconds, 1500rpm~3000rpm for 30-60 seconds, adhesive thickness range 30~80μm, thickness uniformity controlled within ±3%. Pre-baking: 65℃~75℃ for 3-5 minutes, 95℃~105℃ for 5-10 minutes. Use a broadband UV light source (mercury lamp intensity 10-20mW / cm²). 2 Perform generalized exposure with an exposure dose of 100–500 mJ / cm². 2The exposed substrate is placed on a hot plate for post-baking at a temperature of 95℃~105℃ for 5-15 minutes to promote the full progress of the photosensitive cross-linking reaction in the photoresist, enhance the cross-linking density of the exposed area, and reduce residual stress.

[0111] Step 8: Fabrication of the flexible array microprobe. The UV resist film layer from the previous step is cleaned and activated using an O2 / Ar mixed gas (1:3 ratio), with a power of 100–300 W and a pressure of 10–50 Pa. The UV resist film layer undergoes plasma activation treatment for 5–10 minutes to enhance surface adhesiveness. Then, SU-8 2010 negative photoresist is coated again using a two-stage spin-coating process to form a uniform resist layer: 500–800 rpm for 5–15 seconds, and 1500–3000 rpm for 30–60 seconds, forming a photoresist layer with a thickness of 10–20 μm and a thickness uniformity of ≤±3%. Pre-baking is performed at 65–75℃ for 3–5 minutes and at 95–105℃ for 5–10 minutes. Exposure is performed using a broadband lithography machine such as SUSS or EVG, with an exposure dose of 100–500 mJ / cm². 2 Exposure time is 10–60 seconds. Post-baking is performed at 95–105℃ for 5–15 minutes. For development, the substrate is immersed in propylene glycol methyl ether acetate (PGMEA) developer for 2–10 minutes, rinsed with isopropanol (IPA) for 10–30 seconds, and then rinsed with deionized water for 1–3 minutes to remove residual developer. A diffraction field is generated through the circular apertures on the back side, with the light intensity distribution exhibiting Bessel function characteristics, forming a conical light intensity gradient. After development, the photoresist retains the gradient exposure area, forming a high aspect ratio conical flexible array of microneedles.

[0112] Step 9: Separate the membrane layer to obtain a flexible array of microneedles.

[0113] In this embodiment, high aspect ratio microneedle data in the 400-410nm band were tested, and the results are as follows:

[0114]

[0115] Example 3: Drug-loaded microneedles in the 430-440nm band

[0116] In this embodiment of the invention, a 430-440 nm (g-line) ultraviolet narrowband filter is first designed on one side of a quartz glass plate. Then, Cr metal micropores are designed on the other side of the glass plate for light field modulation. Finally, an ultraviolet resist is coated onto the Cr film as the substrate for the flexible microneedles. After coating with SU-8 2010 ultraviolet negative photoresist and exposure and development, a flexible array of microprobes is formed. The specific steps are as follows:

[0117] Step 1, Organic Cleaning: Clean the JGS1 quartz glass plate. First, pretreat the sample with acetone by immersing it in an acetone solution (purity ≥99.5%), ensuring the liquid completely covers the sample surface. Set the ultrasonic power to 150–200 W for 5–15 minutes. After the acetone cleaning cycle is complete, transfer the sample to an isopropanol (IPA) solution (purity ≥99.9%), setting the ultrasonic power to 150–200 W for 5–15 minutes. After the isopropanol cleaning cycle is complete, transfer the sample to deionized water (resistivity ≥18.2 MΩ·cm) for further cleaning, setting the ultrasonic power to 50–200 W for 5–15 minutes. After this cycle, transfer the sample to a cleanroom environment and dry it with high-purity nitrogen gas, ensuring no water residue remains on the surface. After cleaning, place the sample in a vacuum oven and dry at 80°C for 30 minutes.

[0118] Step 2: Fabrication of a narrow-band ultraviolet filter. The filter employs a 26-layer film structure design of "Air|LH···LH|Substruct". Layer H is a high-refractive-index film material made of HfO2, and layer L is a low-refractive-index film material made of SiO2. The thickness of the high-refractive-index layer is 27.44–146.33 nm, and the thickness of the low-refractive-index layer is 62.36–127.70 nm. The average ultraviolet light transmittance in the 430–440 nm wavelength band reaches over 65.5%, and the maximum transmittance reaches 99.90% at 435.94 nm. The film thicknesses from the glass plate to the air layer are as follows: Substruct|HfO2 (27.44nm) / SiO2 (64.63nm) / HfO2 (146.33nm) / SiO2 (82.10nm) / HfO2 (61.46nm) / SiO2 (79.51nm) / HfO2 (60.30nm) / SiO2 (66.97nm) / HfO2 (48.12nm) / SiO2 (70.1nm) 1nm) / HfO2(43.85nm) / SiO2(63.80nm) / HfO2(142.03nm) / SiO2(62.36nm) / HfO2(44.55nm) / SiO2( 75.71nm) / HfO2(44.37nm) / SiO2(67.30nm) / HfO2(51.54nm) / SiO2(72.82nm) / HfO2(85.10nm) / Si O2(106.10nm) / HfO2(48.55nm) / SiO2(71.27nm) / HfO2(45.89nm) / SiO2(127.70nm)|Air. like Figure 7 The transmittance curves for ultraviolet filters in the 430nm–440nm band are shown.

[0119] Step 3, organic cleaning, with the same process and parameters as in Step 1.

[0120] Step 4: Deposit a chromium metal film. A Cr film is deposited on the back of the filter glass plate using magnetron sputtering. The film structure thickness is CrOx / Cr: 20nm / 200nm. The main parameters for the CrOx transition layer deposition process include: gas ratio Ar:O2 = 3:1, total flow rate controlled within 40 sccm, argon flow rate 5–20 sccm, oxygen flow rate 0.5–5 sccm, vacuum range 1.0 x 10⁻³–5 x 10⁻¹ Pa, DC power 100–180 W, substrate temperature room temperature, and sputtering rate controlled at 0.1–10 Å / min to obtain a 20nm thick CrOx layer. The main parameters for the Cr film deposition process include: argon flow rate 10–50 sccm, vacuum range 0.4–0.8 Pa, DC power 100–500 W; sputtering rate: 0.1–5 nm / min, substrate temperature room temperature.

[0121] Step 5: Photolithography patterning. A positive photoresist (AZ5214) is spin-coated onto the CrOx / Cr composite film substrate from the previous step. The main process flow and parameters are: spin-coating speed 4000 rpm, pre-baking temperature 95℃ for 90 seconds, exposure using a SUSS lithography machine, and exposure dose of 190 mJ / cm². 2 ~220mJ / cm 2 The developer used was 2.38% TMAH, the development time was 30s to 45s, and the post-baking was 120℃ for 120 seconds, which finally formed a circular hole array with a diameter of 4μm and a period of 8μm, and a photoresist thickness of about 1.6μm.

[0122] Step 6: Micro-orifice array etching using a dry etching process. Base vacuum pressure ≤ 5 × 10⁻⁵. -6 Torr, process etching gas ratio: Cl2 40 sccm, O2 8 sccm, Ar 10 sccm, RF power 150W, vacuum degree 20mTorr.

[0123] Step 7: Probe substrate preparation. After organic cleaning of the Cr film surface, apply UV adhesive and expose for curing. The cleaning process is the same as in step 1. Apply SU-8 2035 photoresist uniformly to the Cr film surface. Spin coating parameters: 500rpm~800rpm for 5-15 seconds, 1500rpm~3000rpm for 30-60 seconds, adhesive thickness range 30~80μm, thickness uniformity controlled within ±3%. Pre-baking: 65℃~75℃ for 3-5 minutes, 95℃~105℃ for 5-10 minutes. Use a broadband UV light source (mercury lamp intensity 10-20mW / cm²). 2 Perform generalized exposure with an exposure dose of 100–500 mJ / cm².2 The exposed substrate is placed on a hot plate for post-baking at a temperature of 95℃~105℃ for 5-15 minutes to promote the full progress of the photosensitive cross-linking reaction in the photoresist, enhance the cross-linking density of the exposed area, and reduce residual stress.

[0124] Step 8: Fabrication of the flexible array microprobe. The UV resist film layer from the previous step is cleaned and activated using an O2 / Ar mixed gas (1:3 ratio), with a power of 100–300 W and a pressure of 10–50 Pa. The UV resist film layer undergoes plasma activation treatment for 5–10 minutes to enhance surface adhesiveness. Then, SU-8 2010 negative photoresist is coated again using a two-stage spin-coating process to form a uniform resist layer: 500–800 rpm for 5–15 seconds, and 1500–3000 rpm for 30–60 seconds, forming a photoresist layer with a thickness of 10–20 μm and a thickness uniformity of ≤±3%. Pre-baking is performed at 65–75℃ for 3–5 minutes and at 95–105℃ for 5–10 minutes. Exposure is performed using a broadband lithography machine such as SUSS or EVG, with an exposure dose of 100–500 mJ / cm². 2 Exposure time is 10–60 seconds. Post-baking is performed at 95–105℃ for 5–15 minutes. For development, the substrate is immersed in propylene glycol methyl ether acetate (PGMEA) developer for 2–10 minutes, rinsed with isopropanol (IPA) for 10–30 seconds, and then rinsed with deionized water for 1–3 minutes to remove residual developer. A diffraction field is generated through the circular apertures on the back side, with the light intensity distribution exhibiting Bessel function characteristics, forming a conical light intensity gradient. After development, the photoresist retains the gradient exposure area, forming a high aspect ratio conical flexible array of microneedles.

[0125] Step 9: Separate the membrane layer to obtain a flexible array of microneedles.

[0126] In this embodiment, data on drug-loaded microneedles in the 430-440nm wavelength band were tested, and the results are as follows:

[0127]

[0128] The test data for Examples 1-3 were all from three independent repeated experiments (n≥30), and statistical analysis was performed using OriginPro. Error bars are expressed as ±SD.

[0129] Data analysis of Examples 1-3 shows that: Bessel light field exposure improves feature size control capability by 2.3 times (compared to traditional photolithography); plasma activation treatment increases cell adhesion rate by 41.5% (compared to the untreated group); microneedle height CV on 4-inch wafer is <1.5%, which is better than the industry standard of 5%; the same process platform can simultaneously meet the needs of drug delivery (Example 3) and electrophysiology (Example 4).

[0130] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for fabricating a flexible array microprobe, characterized in that: Includes the following steps: Step S1: Provide a quartz glass substrate and perform organic cleaning treatment. The cleaning process includes three-step ultrasonic cleaning of acetone, isopropanol and deionized water. The ultrasonic power is 50-200W and the time is 5-15 minutes. After cleaning, dry in a vacuum oven at 80℃ for 30 minutes. Step S2: Prepare a narrow-band UV filter film on a quartz glass substrate. The filter film adopts an alternating HfO2 / SiO2 film layer structure, and the film layer design meets the following transmittance requirements: T(λ) ≥ 80% within the target band; And the out-of-band suppression ratio is ≥30dB; Step S3: Cr / CrO is deposited on the other side of the filter film by magnetron sputtering. x Composite metal film; Step S4: Perform photolithography and reactive ion etching (RIE) to form a micron-scale array of circular holes, with the etching selectivity satisfying: ； Where: R Cr R is the Cr etching rate. PR The photoresist etching rate; In Cr / CrO x Positive photoresist is spin-coated onto the film layer, and a micron-scale array of circular holes is formed by photolithography and dry etching. The etching parameters are: etching gas Cl2:O2:Ar=40:8:10sccm, RF power 150W, vacuum degree 20mTorr; the resulting circular holes have a diameter of 5-50μm, a period of 10-200μm, and an aspect ratio ≥5:

1. Step S5: Coat the etched Cr film with UV adhesive and expose and cure it as a probe substrate. Coating parameters: Use SU-8 2000 series or Loctite 3526 UV adhesive; spin coating speed 500-3000 rpm; adhesive layer thickness 50-200 μm; thickness uniformity within ±3%. Step S6: Perform plasma activation treatment on the UV film layer. Treatment parameters: O2 / Ar mixed gas ratio 1:3, power 100-300W, gas pressure 10-50Pa, time 5-10 minutes. Step S7: Coat the activated surface with negative photoresist SU-8 2010, and expose it through a Bessel diffraction light field generated by a micro-aperture array. The light intensity distribution I(r,z) approximates the Bessel function. , where J0 is the zeroth-order Bessel function and α is the light absorption coefficient; Step S8: After development, a high aspect ratio flexible array of microneedles is formed. Development parameters: the developer is propylene glycol methyl ether acetate, and the development time is 2–10 minutes; the resulting microneedle cone angle θ satisfies: ΔI is the radial light intensity change rate; Step S9: Separate the film layers to obtain the final flexible array microneedle structure; The film structure of the ultraviolet narrowband filter in step S2 is any one of the following: a) For the 360-370nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H (LH)^4|Substruct" is adopted, with a film thickness of: Substruct|HfO2 (44.98nm) / SiO2 (63.54nm) / ... / SiO2 (118.79nm)|Air; b) For the 400-410nm wavelength band, an 18-layer structure of "Air|L(HL)^4 2H (LH)^4|Substruct" is adopted, with a film thickness of: Substruct|HfO2 (36.28nm) / SiO2 (63.04nm) / ... / SiO2 (49.53nm)|Air; c) For the 430-440nm wavelength band, a 26-layer structure of "Air|LH···LH|Substruct" is adopted, with a film thickness of: Substruct|HfO2 (27.44nm) / SiO2 (64.63nm) / ... / SiO2 (127.70nm)|Air.

2. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: The optical properties of the micro-aperture array in step S7 satisfy the following relationship: the aperture d and the exposure wavelength λ are: Where NA is the numerical aperture of 0.3 to 0.6; the aperture period p satisfies: δ represents the light field diffusion distance of 1 μm.

3. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: The curing process of the UV adhesive in step S5 satisfies the kinetic model: Where C is the degree of crosslinking, k0 is the pre-exponential factor, and E a η is the activation energy, I is the light intensity, and m / n is the reaction order.

4. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: In step S7, the exposure dose D of the negative photoresist satisfies: Where D0 is the surface dose of 100–500 mJ / cm² 2 L p This represents the depth through which light penetrates.

5. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: In step S6, the ion density nᵢ of the plasma activation treatment satisfies: , in n e For electron density, T e The electron temperature is 2–5 eV.

6. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: The microneedles in step S8 have the following characteristics: 1) Aspect ratio ≥ 5:1; 2) The elastic modulus E satisfies: Where E0 is the bulk material modulus and t / L is the thickness-to-length ratio; 3) Fracture toughness K_IC≥0.8MPa·m^1 / 2.

7. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: In step S3, CrO x The transition layer thickness is 10–30 nm, and the deposition parameters are: Ar:O2 = 3:1, total flow rate ≤ 40 sccm, and vacuum degree 1.0 × 10⁻⁶. -3 ~5×10 -1 Pa; Cr layer thickness 20–190 nm, deposition parameters: argon flow rate 10–50 sccm, vacuum degree 0.4–0.8 Pa.

8. The method for fabricating a flexible array microprobe according to claim 1, characterized in that: In step S2: For the 360-370nm band: average transmittance ≥ 80.5%, peak transmittance ≥ 99.998%@365.38nm; for the 400-410nm band: average transmittance ≥ 85.2%, peak transmittance ≥ 99.89%@404.85nm; for the 430-440nm band: average transmittance ≥ 65.5%, peak transmittance ≥ 99.90%@435.94nm.

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