Micro-nano machining device and micro-nano machining method

Abstract

The embodiment of the invention discloses a micro-nano machining device and a micro-nano machining method, and the micro-nano machining device comprises a laser light source module which is used for outputting femtosecond pulse laser; the light beam adjusting module is arranged on the light emitting side of the laser light source module and is used for carrying out light beam shaping treatment on the femtosecond pulse laser; the scanning module is arranged on the light emitting side of the light beam adjusting module and used for controlling the femtosecond pulse laser to scan in an X-Y plane; the low-numerical-aperture objective lens is arranged on the light emitting side of the scanning module and used for focusing the scanned femtosecond pulse laser, and the numerical aperture NA of the low-numerical-aperture objective lens is larger than or equal to 0.3 and smaller than or equal to 0.7; the motion platform is used for bearing a sample and controlling the sample to move in the Z-axis direction, the sample comprises photoresist, the focused femtosecond pulse laser is converged to the photoresist, the two-photon polymerization reaction of the photoresist is initiated, the cured photoresist forms a micro-nano structure, and the two-photon absorption cross section of the photoresist at a preset wavelength is greater than or equal to 1000GM.

Description

Technical Field

[0001] This application relates to the field of printing technology, and more particularly to a micro / nano fabrication device and a micro / nano fabrication method. Background Technology

[0002] Two-photon polymerization is a technique that uses the nonlinear interaction between a femtosecond pulsed laser and a photosensitive material to print micro- and nano-structures. This technique utilizes a femtosecond pulsed laser to cause a photoinitiator to simultaneously absorb two photons, thus initiating a polymerization reaction. Because two-photon absorption occurs only at the laser focal point, high processing precision can be achieved.

[0003] In related technologies, high numerical aperture (NA>1.0) oil immersion objectives are typically used to achieve high-precision machining. NA objectives can focus the laser into a smaller spot, thereby improving machining resolution. However, NA objectives have a short working distance, typically less than 1 mm, which limits the thickness and range of structures that can be machined. Because NA objectives require an oil immersion medium, oil must be applied between the objective and the sample during operation, and the oil must be cleaned afterward, making the operation complex and prone to sample contamination. Furthermore, the small field of view of NA objectives makes it difficult to cover a large machining area in a single scan, which is unfavorable for machining large-size micro / nano structures. In addition, NA objectives are expensive; a 100x oil immersion objective typically costs more than ten times that of a low-magnification objective.

[0004] Therefore, two-photon polymerization processing is limited in terms of processing field of view, ease of operation and cost, and cannot meet the processing needs of large printing range and high-thickness micro-nano structures. Summary of the Invention

[0005] This application discloses a micro / nano fabrication device and a micro / nano fabrication method to solve the problems of high printing cost, complex operation, and small processing range caused by high numerical aperture oil immersion lenses in related technologies for high-precision processing.

[0006] The first aspect of this application provides a micro / nano fabrication apparatus, comprising: a laser source module for outputting femtosecond pulsed laser light; a beam adjustment module disposed on the light-emitting side of the laser source module for beam shaping of the femtosecond pulsed laser light; a scanning module disposed on the light-emitting side of the beam adjustment module for controlling the femtosecond pulsed laser light to scan in the XY plane; a low numerical aperture objective lens disposed on the light-emitting side of the scanning module for focusing the scanned femtosecond pulsed laser light, wherein the numerical aperture NA of the low numerical aperture objective lens satisfies: 0.3 ≤ NA ≤ 0.7; and a motion platform for carrying a sample and controlling the sample to move in the Z-axis direction, wherein the sample includes photoresist, and the focused femtosecond pulsed laser light converges onto the photoresist, triggering a two-photon polymerization reaction in the photoresist, and the cured photoresist forms a micro / nano structure, wherein the two-photon absorption cross section of the photoresist at a preset wavelength is ≥1000GM.

[0007] In one possible implementation, the laser source module includes: a laser, which uses erbium-doped fiber as the gain medium and is used to output femtosecond pulse seed light with a wavelength of λ1, where λ1 satisfies: 1540nm≤λ1≤1580nm; and a frequency doubling crystal, disposed on the output side of the laser, used to frequency double the femtosecond pulse seed light to a femtosecond pulse laser with a preset wavelength of λ2, where λ2 satisfies: 770nm≤λ2≤790nm.

[0008] In one possible implementation, the femtosecond pulsed laser output by the frequency doubling crystal has a pulse width of <120 fs, a repetition frequency of 100±1 MHz, a maximum output power of >100 mW, a peak power of >1.8 kW, and a beam quality factor M² <1.2.

[0009] In one possible implementation, the beam adjustment module includes: a beam expander for increasing the beam diameter of the femtosecond pulsed laser so that the expanded beam diameter of the femtosecond pulsed laser matches the entrance pupil diameter of the low numerical aperture objective lens; and a rotating beam attenuator located on the output side of the beam expander, the rotating beam attenuator being used to continuously adjust the power of the femtosecond pulsed laser to adjust the power of the femtosecond pulsed laser to be greater than or equal to the threshold power of the two-photon polymerization reaction of the photoresist, wherein the femtosecond pulsed laser power P ≥ 2.2 mW.

[0010] In one possible implementation, the scanning module includes a scanning galvanometer for controlling the femtosecond pulsed laser to scan in the XY plane, wherein the XY plane scanning range D of the scanning galvanometer satisfies: 180μm≤D≤220μm.

[0011] In one possible implementation, the micro / nano fabrication device further includes a dual telecentric optical module disposed between the scanning module and the low numerical aperture objective lens. The dual telecentric optical module is used to collimate and eliminate aberrations of the beam output by the scanning module so that the femtosecond pulsed laser is perpendicularly incident on the low numerical aperture objective lens.

[0012] In one possible implementation, the dual telecentric optical module includes: a scanning lens for converging the femtosecond pulsed laser output by the scanning module; and a sleeve lens disposed on the light-emitting side of the scanning lens for collimating the beam converged by the scanning lens into parallel light for emission.

[0013] In one possible implementation, the micro / nano fabrication device further includes: a light source for emitting illumination light onto the sample; a dichroic mirror disposed on the incident light side of the low numerical aperture objective lens for transmitting fluorescence generated by the photoresist; and an imaging module disposed on the reflected light path of the dichroic mirror for acquiring fabrication images of the fabricated area.

[0014] In one possible implementation, the wavelength λ2 of the femtosecond pulsed laser output by the beam adjustment module satisfies: 770nm≤λ2≤790nm.

[0015] In one possible implementation, the beam adjustment module adjusts the power P of the femtosecond pulsed laser to 2.2mW ≤ P ≤ 5mW.

[0016] In one possible implementation, the scanning module adjusts the scanning speed of the femtosecond pulsed laser to 60 μm / s ≤ v ≤ 70 μm / s.

[0017] In one possible implementation, the fabrication linewidth of the micro / nano structure is ≤80nm.

[0018] An embodiment of the second aspect of this application provides a micro / nano fabrication method, the method comprising: fixing a sample containing photoresist on a motion platform, wherein the photoresist has a two-photon absorption cross section ≥1000GM at a preset wavelength; activating a laser source module and outputting a femtosecond pulsed laser, and performing beam shaping processing on the femtosecond pulsed laser through a beam adjustment module; in the current layer, controlling the adjusted femtosecond pulsed laser to scan in the XY plane according to a preset scanning path through a scanning module; after scanning the current layer, controlling the sample to move a distance of one layer thickness in the Z-axis direction through the motion platform and controlling the scanning module to scan the next layer, until all layers are scanned to obtain a micro / nano structure.

[0019] In one possible implementation, the micro / nano fabrication method further includes: receiving a three-dimensional model of the micro / nano structure generated by three-dimensional modeling software; performing 2D slicing and layered scattering processing on the three-dimensional model to generate the preset scanning path containing the scanning pattern of each layer.

[0020] The micro / nano fabrication apparatus provided in this application achieves two-photon polymerization processing without relying on high-numerical-aperture oil immersion objectives by using a low numerical aperture objective lens in conjunction with a photoresist with a two-photon absorption cross-section ≥1000GM at a preset wavelength. Compared with scanning schemes that rely on high-numerical-aperture oil immersion objectives (NA>1.0), the micro / nano fabrication apparatus provided in this application provides a larger field of view, covering an area of ​​approximately 200μm in a single scan, which is beneficial for processing large-size micro / nano structures. The working distance is longer, reaching 2-9mm, enabling the processing of thicker samples while reducing the risk of collision between the low-numerical-aperture objective lens and the sample. Operation is also simpler, eliminating the need for an oil immersion medium and avoiding potential sample contamination from oil. Furthermore, the cost of the micro / nano fabrication apparatus is lower; the price of a low-numerical-aperture objective lens may be less than one-tenth that of an oil immersion objective lens. Based on this, the micro-nano fabrication device provided in this application embodiment can achieve a maximum lateral spatial resolution of 76nm and a fabrication linewidth of less than 80nm. While maintaining high fabrication accuracy, it solves the limitation that high-precision fabrication must rely on high numerical aperture oil immersion lenses.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a micro / nano fabrication device provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a dual telecentric optical module in a micro / nano fabrication device provided in an embodiment of this application; Figure 3 Linewidth test results of a micro / nano fabrication device under different process parameters provided in this application embodiment; Figure 4 A schematic flowchart of a micro / nano fabrication method provided in an embodiment of this application; Figure 5A magnified microscope image of a micro-nano structure fabricated by a micro-nano fabrication device according to an embodiment of this application.

[0024] Explanation of reference numerals in the attached figures: 1-Micro / nano fabrication device; 10-Laser source module; 20-Beam adjustment module; 201-Beam expander; 202-Rotating beam attenuator; 30-Scanning module; 301-Scanning galvanometer; 40-Low numerical aperture objective lens; 50-Motion platform; 60-Sample; 601-Substrate; 602-Photoresist; 80-Dual telecentric optical module; 801-Scanning lens; 802-Sleeve lens; C-Scanning plane; B-Intermediate plane; A-Object plane; 90-Dichroic mirror; 100-Imaging module; 200-Light source; 70-Second filter; 300-Focusing lens. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0027] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0028] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0029] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0030] The first aspect of this application provides a micro / nano fabrication device 1, including a laser source module 10, a beam adjustment module 20, a scanning module 30, a low numerical aperture objective lens 40, a motion platform 50, and a sample 60.

[0031] The laser source module 10 is used to output femtosecond pulsed laser light. Femtosecond pulsed laser light refers to laser light with a pulse width on the order of femtoseconds (10⁻¹⁰). - ¹ 5 Femtosecond lasers are characterized by short pulse widths and high peak power. High peak power is a necessary condition for achieving two-photon absorption, because two-photon absorption requires two photons to arrive at the photoinitiator molecule simultaneously, and two-photon absorption requires a sufficiently high photon density to occur.

[0032] The beam shaping module 20 is located on the light-emitting side of the laser source module 10. The beam shaping module 20 is used to perform beam shaping processing on the femtosecond pulsed laser. Beam shaping can include beam expansion, filtering, and power adjustment. Beam expansion refers to increasing the diameter of the femtosecond pulsed laser beam so that the expanded beam diameter matches the entrance pupil diameter of the subsequent objective lens, thereby fully utilizing the numerical aperture of the objective lens. Filtering refers to removing unwanted wavelength components from the laser. Power adjustment refers to continuously adjusting the laser power so that the femtosecond pulsed laser reaches the two-photon polymerization reaction threshold of the photoresist 602.

[0033] The scanning module 30 is located on the light-emitting side of the beam adjustment module 20 and is used to control the femtosecond pulsed laser to scan in the XY plane. The scanning module 30 rapidly deflects the direction of the laser beam, causing the focal point of the femtosecond pulsed laser to move on the sample along a preset path, thereby realizing the processing of two-dimensional graphics.

[0034] A low numerical aperture objective lens 40 is positioned on the light-emitting side of the scanning module 30 to focus the scanned femtosecond pulsed laser. The numerical aperture NA of the low numerical aperture objective lens 40 satisfies the condition: 0.3 ≤ NA ≤ 0.7. Numerical aperture (NA) is a parameter characterizing the focusing ability of an objective lens, defined as NA = n·sinθ, where n is the refractive index of the medium between the objective lens and the sample, and θ is half the aperture angle of the objective lens. A larger numerical aperture results in stronger focusing ability and a smaller focused spot, but also a shorter working distance.

[0035] The low numerical aperture objective 40 can be an air objective. An air objective refers to an objective where the medium between the objective and the sample is air, eliminating the need for an oil immersion medium. Compared to oil immersion objectives, air objectives are simpler to operate, eliminating the need for applying oil before each use and cleaning oil residue afterward, thus avoiding potential sample contamination. Furthermore, air objectives have a longer working distance, typically on the order of millimeters, while oil immersion objectives usually have a working distance of less than 1 millimeter. Therefore, air objectives are more suitable for processing thicker samples and reduce the risk of collision between the objective and the sample. In addition, air objectives are relatively inexpensive, contributing to a reduction in the overall cost of the micro / nano fabrication device 1.

[0036] Specifically, the NA value of the low numerical aperture objective lens 40 can be 0.3, 0.4, 0.5, 0.6, or 0.7.

[0037] In one specific embodiment, the NA value of the low numerical aperture objective lens 40 can be 0.4. An objective lens with NA=0.4 is a low-magnification objective lens, with a working distance of 2-9 mm, which is higher than that of a high numerical aperture oil immersion objective lens (typically less than 1 mm). Therefore, it can process thicker samples and reduces the risk of collision between the objective lens and the sample. Simultaneously, this objective lens does not require an oil immersion medium, using air directly as the imaging medium, avoiding oil contamination of the sample and simplifying the operation process. Furthermore, the low numerical aperture objective lens 40 with NA=0.4 has a wider field of view, covering an area of ​​approximately 200 μm in a single scan, reducing the number of stitching operations and facilitating the fabrication of large-sized micro / nano structures. In terms of cost, the price of a 20x low numerical aperture objective lens 40 (NA=0.4) is typically less than one-tenth that of a 100x oil immersion objective lens, reducing the cost of the micro / nano fabrication device 1.

[0038] The motion platform 50 is used to carry the sample 60 and control its movement in the Z-axis direction. The Z-axis direction is perpendicular to the XY plane, which is the stacking direction of the fabricated structure. By moving the motion platform 50 along the Z-axis, layer-by-layer fabrication can be achieved, thereby constructing a three-dimensional micro / nano structure.

[0039] Sample 60 includes photoresist 602. Photoresist 602 can be disposed on substrate 601. Photoresist 602 is a photosensitive material that undergoes a polymerization reaction under laser irradiation. The focused femtosecond pulse laser converges to the photoresist 602, initiating a two-photon polymerization reaction in the photoresist 602, and the cured photoresist 602 forms a micro / nano structure.

[0040] The photoresist 602 used in this embodiment contains the two-photon initiator FO2. FO2 is a carboxylate two-photon dye with a fluorene ring parent structure, and its chemical name is 2,2'. ((((1E,1'E) (9,9 Bis(2 (2 (2-methoxyethoxy)ethyl) 9H Fluorene 2,7 Diyl)bis(ethylene 2,1 Diyl))bis(4,1 Phenylene))bis(methanediyl)bis(acetate sodium). The two-photon initiator FO2 has good water solubility. Its single-photon absorption peak in aqueous solution is 405 nm, the emission peak is at 540 nm, and the two-photon emission peak is at 571 nm.

[0041] The two-photon absorption cross-section of the photoresist 602 at the preset wavelength is ≥1000 GM. The two-photon absorption cross-section (Two-photon absorption cross-section) is a physical quantity that characterizes the ability of a photoinitiator to absorb two photons. The unit is Goeppert-Mayer (GM), and 1 GM = 10 -50 cm 4 ·s·photon - ¹·molecule - ¹. The larger the absorption cross-section of the photoresist 602, the higher the absorption efficiency of two photons, and the easier it is to initiate a polymerization reaction under the same laser power. The preset wavelength can be selected between 770 nm and 790 nm. Specifically, the preset wavelength can be 780 nm.

[0042] The two-photon initiator FO2 used in the embodiments of this application has a relatively high two-photon absorption cross-section (≥1000 GM). A relatively high two-photon absorption cross-section means that under the same laser power conditions, the two-photon initiator FO2 can more efficiently capture two photons in the femtosecond pulsed laser and initiate a polymerization reaction. This enables the micro-nano processing device 1 provided by the embodiments of this application to achieve two-photon polymerization processing under relatively low laser power (2.2 - 2.5 mW). Even for the spot generated by focusing with a low numerical aperture objective lens 40 (NA ≤ 0.7), the two-photon initiator FO2 in the focal region can still efficiently absorb the two-photon energy, confining the two-photon polymerization reaction to the central region of the focus.

[0043] Specifically, the two-photon absorption cross-section of photoresist 602 can reach 1184 GM at 780 nm. This wavelength matches the 780 nm femtosecond pulsed laser used in one embodiment of this application. When the 780 nm femtosecond pulsed laser is focused onto the photoresist 602 containing the two-photon initiator FO2 by the low numerical aperture objective lens 40, the high absorption cross-section of the two-photon initiator FO2 near this wavelength ensures the efficiency of two-photon absorption, providing a material basis for achieving high processing accuracy under the conditions of the low numerical aperture objective lens 40.

[0044] Thus, the micro / nano fabrication device 1 provided in this application embodiment can achieve high processing accuracy under the condition of a low numerical aperture objective lens 40, and the processing linewidth of the fabricated micro / nano structure can be less than 80 nm, with a maximum lateral spatial resolution of 76 nm.

[0045] Furthermore, the two-photon initiator FO2 not only possesses a high two-photon absorption cross section but also exhibits low biotoxicity and good cell permeability. The fluorescence quantum yield of FO2 is 2.1% in water, 89.0% in DMSO, and 62.9% in ethanol. In addition, FO2 demonstrates good mitochondrial recognition, enabling co-localization with the mitochondrial dye Mito Tracker Deepred in the C6 cell line, with a Pearson co-localization coefficient of 0.90 and a Mander overlap coefficient of 0.95. These properties allow FO2 to efficiently initiate two-photon polymerization reactions even under low laser power conditions.

[0046] Thus, the micro / nano fabrication apparatus 1 provided in this application embodiment achieves two-photon polymerization processing without relying on a high numerical aperture oil immersion objective by using a low numerical aperture objective lens 40 in conjunction with a photoresist 602 with a two-photon absorption cross-section ≥1000GM at a preset wavelength. Compared with scanning schemes that rely on high numerical aperture oil immersion objectives (NA>1.0), the micro / nano fabrication apparatus 1 provided in this application embodiment has a larger processing field of view, covering an area of ​​about 200μm in a single scan, which is beneficial for processing large-size micro / nano structures. The working distance is longer, reaching 2-9mm, enabling the processing of thicker samples while reducing the risk of collision between the low numerical aperture objective lens 40 and the sample. Operation is also simpler, eliminating the need for an oil immersion medium and avoiding potential oil contamination of the sample. Furthermore, the cost of the micro / nano fabrication apparatus 1 is lower; the price of the low numerical aperture objective lens 40 may be less than one-tenth of that of an oil immersion objective. Based on this, the micro-nano fabrication device 1 provided in this application embodiment can achieve a maximum lateral spatial resolution of 76nm and a fabrication linewidth of less than 80nm. While maintaining high fabrication accuracy, it solves the limitation brought about by high numerical aperture oil immersion lenses that high-precision fabrication must rely on.

[0047] In some embodiments, the power P of the femtosecond pulsed laser adjusted by the beam adjustment module 20 is ≥2.2mW.

[0048] Two-photon polymerization occurs only when the power of the femtosecond pulsed laser reaches or exceeds the threshold power of the photoresist 602. The threshold power of the photoresist 602 is related to factors such as the absorption cross section of the photoinitiator in the photoresist 602 and the laser pulse width.

[0049] Under the laser parameters of the two-photon initiator FO2 and the aforementioned femtosecond pulsed laser, the threshold power for the two-photon polymerization reaction is 2.2mW-2.5mW. The beam adjustment module 20 controls the laser power within a range greater than or equal to 2.2mW, ensuring that the threshold power is reached to initiate the polymerization reaction.

[0050] The reason why the power P is required to be ≥2.2mW is that when the laser power is lower than 2.2mW, it may not be able to reach the threshold power of the photoresist 602, which will prevent the two-photon polymerization reaction from occurring; when the laser power is higher than 2.5mW, the curing area at the focal point will expand, resulting in a thicker processing linewidth and affecting the processing accuracy of micro and nano structures.

[0051] Furthermore, to balance processing efficiency and precision, the power P of the femtosecond pulsed laser can be selected within the range of 2.2mW ≤ P ≤ 2.5mW. Within this power range, the laser energy can meet the threshold requirements of the two-photon polymerization reaction, ensuring sufficient curing of the photoresist. At the same time, it avoids energy oversaturation at the focal point due to excessive power, thereby preventing excessive diffusion in the cured area, linewidth thickening, and potential thermal damage, ensuring the processing precision of the micro / nano structures.

[0052] In some embodiments, the wavelength λ2 of the femtosecond pulsed laser output by the beam adjustment module 20 satisfies: 770nm ≤ λ2 ≤ 790nm. Specifically, λ2 can be 780nm.

[0053] The wavelength of the femtosecond pulsed laser needs to match the two-photon absorption peak wavelength of the photoinitiator in the photoresist 602. The photoresist 602 used in this embodiment contains a two-photon initiator FO2, which has a high two-photon absorption cross-section (up to 1184 GM) at 780 nm. Controlling the wavelength of the femtosecond pulsed laser within the range of 770 nm to 790 nm covers the two-photon absorption peak region of the two-photon initiator FO2, enabling the photoresist 602 to efficiently absorb two-photon energy under femtosecond pulsed laser irradiation, thereby initiating a two-photon polymerization reaction.

[0054] If the wavelength of the femtosecond pulsed laser deviates from this range, the two-photon absorption efficiency of the two-photon initiator FO2 will decrease, and it may not be able to reach the threshold power under the same laser power conditions, resulting in the two-photon polymerization reaction being difficult to occur or the processing efficiency being reduced.

[0055] Therefore, controlling the wavelength of the femtosecond pulsed laser within the range of 770nm to 790nm can ensure that the two-photon initiator FO2 in the photoresist 602 efficiently absorbs two-photon energy, providing an energy basis for two-photon polymerization processing under the conditions of a low numerical aperture objective lens 40.

[0056] In one possible implementation, the scanning module 30 adjusts the scanning speed v of the femtosecond pulse laser to 60 μm / s ≤ v ≤ 70 μm / s.

[0057] Scanning speed refers to the speed at which the laser focus moves across the sample, and it determines the exposure time for each laser focus. With a fixed power for the femtosecond pulsed laser, a slower scanning speed results in a longer exposure time and a wider cured linewidth; conversely, a faster scanning speed results in a shorter exposure time and a narrower cured linewidth.

[0058] To determine the optimal processing technology, the micro / nano fabrication device 1 of this application under different combinations of laser power and scanning speed was tested for linewidth, such as... Figure 3 As shown, experimental results indicate that the minimum processing linewidth (62.1 nm) can be obtained when the laser power is 2.2 mW and the scanning speed is 70 μm / s. A processing linewidth of 75.6 nm can be obtained when the laser power is 2.2 mW and the scanning speed is 60 μm / s.

[0059] When the power is too high or the speed is too slow, the processing linewidth will increase significantly. Therefore, this application preferably controls the power range between 2.2mW and 2.5mW, and the scanning speed is 60μm / s-70μm / s. Under these conditions, a linewidth below 80nm can be obtained, and the highest lateral resolution can reach 76nm. When a wider processing linewidth is required, the laser power can be appropriately increased or the scanning speed can be decreased to adjust the size of the curing area, thereby meeting the processing linewidth requirements of different Wiener structures. In the embodiments of this application, the power P of the femtosecond pulsed laser can be taken as: 2.2mW≤P≤2.5mW, which is at a relatively low level. In order to reach the threshold energy of the photoresist 602 and achieve sufficient curing of the photoresist 602 under low power conditions, a relatively slow scanning speed is required to increase the exposure time. Experiments have shown that when the power P of the femtosecond pulsed laser is 2.2mW and the scanning speed is maintained at 60μm / s≤v≤70μm / s, it is possible to ensure that the photoresist 602 is fully cured while keeping the cured area within a small range, thus achieving better processing results.

[0060] If the scanning speed is too fast, the exposure time will be insufficient, which may lead to incomplete two-photon polymerization. If the scanning speed is too slow, the exposure time will be too long, which will cause the solidified area to diffuse, the line width to become thicker, and the processing accuracy to be affected. Specifically, the scanning module 30 can adjust the scanning speed v of the femtosecond pulsed laser to 60μm / s, 65μm / s, or 70μm / s.

[0061] In some embodiments, under the conditions that the power P of the femtosecond pulsed laser satisfies: 2.2mW≤P≤2.5mW and the scanning speed v satisfies: 60μm / s≤v≤70μm / s, the fabrication linewidth of the micro / nano structure is ≤80nm.

[0062] Processing linewidth refers to the width of the smallest line of a micro-nano structure that the micro-nano processing device 1 can process, and it is an indicator for measuring processing accuracy.

[0063] For example, the processing linewidth can be 76 nm. The processing linewidth of micro-nano structures is ≤80 nm, which means that the micro-nano processing device 1 provided in this application embodiment can process micro-nano structures with a laser wavelength (780 nm) smaller than that of femtosecond pulsed lasers, thus breaking the diffraction limit.

[0064] In some embodiments, the laser source module 10 includes a laser and a frequency doubling crystal.

[0065] Lasers can use erbium-doped fiber as the gain medium; that is, lasers can be erbium-doped fiber lasers. Erbium-doped fiber is made by doping erbium ions (Er³⁺) into the fiber core. + In erbium-doped fiber lasers, the stimulated emission wavelength of erbium ions is around 1540 nm, so erbium-doped fiber lasers can output laser light at around 1560 nm. Erbium-doped fiber lasers are used to output femtosecond pulse seed light with a wavelength of λ1, where λ1 satisfies: 1540 nm ≤ λ1 ≤ 1580 nm. Specifically, λ1 can be 1560 nm.

[0066] A frequency-doubling crystal is placed on the output side of an erbium-doped fiber femtosecond pulse laser to frequency-double the femtosecond pulse seed light to a predetermined wavelength λ2, where λ2 satisfies: 770nm ≤ λ2 ≤ 790nm. Frequency doubling is a nonlinear optical effect in which two photons with frequency ω interact to produce a photon with frequency 2ω. By frequency doubling, a 1560nm femtosecond pulse laser can be converted into a 780nm femtosecond pulse laser to match the two-photon absorption peak wavelength of the photoresist 602.

[0067] The frequency doubling crystal can be a PPLN (Periodically Polarized Lithium Niobate) crystal. PPLN is a nonlinear optical crystal prepared using periodic polarization technology. PPLN crystals have a high nonlinear coefficient and a wide transparency range, achieving high conversion efficiency in the frequency doubling process from 1560 nm to 780 nm. Using a PPLN frequency doubling crystal can further reduce the requirements for the light source while ensuring sufficient laser power, helping to control the overall cost of the laser source module 10.

[0068] In one possible implementation, the femtosecond pulsed laser output by the laser source module 10 (frequency doubling crystal) has a pulse width > 120 fs, a repetition frequency of 100 ± 1 MHz, a maximum output power > 100 mW, a peak power > 1.8 kW, and a beam quality factor M² < 1.2.

[0069] A pulse width > 120 fs indicates that each laser pulse has an extremely short duration, resulting in highly compressed energy over time and a high instantaneous power density at the focal point. A repetition frequency of 100 ± 1 MHz refers to the number of pulses output per second, determining the number of times the femtosecond pulsed laser exposes the sample per unit time, thus affecting processing efficiency. A maximum output power > 100 mW (milliwatts) refers to the average power the laser can output, reflecting its overall output capability. A peak power > 1.8 kW is the instantaneous power of each pulse, calculated by dividing the pulse energy by the pulse width. It is a parameter determining two-photon absorption efficiency; the higher the peak power, the greater the photon density at the focal point, and the easier it is for two-photon absorption to occur. The beam quality factor M² measures the quality of the laser beam. M² = 1 represents an ideal Gaussian beam. The closer the M² value is to 1, the better the beam quality, and the easier it is for the femtosecond pulsed laser to be focused into a near-diffraction-limited, extremely small spot.

[0070] In this way, the above factors together ensure that the femtosecond pulsed laser can be focused into an extremely small spot and provide a sufficiently high photon density at the focal point, thereby efficiently initiating a two-photon polymerization reaction.

[0071] In some embodiments, the beam adjustment module 20 includes a beam expander 201 and a rotating beam attenuator 202 arranged sequentially along the optical path. Arranging them sequentially along the optical path means that the components are arranged in order according to the propagation direction of the femtosecond pulse laser, passing first through the beam expander 201 and then through the rotating beam attenuator 202.

[0072] The beam expander 201 is used to increase the beam diameter of the femtosecond pulsed laser so that the expanded beam diameter matches the entrance pupil diameter of the low numerical aperture objective lens 40. The entrance pupil diameter is the diameter of the entrance pupil of the objective lens. Only when the incident beam diameter matches the entrance pupil diameter can the numerical aperture of the objective lens be fully utilized; otherwise, resolution loss will occur.

[0073] The rotating beam attenuator 202 is used to continuously adjust the power of the femtosecond pulse laser to bring the power of the femtosecond pulse laser close to the threshold power of the two-photon polymerization reaction of the photoresist 602, where the power P satisfies: 2.2mW≤P≤2.5mW.

[0074] Two-photon polymerization occurs only when the laser power reaches or exceeds the threshold power for two-photon polymerization of photoresist 602. The threshold power is related to factors such as the absorption cross-section of the photoinitiator in photoresist 602 and the laser pulse width. This application experimentally determined the threshold power (mW) for two-photon polymerization under the conditions of two-photon initiator FO2 and the aforementioned laser parameters. The threshold power of photoresist 602 satisfies: 2.2mW ≤ P ≤ 2.5mW. Therefore, a femtosecond pulsed laser power reaching the threshold power of photoresist 602 can successfully initiate the two-photon polymerization reaction of photoresist 602.

[0075] In some embodiments, the beam adjustment module 20 further includes a first filter. The first filter is disposed between the beam expander 201 and the rotating beam attenuator 202. The first filter can be a bandpass filter in the 770nm~790nm band, used to transmit femtosecond pulsed laser light with a preset wavelength λ2 and filter out the 1560nm fundamental frequency light remaining during the frequency doubling process. The fundamental frequency light refers to the 1560nm femtosecond pulsed laser light before frequency doubling. If the remaining fundamental frequency light enters the processing optical path, it may interfere with the two-photon polymerization process or generate additional thermal effects.

[0076] In some embodiments, the micro / nano fabrication device 1 further includes a first reflector 1001. The first reflector 1001 is disposed on the light-emitting side of the beam adjustment module 20 and is used to adjust the direction of the femtosecond pulsed laser emitted by the beam adjustment module 20 so as to align with the optical path of subsequent optical modules (such as the scanning module 30). By setting the first reflector 1001, the entire optical path layout can be made more compact and flexible, facilitating the installation and debugging of each module.

[0077] In some embodiments, the micro / nano fabrication device 1 further includes a second reflector 1002. The second reflector 1002 is disposed on the light-emitting side of the first reflector 1001, and is used to readjust the propagation direction of the femtosecond pulsed laser after its orientation has been adjusted by the first reflector 1001, ensuring its accurate incidence on the subsequent scanning module 30. Through the cooperation of the first reflector 1001 and the second reflector 1002, the optical path can be flexibly arranged within a limited space, making the propagation path of the femtosecond pulsed laser more compact, facilitating the installation and debugging of each module, while ensuring the pointing accuracy of the laser beam and the stability of the optical path. In one possible implementation, the scanning module 30 includes a scanning galvanometer 301. The scanning galvanometer 301 is located on the light-emitting side of the second reflector 1002.

[0078] The scanning galvanometer 301 is a beam scanning device that uses a galvanometer-type motor to drive a reflecting mirror. The scanning galvanometer 301 internally includes two orthogonally placed reflecting mirrors, corresponding to the X and Y axes respectively. When the controller of the micro / nano fabrication structure applies a voltage signal to the scanning galvanometer 301, the motor drives the reflecting mirrors to produce a corresponding angular deflection, thereby changing the reflection direction of the femtosecond pulsed laser. By controlling the coordinated movement of the two reflecting mirrors, the laser beam can achieve rapid and precise two-dimensional scanning in the XY plane.

[0079] The scanning galvanometer 301 is used to control the high-speed deflection and scanning of femtosecond pulsed lasers in the XY plane. Compared with moving the sample, the scanning galvanometer 301 has the advantages of fast response speed, high positioning accuracy, and low motion inertia. It can complete the scanning of complex paths in milliseconds, making it suitable for the rapid fabrication of micro and nanostructures.

[0080] In some embodiments, the XY plane scanning range D of the scanning galvanometer 301 satisfies: 180μm≤D≤220μm. The scanning range refers to the diameter of the area that the laser focus can cover in the XY plane. In this embodiment, the scanning range of the scanning galvanometer 301 can be approximately 200μm.

[0081] It should be noted that the scanning range of the scanning galvanometer 301 is directly related to the field of view of the objective lens. Since this embodiment uses a low numerical aperture objective lens 40, which has a lower magnification, its field of view is typically larger than that of a high numerical aperture objective lens. Therefore, the scanning galvanometer 301 can cover a larger processing area in a single scan, reducing the number of stitching operations required for processing large structures, thus improving processing efficiency and the quality of micro / nano structures.

[0082] In one possible implementation, the micro / nano fabrication device 1 further includes a dual telecentric optical module 80. The dual telecentric optical module 80 is disposed between the scanning module 30 and the low numerical aperture objective lens 40.

[0083] When the scanning module 30 is working, it controls the beam direction of the femtosecond pulsed laser by deflecting the reflective mirror. When the scanning module 30 deflects the femtosecond pulsed laser beam to different angles, the emitted beam of the femtosecond pulsed laser will have a corresponding angular change. Without the dual telecentric optical module 80, these femtosecond pulsed laser beams with different angles would directly enter the low numerical aperture objective lens 40. In this case, only the beam in the central region of the field of view of the low numerical aperture objective lens 40 can be perpendicularly incident on the back focal plane of the low numerical aperture objective lens 40, while the beam in the edge region of the field of view will be incident at an oblique angle. Oblique incident will lead to increased aberrations in the edge field of view, distortion of the focused spot, and decreased resolution, resulting in inconsistent accuracy within the processing field of view and affecting the processing quality of micro and nanostructures.

[0084] The dual telecentric optical module 80 is used to collimate and eliminate aberrations in the beam output from the scanning module 30. Specifically, the dual telecentric optical module 80 can convert the femtosecond pulsed laser beam with angle variation output from the scanning module 30 into a parallel beam, and ensure that these parallel beams are always perpendicularly incident on the back focal plane of the low numerical aperture objective lens 40 along the optical axis.

[0085] In this way, the dual telecentric optical module 80 can ensure that, throughout the entire scanning range, no matter what angle the scanning module 30 deflects the femtosecond pulse laser beam, the beam that finally enters the low numerical aperture objective lens 40 remains in a perpendicular incident state. This eliminates the aberrations of the low numerical aperture objective lens 40 at the edge of the scanning field of view, ensuring that the size and shape of the focused spot within the field of view remain consistent, thereby guaranteeing the consistency of resolution within the processing area.

[0086] In some embodiments, the dual telecentric optical module 80 includes a scanning lens 801 and a sleeve lens 802.

[0087] A scanning lens 801 is disposed on the light-emitting side of the scanning module 30. It is used to receive and focus the femtosecond pulsed laser output from the scanning module 30. The scanning lens 801 can be a positive lens. When the femtosecond pulsed laser beams with different angles output from the scanning module 30 enter the scanning lens 801, the scanning lens 801 will focus the femtosecond pulsed laser beams with different angles to different positions on its rear focal plane, converting the angle change of the femtosecond pulsed laser beam into a position change.

[0088] A sleeve lens 802 is disposed on the light-emitting side of the scanning lens 801 to collimate the beam converged by the scanning lens 801 back into parallel light for emission. The sleeve lens 802 can also be a positive lens; the diverging beam emitted from each point on the rear focal plane of the scanning lens 801 is converted into a parallel beam after passing through the sleeve lens 802. Since the points on the rear focal plane of the scanning lens 801 correspond one-to-one with the angle of the incident beam, the direction of the parallel beam emitted through the sleeve lens 802 also corresponds one-to-one with the angle of the incident beam, but in this case, all emitted beams are parallel to the optical axis.

[0089] The dual telecentric optical module 80 and the low numerical aperture objective lens 40 constitute a dual telecentric optical path structure. "Dual telecentric" has two meanings: first, object-side telecentricity, meaning the principal ray of the femtosecond pulsed laser beam emitted from the low numerical aperture objective lens 40 is parallel to the optical axis; second, image-side telecentricity, meaning the principal ray of the femtosecond pulsed laser beam entering the low numerical aperture objective lens 40 is parallel to the optical axis. In this embodiment, the parallel beam emitted from the sleeve lens 802 is perpendicularly incident on the low numerical aperture objective lens 40, ensuring image-side telecentricity. Furthermore, after the low numerical aperture objective lens 40 focuses the perpendicularly incident parallel beam, the principal ray of the beam on its focal plane is also parallel to the optical axis, ensuring object-side telecentricity.

[0090] Through the combination of scanning lens 801 and sleeve lens 802, the laser beam with angle variation output from scanning module 30 is converted into a set of parallel beams that are perpendicularly incident on low numerical aperture objective lens 40. The low numerical aperture objective lens 40 then focuses the beam to form a focused spot with parallel principal rays in the field of view, thus forming a dual telecentric optical path structure. This structure ensures that the size and shape of the focused spot remain consistent within the scanning field of view, eliminating aberrations and resolution degradation caused by oblique beam incidence, and guaranteeing consistent resolution within the processing area.

[0091] In some embodiments, such as Figure 2 As shown, the distance from the scanning plane C to the scanning lens 801 is L1, L1 = 37.8 mm, and the light-transmitting aperture D1 of the scanning lens 801 is 4.0 mm. The distance between the scanning lens 801 and the intermediate plane B is L2, L2 = 26.4 mm. The effective aperture or diameter D2 of the scanning lens 801 is 2.00" (approximately 50.9 mm).

[0092] In some embodiments, such as Figure 2 As shown, the distance from the intermediate plane B to the sleeve lens 802 is L3, L3 = 148.0 mm. The effective aperture or diameter D3 of the sleeve lens 802 is 1.74" (approximately 44.1 mm). The distance from the sleeve lens 802 to the object plane A is L4, L4 = 228.0 mm, and the maximum scanning field size on the object plane A is D4, with a maximum value of 25.0 mm.

[0093] In some possible embodiments, such as Figure 1 As shown, the micro / nano fabrication device 1 also includes a dichroic mirror 90. Along the emission direction of the femtosecond pulsed laser ( Figure 1 (The red optical path shown) The dichroic mirror 90 is located between the low numerical aperture objective lens 40 and the double telecentric optical module 80.

[0094] Dichroic mirror 90 has high transmittance for 780nm femtosecond pulsed lasers, allowing them to pass smoothly into low numerical aperture objective lens 40 and be focused onto photoresist 602 for processing.

[0095] In some embodiments, the micro / nano fabrication device 1 further includes a light source 200, a dichroic mirror 90, and an imaging module 100.

[0096] Light source 200 is used to emit illumination light onto the sample. The illumination light shines on the surface of sample 60, providing sufficient brightness for observation of the processed area.

[0097] During the processing, the two-photon initiator FO2 in the photoresist 602 is excited by a femtosecond pulsed laser to generate fluorescence. The wavelength of this fluorescence differs from that of the femtosecond pulsed laser; in this embodiment, the photoresist 602 generates fluorescence with a wavelength of 530 nm. For the emission direction of the fluorescence generated by the photoresist, a dichroic mirror 90 is simultaneously positioned in the emission light path of the fluorescence. Figure 1 The fluorescence exits from the low numerical aperture objective lens 40 and propagates in the opposite direction to the incident laser, reaching the dichroic mirror 90. The dichroic mirror 90 is wavelength selective, exhibiting high transmittance for 780nm femtosecond pulsed laser light but high reflectivity for 530nm fluorescence. Therefore, the dichroic mirror 90 reflects the 530nm fluorescence back to the optical path of the imaging module 100, thus achieving separation between the processing optical path and the monitoring optical path.

[0098] The imaging module 100 can be a CCD camera. The imaging module 100 is positioned in the transmission light path of the dichroic mirror 90 and is used to acquire processing images of the processing area. The curing state of the photoresist 602 can be observed through these images, allowing for real-time monitoring of the processing. When the power of the femtosecond pulsed laser exceeds a threshold, the photoresist 602 at the focal point will emit fluorescence after curing. This fluorescence appears as a bright spot in the acquired processing image, allowing the operator to determine the processing status of the micro / nano structure based on the presence and brightness of these bright spots.

[0099] Thus, through the cooperation of the light source 200, the dichroic mirror 90 and the imaging module 100, the micro-nano processing device 1 provided in this application embodiment can monitor the curing state of the photoresist 602 in real time during the processing. The operator can adjust the processing parameters in a timely manner according to the observed image, avoid processing failure due to parameter deviation, and improve the success rate and reliability of micro-nano processing.

[0100] In some embodiments, a second filter 300, a third reflector 1003, and a focusing lens 300 are further disposed between the dichroic mirror 90 and the imaging module 100.

[0101] The second filter 300 is disposed on the reflected light path of the dichroic mirror 90 and is located in the direction through which the fluorescence is transmitted. It is used to further filter out stray light in the fluorescence, especially any residual 780nm femtosecond pulsed laser light, to ensure the purity of the light signal entering the imaging module 100.

[0102] The third reflector 1003 is disposed on the light-emitting side of the second filter 300 to change the propagation direction of the fluorescence light path, making the light path layout more compact and facilitating the installation and debugging of the imaging module 100.

[0103] The focusing lens 300 is disposed on the light-emitting side of the third reflecting mirror 1003 to focus the fluorescent beam so that it can be clearly received by the imaging module 100.

[0104] The imaging module 100 is disposed on the light-emitting side of the focusing lens 300 and is used to acquire real-time images of the processing area. In some embodiments, the micro / nano fabrication device 1 further includes an aperture stop. The aperture stop is disposed between the dual telecentric optical module 80 and the low numerical aperture objective lens 40, that is, between the light-emitting side of the sleeve lens 802 and the light-incident side of the low numerical aperture objective lens 40.

[0105] An aperture is an optical element with a light-transmitting aperture, which controls the amount of light entering subsequent elements by limiting the cross-sectional area of ​​the light beam. In the embodiments of this application, the aperture is used to further eliminate stray light.

[0106] By setting an aperture stop, stray light can be blocked outside the stop, allowing only the femtosecond pulsed laser in the main optical path to pass through, thereby minimizing the aberrations of the low numerical aperture objective lens 40. At the same time, the aperture stop can also limit the aperture angle of the beam, further optimizing the beam quality entering the low numerical aperture objective lens 40, ensuring that the size and shape of the focused spot formed by the low numerical aperture objective lens 40 are closer to the ideal state.

[0107] The second aspect of this application provides a micro / nano fabrication method, which can be applied to the micro / nano fabrication apparatus 1 provided in the first aspect embodiment of this application. The micro / nano fabrication apparatus 1 may include a controller, which can be connected to a femtosecond laser source module 10, a beam adjustment module 20, a scanning module 30, and a motion platform 50, for controlling the coordinated operation of the above modules. The controller can be a computer, a microcontroller, a programmable logic controller, or other devices with data processing and control functions. Figure 4 As shown, this micro / nano fabrication method can be executed by a controller and includes the following steps: Step 401: Ensure that the sample containing photoresist is fixed on the motion platform.

[0108] Photoresist undergoes a polymerization reaction under subsequent laser irradiation, transforming from a liquid to a solid state to form micro / nano structures. The photoresist has a two-photon absorption cross-section ≥1000 GM at a preset wavelength. Operators can fix the sample on a motion platform, and the sample's position is precisely controlled by a controller via the motion platform.

[0109] Step 402: Turn on the laser source module and output femtosecond pulse laser. Perform beam shaping on the femtosecond pulse laser through the beam adjustment module.

[0110] The controller performs beam shaping processes such as beam expansion, filtering, and power adjustment on the femtosecond pulsed laser through the beam adjustment module, so that the beam diameter of the femtosecond pulsed laser matches the entrance pupil diameter of the subsequent objective lens, filters out unwanted wavelength components in the laser, and controls the power of the femtosecond pulsed laser at 2.2mW or above.

[0111] The controller adjusts the lens spacing of the beam expander by controlling the beam expander's drive mechanism, thereby changing the beam diameter of the femtosecond pulsed laser. This ensures that the expanded beam diameter matches the entrance pupil diameter of the subsequent low numerical aperture objective lens, guaranteeing that the numerical aperture of the objective lens can be fully utilized.

[0112] The first filter of the beam conditioning module is a 770-790nm bandpass filter, which can transmit femtosecond pulsed laser light of a preset wavelength and filter out the 1560nm fundamental frequency light remaining during the frequency doubling process. This process does not require active control by the controller; the first filter itself has wavelength selectivity, and the femtosecond pulsed laser completes the filtering process as it passes through the first filter.

[0113] The controller adjusts the attenuation of the femtosecond pulsed laser by controlling the rotation angle of the rotating beam attenuator, thereby continuously regulating the output laser power. Based on preset processing parameters, the controller keeps the femtosecond pulsed laser power within a range greater than or equal to 2.2mW, ensuring it meets the two-photon polymerization threshold power for the photoresist.

[0114] Step 403: In the current layer, the adjusted femtosecond pulse laser is controlled by the scanning module to scan in the XY plane according to the preset scanning path.

[0115] Before starting processing the current layer, the controller reads a pre-stored preset scan path file. This preset scan path file is generated by performing 2D slicing and layered scattering processing on the 3D model of the micro / nano structure. 2D slicing is the process of dividing the 3D model into a series of thin layers along the Z-axis, with each layer corresponding to a 2D graphic. Layered scattering processing converts the 2D graphic of each layer into a scan trajectory that the scanning module can recognize, i.e., the preset scan path. Therefore, the preset scan path file contains the graphic information to be processed for each layer, as well as the corresponding preset scan path for each layer.

[0116] The controller sends control signals to the scanning module based on the coordinate data in the preset scan path file. The scanning module then drives the scanning galvanometer to change its deflection angle accordingly, causing the focal point of the femtosecond pulsed laser to move along the preset scan path in the XY plane.

[0117] During the scanning process, wherever the laser focus is, the two-photon initiator FO2 in the photoresist absorbs the two-photon energy and initiates a polymerization reaction, causing the photoresist at that location to change from a liquid state to a solid state, thereby forming a two-dimensional pattern on the current layer corresponding to the preset scanning path.

[0118] The controller keeps the scanning speed within the range of 60μm / s to 70μm / s, so that the energy received by each exposure point just reaches the threshold condition, ensuring sufficient curing while keeping the curing area within a small range.

[0119] Step 404: After scanning the current layer, the sample is moved a distance of one layer thickness in the Z-axis direction by the motion platform and the scanning module is controlled to scan the next layer until all layers are scanned to obtain the micro-nano structure.

[0120] After scanning the current layer, the corresponding two-dimensional pattern has been solidified in the photoresist using laser scanning. To construct the three-dimensional structure, the next layer needs to be processed.

[0121] The controller sends control signals to the motion platform based on the layer thickness data specified in the preset scan path file. Upon receiving the control signals, the motion platform drives the sample to move precisely a distance equal to one layer thickness along the Z-axis. The Z-axis direction is perpendicular to the XY plane, which is the stacking direction of the processed structure. The layer thickness is a preset parameter, usually consistent with the layer thickness used in slicing, for example, 200 nm.

[0122] After the sample moves to the next layer, the controller reads the preset scan path for the next layer from the preset scan path file and sends a control signal to the scanning module. The scanning module then drives the scanning galvanometer to change its deflection angle according to the control signal, causing the focus of the femtosecond pulsed laser to move along the preset scan path for the next layer in the XY plane, thus completing the processing of the next layer.

[0123] The controller repeats the above layer-by-layer processing steps until all layers in the preset scan path file have been scanned. By stacking the two-dimensional patterns formed by each solidified layer, a three-dimensional micro / nano structure is finally obtained.

[0124] Then, the operator can immerse the micro-nano structure in the developing solution, clean it, and dry it to obtain a clean micro-nano structure.

[0125] During the layer-by-layer scanning process, the photoresist areas scanned by the laser focus undergo polymerization and solidify, while the photoresist in the remaining areas remains liquid. To obtain the complete micro / nano structure, these uncured photoresist areas need to be removed.

[0126] Therefore, the scanned sample can be immersed in a developing solution. The developing solution can dissolve the uncured photoresist, while the cured micro / nano structures are resistant to the developing solution and thus can be preserved. The developing time can be determined according to the type and thickness of the photoresist; for example, it can be 10 minutes.

[0127] After development, developer may remain on the sample surface, requiring further cleaning. Place the sample in a cleaning solution, such as isopropanol (IPA), and soak for a certain period to remove any residual developer. The cleaning time can be determined as needed, for example, 15 minutes.

[0128] Finally, the cleaned sample is removed and placed in a dry environment to air dry or dried using a drying device to remove the liquid from the sample surface, thus obtaining the final clean micro / nano structure.

[0129] In some embodiments, prior to step 401 or step 402, the micro / nano fabrication method further includes Step 405: Receive a 3D model of the micro / nano structure generated by 3D modeling software.

[0130] Operators use 3D modeling software to generate 3D models of the micro / nano structures. This software can be commercial applications such as Solidworks, AutoCAD, and 3ds Max, or open-source 3D modeling tools. Based on the shape, size, and structural features of the micro / nano structure to be fabricated, operators construct the corresponding 3D model in the software. The 3D model describes the geometric information of the micro / nano structure in three-dimensional space, including parameters such as the contour, height, aperture, and line width of each layer.

[0131] Step 406: Perform 2D slicing and layered scattering processing on the 3D model to generate a preset scan path containing the scan pattern of each layer.

[0132] The controller can perform 2D slicing on the 3D model. 2D slicing is the process of dividing the 3D model into a series of thin layers along the Z-axis. The thickness of each layer is the layer thickness in subsequent processing, and the layer thickness can be set according to the processing accuracy requirements, for example, it can be 200nm. After the slicing process is completed, a corresponding 2D graphic is generated for each layer, which is the contour that needs to be processed for that layer.

[0133] The controller performs layered scattering processing on the 2D graphics generated from the slices. Layered scattering processing converts the 2D graphics of each layer into a scanning trajectory that the scanning module 30 can recognize. The scanning trajectory generated by layered scattering processing is the preset scanning path, which contains information such as the movement trajectory of the laser focus in each layer, the scanning sequence, and the scanning speed.

[0134] The controller stores the generated preset scan path file in its storage unit. This preset scan path file is used in subsequent step 403, and the controller uses this file to control the scanning module to perform layer-by-layer scanning during the processing.

[0135] like Figure 5 As shown, micro-nano structures are fabricated using the micro-nano fabrication apparatus 1 and method provided in any of the above embodiments of this application. The fabrication results are observed and measured using a scanning electron microscope. The results show that the minimum fabrication linewidth of the fabricated micro-nano structures can be less than 80 nm, and the maximum lateral spatial resolution can reach 76 nm.

[0136] Specifically, micro- and nanostructures were fabricated under the following conditions: femtosecond pulsed laser wavelength of 780 nm, pulse width of 120 fs, repetition rate of 100 MHz, laser power of 2.2 mW, and scanning speed of 60 μm / s to 70 μm / s. The two-photon initiator FO2 used in the photoresist 602 has a two-photon absorption cross-section of 1184 GM at 780 nm, and the numerical aperture NA of the low numerical aperture objective lens 40 is 0.4. The fabrication results were observed and measured using a scanning electron microscope. The results showed that the fabricated linewidth of the micro- and nanostructures could be less than 80 nm, and the maximum lateral spatial resolution could reach 76 nm. The finest fabricated linewidth could reach below 62 nm, indicating that the micro- and nanostructure fabrication apparatus 1 and the micro- and nanostructure fabrication method provided in this application embodiment can achieve high fabrication accuracy.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A micro / nano fabrication device, characterized in that, include: Laser source module, used to output femtosecond pulsed laser; A beam shaping module is located on the light-emitting side of the laser source module and is used to perform beam shaping processing on the femtosecond pulse laser. A scanning module, located on the light-emitting side of the beam adjustment module, is used to control the femtosecond pulsed laser to scan in the XY plane; A low numerical aperture objective lens is disposed on the light-emitting side of the scanning module to focus the scanned femtosecond pulse laser. The numerical aperture NA of the low numerical aperture objective lens satisfies: 0.3≤NA≤0.

7. A motion platform is used to carry the sample and control the movement of the sample in the Z-axis direction. The sample includes photoresist. The femtosecond pulsed laser, after being focused, converges to the photoresist, triggering a two-photon polymerization reaction in the photoresist. The cured photoresist forms a micro-nano structure. The two-photon absorption cross section of the photoresist at a preset wavelength is ≥1000GM.

2. The micro / nano fabrication device according to claim 1, characterized in that, The laser source module includes: A laser, wherein the laser uses erbium-doped fiber as the gain medium and is used to output femtosecond pulse seed light with a wavelength of λ1, wherein λ1 satisfies: 1540nm≤λ1≤1580nm; A frequency doubling crystal is disposed on the light-emitting side of the laser to frequency double the femtosecond pulse seed light into a femtosecond pulse laser with a preset wavelength λ2, wherein λ2 satisfies: 770nm≤λ2≤790nm.

3. The micro / nano fabrication device according to claim 2, characterized in that, The femtosecond pulsed laser output by the frequency doubling crystal has a pulse width of <120fs, a repetition frequency of 100±1MHz, a maximum output power of >100mW, a peak power of >1.8kW, and a beam quality factor M² <1.

2.

4. The micro / nano fabrication apparatus according to claim 1, characterized in that, The beam adjustment module includes: A beam expander is used to increase the beam diameter of the femtosecond pulsed laser so that the beam diameter of the expanded femtosecond pulsed laser matches the entrance pupil diameter of the low numerical aperture objective lens. A rotating beam attenuator is located on the output side of the beam expander. The rotating beam attenuator is used to continuously adjust the power P of the femtosecond pulsed laser to adjust the power of the femtosecond pulsed laser to be greater than or equal to the threshold power of the two-photon polymerization reaction of the photoresist. The power P of the femtosecond pulsed laser is ≥2.2mW.

5. The micro / nano fabrication apparatus according to claim 1, characterized in that, The scanning module includes: A scanning galvanometer is used to control the femtosecond pulsed laser to scan in the XY plane. The scanning range D of the XY plane of the scanning galvanometer satisfies: 180μm≤D≤220μm.

6. The micro / nano fabrication apparatus according to any one of claims 1 to 5, characterized in that, The micro / nano fabrication device also includes: A dual telecentric optical module is disposed between the scanning module and the low numerical aperture objective lens. The dual telecentric optical module is used to collimate and eliminate aberrations of the beam output by the scanning module so that the femtosecond pulse laser is perpendicularly incident on the low numerical aperture objective lens.

7. The micro / nano fabrication apparatus according to claim 6, characterized in that, The dual telecentric optical module includes: A scanning lens, used to converge the femtosecond pulse laser output from the scanning module; A sleeve lens is disposed on the light-emitting side of the scanning lens, and the sleeve lens is used to collimate the light beam converged by the scanning lens into parallel light for emission.

8. The micro / nano fabrication apparatus according to claim 1, characterized in that, The micro / nano fabrication device also includes: A light source for emitting illumination light onto the sample; A dichroic mirror is disposed on the light-incident side of the low numerical aperture objective lens to transmit the fluorescence generated by the photoresist. An imaging module is disposed on the reflected light path of the dichroic mirror and is used to acquire the processed image of the processed area of ​​the sample.

9. The micro / nano fabrication apparatus according to any one of claims 1 to 5, characterized in that, The wavelength λ2 of the femtosecond pulsed laser output by the beam adjustment module satisfies: 770nm ≤ λ2 ≤ 790nm; and / or The beam adjustment module adjusts the power P of the femtosecond pulsed laser to ≥2.2mW; and / or The scanning module adjusts the scanning speed of the femtosecond pulse laser to 60μm / s≤v≤70μm / s; and / or The fabrication linewidth of the micro / nano structure is ≤80nm.

10. A micro / nano fabrication method, characterized in that, The micro / nano fabrication method includes: The sample containing photoresist is fixed on a motion platform, and the photoresist has a two-photon absorption cross section ≥1000GM at a preset wavelength; The laser source module is turned on and a femtosecond pulse laser is output. The femtosecond pulse laser is then shaped by the beam adjustment module. In the current layer, the adjusted femtosecond pulse laser is controlled by the scanning module to scan in the XY plane according to a preset scanning path; After scanning the current layer, the motion platform controls the sample to move a distance of one layer thickness in the Z-axis direction and controls the scanning module to scan the next layer until all layers are scanned to obtain the micro / nano structure.

Images