A system and method for preparing a double-ring structure in one step based on laser direct writing

Abstract

The present invention discloses a system and method for fabricating a double-ring structure in one step based on laser direct writing. The system includes a continuous laser, a beam expansion system, an attenuation plate, a half-wave plate, an optical shutter, a spectrometer, an oil-immersion objective lens, and a positive-negative adjustable photoresist sample arranged along an optical path; further includes a three-dimensional high-precision nanopositioning translation stage, a lens, a CCD camera, and a computer; the spectrometer focuses an incident continuous-wave laser beam onto the surface of the positive-negative adjustable photoresist sample via the oil-immersion objective lens, and a portion of the laser beam incident on the sample surface is reflected back onto the spectrometer and then irradiated onto a third lens; the oil-immersion objective lens focuses the laser beam onto the sample, thereby fabricating the double-ring structure in one step. The present invention can obtain the double-ring structure in one step through a single process at a lower cost, rather than through two or more cumbersome steps; and the inner and outer diameters of the desired double-ring structure can be flexibly changed by changing the power density and the direct writing time.

Description

Technical Field

[0001] The present invention relates to the technical field of laser direct writing, and in particular to a system and method for preparing a double-ring structure in one step based on laser direct writing. Background Art

[0002] With the rapid development of nano / micro technologies, there is a huge demand for multi-purpose submicron photonic structures, such as diffraction gratings, resonant cavities, photonic crystals, and plasmonic structures. Compared with other lithography techniques, laser direct writing (DLW) technology has been widely used in the field of nano / micro manufacturing to prepare 1D, 2D, and 3D photonic structures due to its ease of integration, submicron resolution, and maskless operation. Unfortunately, the limitations of organic photoresists (only positive or negative photoresists can be selected in a single process) and the associated operating environment have hindered traditional DLW methods.

[0003] The recently developed low single-photon absorption (LSP) DLW method offers the ability to combine single-photon (SP) and two-photon (or) multi-photon (TP) methods. This method relies on the wavelength of the excitation laser being close to the absorption band edge of the photoresist. One can create the desired submicron structure by changing the wavelength, numerical aperture, and photoresist. However, this method cannot solve the multi-step and complex sample fabrication process. Recently, Tong et al. used positive organic photoresist S1805 / 1818 to prepare 2D and 3D polymer structures by DLW through photoinduced local heating effect and various post-lithography processes to convert the material to negative. However, the problem is that it is difficult to remove the cross-linked polymer, which leads to the instability of the prepared 3D patterns. They claimed that the polymer curing is caused by cross-linking at the polymer / glass transition temperature. This phenomenon has been described for a long time, but the exact mechanism remains unknown. Therefore, the application of this technology is questionable. In addition, Xi et al. reported an inorganic photoresist Ge2Sb 1.5 Bi 0.5 Research on laser-induced phase transitions in Te5 shows that this photoresist exhibits both positive and negative modulation depending on laser intensity. However, its use as a template or host material in DLW techniques is not ideal. Each system has its own limitations and mechanisms that must be addressed.

[0004] Furthermore, Lim et al. utilized a combined UV lithography and DLW method, using both positive and negative organic photoresists to fabricate the desired patterns with good resolution and fabrication efficiency. However, the complex instrumentation and mask-assisted processes make this technique impractical. Typically, only one type of photoresist, either positive or negative, is available, requiring a very complex processing / experimental procedure if we want to combine both properties while fabricating versatile photonic structures. Because organic photoresists easily combine with guest materials and flexible templates, they are ideal for fabricating diverse polymer structures. Therefore, developing suitable techniques is essential, rather than searching for new photoresists. This problem persists due to a lack of knowledge about the interaction between LSP-DLW and available organic photoresists. Moreover, most studies described to date, including details of the multi-step preparation of one-dimensional, two-dimensional, and three-dimensional polymer structures, have not acknowledged their practicality and flexibility.

[0005] Due to their enormous research potential in fields such as micron and submicron-scale double-ring and concentric-ring structures, their fabrication has gradually attracted the attention of researchers. Currently, the main methods for fabricating double-ring and concentric-ring structures include etching, mask-assisted fabrication, and femtosecond / nanosecond laser pulse induction. Etching, a common method in micro-nanofabrication, primarily involves stripping and removing material through solutions, reactive ions, or other mechanical means to accurately replicate the mask pattern. However, this method requires expensive etching equipment and demanding etching conditions, making it difficult to obtain high-quality double-ring structures. Mask-assisted fabrication uses prefabricated masks to assist in the fabrication of the desired structure. However, the complex mask preparation process makes it difficult to obtain, and a single template can only produce structures with a single parameter, failing to meet the requirements of multiple parameters. Femtosecond / nanosecond laser pulse induction requires expensive femtosecond / nanosecond lasers, resulting in high fabrication costs. Summary of the Invention

[0006] In view of this, in order to solve the problem in the prior art that the double-ring structure needs to be obtained through two or more processing steps or the preparation method is too costly, the present invention proposes a system and method for preparing a double-ring structure in one step based on laser direct writing.

[0007] The present invention solves the above problems through the following technical means:

[0008] In one aspect, the present invention provides a system for fabricating a double-ring structure in one step based on laser direct writing, comprising a continuous laser, a beam expansion system, an attenuation plate, a half-wave plate, an optical shutter, a spectrometer, an oil-immersion objective lens, and a positive-negative adjustable photoresist sample arranged along an optical path; the system also comprises a three-dimensional high-precision nanopositioning translation stage, a third lens, a CCD camera, and a computer;

[0009] The positive and negative adjustable photoresist sample is mounted on a three-dimensional high-precision nanopositioning translation stage;

[0010] The continuous laser is used to emit a continuous wave laser beam;

[0011] The beam expansion system is used to expand the continuous wave laser beam;

[0012] The attenuation plate is used to control the energy of the continuous wave laser beam after beam expansion;

[0013] The half-wave plate is used to control the polarization direction of the continuous wave laser beam;

[0014] The optical shutter is used to control the light flux of the continuous wave laser beam;

[0015] The spectroscopic device is used to focus the incident continuous wave laser beam onto the surface of the positive and negative adjustable photoresist sample through the oil immersion objective lens, and a part of the laser incident on the surface of the positive and negative adjustable photoresist sample is reflected onto the spectroscopic device and then irradiated onto the third lens;

[0016] The oil immersion objective lens is used to focus the laser beam on the positive and negative adjustable photoresist sample, to prepare the double ring structure in one step, and then to develop it with a developer;

[0017] The third lens is used to focus the laser beam on the CCD camera;

[0018] The CCD camera is used to monitor the processing process in real time and observe the exposure of the light beam;

[0019] The computer is used to control the three-dimensional high-precision nanopositioning translation stage and the CCD camera.

[0020] Preferably, the beam expansion system comprises a first lens and a second lens arranged along the optical path; the continuous wave laser beam is expanded by passing through the first lens and the second lens in sequence.

[0021] Preferably, the system for preparing a double-ring structure in one step based on laser direct writing further includes a first reflector and a second reflector arranged along the optical path; the expanded continuous wave laser beam is sequentially emitted to the attenuation plate through the first reflector and the second reflector.

[0022] Preferably, the positive-negative tunable photoresist sample includes a substrate and an S1813 positive photoresist coated on the substrate.

[0023] Preferably, the S1813 positive photoresist comprises cresol novolac resin, diazonaphthoquinone photosensitive compound and solvent.

[0024] Preferably, the positive and negative tunable photoresist sample preparation process is as follows:

[0025] Before the spin coating process, the substrate was ultrasonically cleaned with acetone, ethanol, and methanol, and tiny particles were removed by dry inert gas. S1813 positive photoresist was spin-coated on the substrate at 500 rpm for 9 seconds and then at 5000 rpm for 60 seconds. The coated film was then gently baked at 115°C for 60 seconds. The final sample film thickness was 1.2 μm.

[0026] Preferably, the double-annular structure includes the following parts: A: the central part of the tightly focused light beam, where the solidified polymer is ablated; N: the outer part of the tightly focused light beam, where the positive photoresist is converted to negative, causing the polymer to solidify; P: the extreme outer part of the focused light beam, where normal polymerization reaction occurs and will be removed in the subsequent development process; U: the non-focused part, where the polymer film is not affected.

[0027] Preferably, the system for preparing a double-ring structure in one step based on laser direct writing can flexibly change the inner and outer diameters of the required double-ring structure by changing the power density and the direct writing time.

[0028] As a preferred method, the principle of preparing the double ring structure in one step is as follows:

[0029] The selected laser wavelength and power at the edge of the photoresist absorption region result in different intensities in different areas of the light spot. These intensities cause the corresponding areas to undergo no reaction, chemical conversion, and ablation, respectively, thereby producing the double-ring structure shown. Specifically, the applied laser beam can simultaneously produce ablation, negative, positive, and unexposed features in the polymer film. At this time, in the central part of the tightly focused beam, the solidified polymer is ablated. In the outer part of the tightly focused beam, the positive photoresist is converted to negative, causing the polymer to solidify. At the extreme outside of the focused beam, a normal polymerization reaction occurs and is removed in the subsequent development process. In the non-focused part, the polymer film is unaffected.

[0030] In another aspect, the present invention provides a method for preparing a double-ring structure in one step based on laser direct writing, comprising the following steps:

[0031] The positive and negative adjustable photoresist sample is mounted on a three-dimensional high-precision nanopositioning translation stage;

[0032] A continuous wave laser beam is emitted by a continuous laser;

[0033] A beam expansion system is used to expand the continuous wave laser beam;

[0034] An attenuator is used to control the energy of the continuous wave laser beam after beam expansion;

[0035] A half-wave plate is used to control the polarization direction of the continuous wave laser beam;

[0036] An optical shutter is used to control the light flux of a continuous wave laser beam;

[0037] A beam splitter or polarization beam splitter prism is used to focus the incident continuous wave laser beam onto the surface of the positive and negative adjustable photoresist sample through an oil immersion objective lens. A portion of the laser beam incident on the surface of the positive and negative adjustable photoresist sample is reflected onto the beam splitter or polarization beam splitter prism and then irradiated onto the third lens.

[0038] An oil-immersion objective is used to focus a laser beam on a positive-negative tunable photoresist sample, creating a double-ring structure in one step, which is then developed using a developer. The principle is as follows: the laser wavelength and power selected at the edge of the photoresist absorption region result in different intensities in different areas of the light spot. These intensities cause the corresponding areas to undergo no reaction, chemical conversion, and ablation, respectively, thereby producing the double-ring structure shown. Specifically, the applied laser beam can simultaneously produce ablation, negative, positive, and unexposed features in the polymer film. At this time, in the central part of the tightly focused beam, the solidified polymer is ablated. In the outer part of the tightly focused beam, the positive photoresist is converted to negative, causing the polymer to solidify. In the extreme outer part of the focused beam, a normal polymerization reaction occurs and is removed in the subsequent development process. In the non-focused part, the polymer film is unaffected.

[0039] A third lens is used to focus the laser beam onto the CCD camera;

[0040] Use CCD camera to monitor the processing process in real time and observe the exposure of the light beam;

[0041] Computer-controlled three-dimensional high-precision nanopositioning translation stage and CCD camera.

[0042] Compared with the prior art, the beneficial effects of the present invention include at least:

[0043] The present invention can produce a double ring structure in a single process at a lower cost, rather than through two or more cumbersome steps. In addition, the method can flexibly change the inner and outer diameters of the desired double ring structure by changing the power density and direct writing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 12. It is a schematic structural diagram of a system for preparing a double-ring structure in one step based on laser direct writing according to the present invention;

[0046] Figure 2 This is the SEM image of the double ring structure of the present invention, where (a) the direct writing power density is 0.64mJ / μm 2 , under the condition of exposure time 0.05s, the double ring structure shown is formed by one step of processing; (b) the direct writing power density is 4.46mJ / μm 2 , the double ring structure shown is formed by one step of processing at a time under the condition of exposure time 0.1s;

[0047] Figure 3 It is a schematic diagram of the principle of the double ring structure of the present invention;

[0048] Figure 4 This is a flow chart of the method for preparing a double ring structure in one step based on laser direct writing according to the present invention.

[0049] Description of reference numerals:

[0050] 1. Continuous laser; 2. First lens; 3. Second lens; 4. First reflector; 5. Second reflector; 6. Attenuation plate; 7. Half-wave plate; 8. Optical shutter; 9. Spectral splitter; 10. Oil-immersion objective; 11. Three-dimensional high-precision nanopositioning translation stage; 12. Positive and negative adjustable photoresist sample; 13. Third lens; 14. CCD camera; 15. Computer. DETAILED DESCRIPTION

[0051] To make the above-mentioned objectives, features, and advantages of the present invention more clearly understood, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0052] Example 1

[0053] like Figure 1 As shown, the present invention provides a system for preparing a double-ring structure in one step based on laser direct writing, comprising a continuous laser 1, a beam expansion system, an attenuation plate 6, a half-wave plate 7, an optical shutter 8, a spectrometer 9, an oil-immersion objective lens 10, and a positive-negative adjustable photoresist sample 12 arranged along the optical path; further comprising a three-dimensional high-precision nanopositioning translation stage 11, a third lens 13, a CCD camera 14, and a computer 15;

[0054] The positive and negative adjustable photoresist sample 12 is mounted on a three-dimensional high-precision nanopositioning translation stage 11;

[0055] The continuous laser 1 is used to emit a continuous wave laser beam;

[0056] The beam expansion system is used to expand the continuous wave laser beam;

[0057] The attenuation plate 6 is used to control the energy of the continuous wave laser beam after beam expansion;

[0058] The half-wave plate 7 is used to control the polarization direction of the continuous wave laser beam;

[0059] The optical shutter 8 is used to control the light flux of the continuous wave laser beam;

[0060] The spectroscopic device 9 is used to focus the incident continuous wave laser beam onto the surface of the positive and negative tunable photoresist sample 12 through the oil immersion objective lens 10. A portion of the laser light incident on the surface of the positive and negative tunable photoresist sample 12 is reflected onto the spectroscopic device 9 and then irradiated onto the third lens 13. In this embodiment, the spectroscopic device 9 is a beam splitter or a polarization spectroscopic prism.

[0061] The oil immersion objective lens 10 is used to focus the laser beam on the positive and negative adjustable photoresist sample 12, to prepare a double ring structure in one step, and then to develop it with a developer;

[0062] The third lens 13 is used to focus the laser beam onto the CCD camera 14;

[0063] The CCD camera 14 is used to monitor the processing process in real time and observe the exposure of the light beam;

[0064] The computer 15 is used to control the three-dimensional high-precision nanopositioning translation stage 11 and the CCD camera 14 .

[0065] Specifically, the beam expansion system includes a first lens 2 and a second lens 3 arranged along the optical path; the continuous wave laser beam is expanded by passing through the first lens 2 and the second lens 3 in sequence.

[0066] Specifically, the system for preparing a double-ring structure in one step based on laser direct writing also includes a first reflector 4 and a second reflector 5 arranged along the optical path; the expanded continuous wave laser beam is emitted to the attenuation plate 6 through the first reflector 4 and the second reflector 5 in sequence.

[0067] Specifically, the positive-negative tunable photoresist sample 12 includes a substrate and S1813 positive photoresist coated on the substrate. The S1813 positive photoresist (Micorchem, USA) is composed of cresol novolac resin (NR), diazonaphthoquinone (DNQ) photosensitive compound and solvent.

[0068] Based on the single low-photon absorption mechanism, the present invention selects a continuous wave band (CW) laser with a wavelength of 473nm (located at the edge of the absorption area of ​​the photoresist S1813) as the irradiation source to directly write the positive photoresist S1813. In the experiment, an attenuator and a half-wave plate 7 are used to control the energy and polarization direction of the laser beam, and a 100x oil-immersion objective lens 10 (NA=1.4, Zeiss) is used to focus the laser beam on the sample 12. The sample 12 is mounted on a three-dimensional high-precision nanopositioning translation stage 11 (P-563, PI) controlled by a computer 15. The double ring structure can be prepared under the conditions of appropriate laser flux and exposure time. After direct writing, the sample 12 needs to be developed with MF319 developer for 30 seconds.

[0069] The principle behind the creation of the double-ring structure shown can be explained by the selection of laser wavelength (low single-photon absorption) and power at the edge of the photoresist's absorption region, resulting in different intensities in different areas of the spot. These intensities result in non-reaction, chemical conversion, and ablation in the corresponding areas, respectively. This results in the creation of the double-ring structure shown. Specifically, the applied laser beam can simultaneously create ablated, negative, positive, and unexposed features in the polymer film. In this case, in the central portion of the tightly focused beam, the solidified polymer is ablated; in the outer portion of the tightly focused beam, the positive photoresist is converted to negative, resulting in the solidification of the polymer; in the extreme outer portion of the focused beam, normal polymerization occurs (removed during subsequent development); and in the non-focused portion, the polymer film is unaffected.

[0070] According to the results of physical and chemical analysis, the positive S1813 photoresist is composed of NR and photoactive DNQ. The molecular structure of the cresol novolac polymer resin contains a large number of -OH groups, exhibiting strong hydrophilic properties and being easily dissolved by alkaline aqueous solutions. On the other hand, the photoactive DNQ is highly hydrophobic and exhibits anti-dissolution properties in alkaline / aqueous media. When DNQ is impregnated into the NR, the NR becomes hydrophobic, and its solubility is greatly suppressed. As a result, we obtain an insoluble film during spin coating / baking. When the polymer film is exposed to light, the water-insoluble photoactive chemical (DNQ) is converted into soluble indolecarboxylic acid (ICA), which helps dissolve the polymer resin in specific areas exposed to light. It can later be developed / removed using the corresponding developer / removal solution.

[0071] The conversion of DNQ to ICA is relatively poor when the incident light wavelength is close to the edge of the DNQ absorption band (hν to Eg). Furthermore, the diffusion kinetics of light in the polymer medium are not even in the exposure region of low absorption wavelengths. While increasing exposure time and light intensity, photothermal / ablative effects play a significant role. Furthermore, by varying exposure time and laser intensity, the diffusion rate of the newly converted ICA can be controlled. During the initial phase of light absorption, we believe two distinct phenomena occur simultaneously: (i) a significant amount of DNQ is converted to ICA, and (ii) a smaller amount of the converted ICA undergoes further structural changes through decarboxylation. Decarboxylated indanediones / indanedione dimers are hydrophobic, so they again act as dissolution inhibitors. Therefore, they help resist the polymer resin from the developer / solvent. Using a specific light intensity and a tightly focused spot at 473 nm to reach the threshold energy for the photochemical conversion of ICA / NR, negative photoresist behavior is observed. Meanwhile, the (loosely focused) threshold energy of the external beam is just sufficient to convert DNQ / NR to ICA / NR, during which positive photoresist behavior is observed. Furthermore, the unexposed areas form a polymer film, so complex patterns can be revealed in a single exposure.

[0072] At the laser flux (4.46 mJ μm -2 ) and exposure time (0.1s), it is formed by one step of processing Figure 2 (b) shows the ring structure. In this case, the applied laser beam can simultaneously generate ablated, negative, positive, and unexposed features in the polymer film. Thus, in the central portion of the tightly focused beam, the cured polymer (formed by the negative behavior of S1813) is ablated; in the outer portion of the tightly focused beam, the positive is converted to the negative (causing the polymer to cure); in the extreme outer portion of the focused beam, the DNQ is converted to ICA (causing positive behavior); and in the unfocused portion, the polymer film is unaffected.

[0073] Typically, this dual-ring structure requires two or more processing steps or is too expensive to produce. However, the present invention enables this structure to be produced in a single, low-cost process. Furthermore, this method allows for the flexible adjustment of the inner and outer diameters of the desired dual-ring structure by varying the power density and direct writing time.

[0074] The system preparation process of the present invention for preparing a double-ring structure in one step based on laser direct writing is generally as follows:

[0075] Materials: S1813 positive photoresist (Micorchem, USA) consists of cresol novolac resin (NR), diazonaphthoquinone (DNQ) photosensitive compound, and solvent. MF319 developer (N-methylpyrrolidone (NMP)) was purchased from Resmi Co., Ltd. The photoresist and NMP solution were prepared by diluting with MilliQ water (18.2 MΩ·cm).

[0076] 2. Sample Preparation: Prior to the spin coating process, the substrate was ultrasonically cleaned with acetone, ethanol, and methanol, and fine particles were removed by drying with inert gas. S1813 was spin-coated on a glass substrate at 500 rpm for 9 seconds, followed by 5000 rpm for 60 seconds. The coated film was then gently baked at 115°C for 60 seconds. The final film thickness of Sample 12 was 1.2 μm.

[0077] 3. Preparation process: As shown in Figure 1, a continuous wave (CW) laser with a wavelength of 473nm is used as the irradiation source. In order to control the energy and polarization direction of the laser beam, an attenuation plate 6 and a half-wave plate 7 are used. A 100x oil-immersion objective lens 10 (NA=1.4, Zeiss) is used to focus the laser beam on the sample 12. The sample 12 is mounted on a three-dimensional high-precision nanopositioning translation stage 11 (P-563, PI) controlled by a computer 15. The double ring structure can be prepared under the conditions of appropriate laser flux and exposure time. After direct writing, the sample 12 needs to be developed with MF319 developer for 30 seconds.

[0078] Figure 2 This is the SEM image of the double ring structure of the present invention, where (a) the direct writing power density is 0.64mJ / μm 2 , under the condition of exposure time 0.05s, the double ring structure shown is formed by one step of processing; (b) the direct writing power density is 4.46mJ / μm 2 Under the condition of exposure time of 0.1s, the double ring structure shown is formed by one step of processing at a time; it can be seen that the present invention can flexibly change the inner and outer diameters of the required double ring structure by changing the power density and direct writing time.

[0079] like Figure 3 As shown, the double-ring structure includes the following parts: A: the central part of the tightly focused light beam, where the solidified polymer is ablated; N: the outer part of the tightly focused light beam, where the positive photoresist is converted to negative, causing the polymer to solidify; P: the extreme outer part of the focused light beam, where normal polymerization occurs and will be removed in the subsequent development process; U: the non-focused part, where the polymer film is not affected.

[0080] Example 2

[0081] like Figure 4 As shown, the present invention provides a method for preparing a double ring structure in one step based on laser direct writing, comprising the following steps:

[0082] S1, mounting the positive and negative adjustable photoresist sample 12 on the three-dimensional high-precision nanopositioning translation stage 11;

[0083] S2, using continuous laser 1 to emit a continuous wave laser beam;

[0084] S3, using a beam expansion system to expand the continuous wave laser beam;

[0085] S4, using an attenuation plate 6 to control the energy of the continuous wave laser beam after beam expansion;

[0086] S5, using a half-wave plate 7 to control the polarization direction of the continuous wave laser beam;

[0087] S6, using the optical shutter 8 to control the light flux of the continuous wave laser beam;

[0088] S7, using a beam splitter or polarization beam splitter prism 9 to focus the incident continuous wave laser beam onto the surface of the positive and negative adjustable photoresist sample 12 through the oil immersion objective lens 10, and a portion of the laser beam incident on the surface of the positive and negative adjustable photoresist sample 12 is reflected onto the beam splitting device 9 and then irradiated onto the third lens 13;

[0089] S8. Using an oil-immersion objective lens 10, the laser beam is focused on a positive-negative tunable photoresist sample 12 to prepare a double-ring structure in one step, which is then developed using a developer. The principle is as follows: the laser wavelength and power selected at the edge of the photoresist absorption region are such that different areas of the light spot have different intensities, which respectively cause the corresponding areas to be unreactive, chemically converted, and ablated, thereby producing the double-ring structure shown. Specifically, the applied laser beam can simultaneously produce ablation, negative, positive, and unexposed features in the polymer film. At this time, in the center of the tightly focused beam, the solidified polymer is ablated. In the outer part of the tightly focused beam, the positive photoresist is converted to negative, resulting in the solidification of the polymer. In the extreme outer part of the focused beam, a normal polymerization reaction occurs and is removed in the subsequent development process. In the non-focused part, the polymer film is unaffected.

[0090] S9, using the third lens 13 to focus the laser beam onto the CCD camera 14;

[0091] S10, using a CCD camera 14 to monitor the processing process in real time and observe the exposure of the light beam;

[0092] S11 , using the computer 15 to control the three-dimensional high-precision nanopositioning translation stage 11 and the CCD camera 14 .

[0093] The process of the present invention for preparing a double-ring structure in one step based on laser direct writing generally includes the following steps:

[0094] Materials: S1813 positive photoresist (Micorchem, USA) consists of cresol novolac resin (NR), diazonaphthoquinone (DNQ) photosensitive compound, and solvent. MF319 developer (N-methylpyrrolidone (NMP)) was purchased from Resmi Co., Ltd. The photoresist and NMP solution were prepared by diluting with MilliQ water (18.2 MΩ·cm).

[0095] 2. Sample Preparation: Prior to the spin coating process, the substrate was ultrasonically cleaned with acetone, ethanol, and methanol, and fine particles were removed by drying with inert gas. S1813 was spin-coated on a glass substrate at 500 rpm for 9 seconds, followed by 5000 rpm for 60 seconds. The coated film was then gently baked at 115°C for 60 seconds. The final film thickness of Sample 12 was 1.2 μm.

[0096] 3. Preparation process: As shown in the figure, a continuous wave (CW) laser with a wavelength of 473 nm is used as the irradiation source. In order to control the energy and polarization direction of the laser beam, an attenuation plate 6 and a half-wave plate 7 are used. The laser beam is focused on the sample 12 using a 100x oil immersion objective lens 10 (NA=1.4, Zeiss). The sample 12 is mounted on a three-dimensional high-precision nanopositioning translation stage 11 (P-563, PI) controlled by a computer 15. Under appropriate laser flux and exposure time conditions (such as Figure 2 After direct writing, sample 12 was developed with MF319 developer for 30 seconds.

[0097] The other features of this embodiment are the same as those of embodiment 1, so they will not be repeated here.

[0098] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A system for preparing a double ring structure in one step based on laser direct writing, characterized in that: It includes a continuous laser, a beam expansion system, an attenuation plate, a half-wave plate, an optical shutter, a spectrometer, an oil-immersion objective lens, and a positive and negative adjustable photoresist sample arranged along the optical path; it also includes a three-dimensional high-precision nanopositioning translation stage, a third lens, a CCD camera, and a computer; The positive and negative adjustable photoresist sample is mounted on a three-dimensional high-precision nanopositioning translation stage; the positive and negative adjustable photoresist sample comprises a substrate and an S1813 positive photoresist coated on the substrate; the S1813 positive photoresist comprises a cresol novolac resin, a diazonaphthoquinone photosensitive compound and a solvent; The continuous laser is used to emit a continuous wave laser beam; The beam expansion system is used to expand the continuous wave laser beam; The attenuation plate is used to control the energy of the continuous wave laser beam after beam expansion; The half-wave plate is used to control the polarization direction of the continuous wave laser beam; The optical shutter is used to control the light flux of the continuous wave laser beam; The spectroscopic device is used to focus the incident continuous wave laser beam onto the surface of the positive and negative adjustable photoresist sample through the oil immersion objective lens, and a part of the laser incident on the surface of the positive and negative adjustable photoresist sample is reflected onto the spectroscopic device and then irradiated onto the third lens; The oil immersion objective lens is used to focus the laser beam on the positive and negative adjustable photoresist sample, to prepare the double ring structure in one step, and then to develop it with a developer; The third lens is used to focus the laser beam on the CCD camera; The CCD camera is used to monitor the processing process in real time and observe the exposure of the light beam; The computer is used to control the three-dimensional high-precision nanopositioning translation stage and the CCD camera; The principle of preparing the double ring structure in one step is as follows: The selected laser wavelength and power at the edge of the photoresist absorption region result in different intensities in different areas of the light spot. These intensities cause the corresponding areas to undergo no reaction, chemical conversion, and ablation, respectively, thereby producing the double-ring structure shown. Specifically, the applied laser beam can simultaneously produce ablation, negative, positive, and unexposed features in the polymer film. At this time, in the central part of the tightly focused beam, the solidified polymer is ablated. In the outer part of the tightly focused beam, the positive photoresist is converted to negative, causing the polymer to solidify. At the extreme outside of the focused beam, a normal polymerization reaction occurs and is removed in the subsequent development process. In the non-focused part, the polymer film is unaffected.

2. The system for preparing a double ring structure in one step based on laser direct writing according to claim 1, characterized in that: The beam expansion system comprises a first lens and a second lens arranged along the optical path; the continuous wave laser beam is expanded by sequentially passing through the first lens and the second lens.

3. The system for preparing a double ring structure in one step based on laser direct writing according to claim 1, characterized in that: The system for preparing a double-ring structure in one step based on laser direct writing further includes a first reflector and a second reflector arranged along the optical path; the expanded continuous wave laser beam is sequentially emitted to the attenuation plate through the first reflector and the second reflector.

4. The system for preparing a double ring structure in one step based on laser direct writing according to claim 1, characterized in that: The positive and negative adjustable photoresist sample preparation process is as follows: Before the spin coating process, the substrate was ultrasonically cleaned with acetone, ethanol, and methanol, and tiny particles were removed by dry inert gas. S1813 positive photoresist was spin-coated on the substrate at 500 rpm for 9 seconds and then at 5000 rpm for 60 seconds. The coated film was then gently baked at 115°C for 60 seconds. The final sample film thickness was 1.2 μm.

5. The system for preparing a double ring structure in one step based on laser direct writing according to claim 1, characterized in that: The double-annular structure includes the following parts: A: the central part of the tightly focused beam, where the solidified polymer is ablated; N: The outer part of the tightly focused beam, where the photoresist converts from positive to negative, causing the polymer to solidify; P: The extreme outer part of the focused beam, where normal polymerization occurs and is removed during subsequent development. U: Non-focused area, where the polymer film is not affected.

6. The system for preparing a double ring structure in one step based on laser direct writing according to claim 1, characterized in that: The system for preparing a double-ring structure in one step based on laser direct writing can flexibly change the inner and outer diameters of the required double-ring structure by changing the power density and the direct writing time.

7. A method for preparing a double ring structure in one step based on laser direct writing, characterized in that: The steps include: Mounting a positive and negative adjustable photoresist sample on a three-dimensional high-precision nanopositioning translation stage; the positive and negative adjustable photoresist sample comprises a substrate and an S1813 positive photoresist coated on the substrate; the S1813 positive photoresist comprises a cresol novolac resin, a diazonaphthoquinone photosensitive compound, and a solvent; A continuous wave laser beam is emitted by a continuous laser; A beam expansion system is used to expand the continuous wave laser beam; An attenuator is used to control the energy of the continuous wave laser beam after beam expansion; A half-wave plate is used to control the polarization direction of the continuous wave laser beam; An optical shutter is used to control the light flux of a continuous wave laser beam; A beam splitter or polarization beam splitter prism is used to focus the incident continuous wave laser beam onto the surface of the positive and negative adjustable photoresist sample through an oil immersion objective lens. A portion of the laser beam incident on the surface of the positive and negative adjustable photoresist sample is reflected onto the beam splitter or polarization beam splitter prism and then irradiated onto the third lens. An oil-immersion objective is used to focus a laser beam onto a sample of positive and negative tunable photoresist, creating a double-ring structure in a single step. This structure is then developed using a developer. The principle is as follows: the laser wavelength and power, located at the edge of the photoresist's absorption region, are selected to create different intensities in different areas of the spot. These intensities result in non-reaction, chemical conversion, and ablation, respectively, in the corresponding areas, thereby producing the double-ring structure shown. Specifically, the applied laser beam can simultaneously produce ablated, negative, positive, and unexposed features in the polymer film. At this point, the solidified polymer is ablated in the center of the tightly focused beam. In the outer part of the tightly focused beam, the photoresist is converted from positive to negative, causing the polymer to solidify; in the extreme outer part of the focused beam, normal polymerization occurs and is removed in the subsequent development process; while in the non-focused part, the polymer film is not affected; A third lens is used to focus the laser beam onto the CCD camera; Use CCD camera to monitor the processing process in real time and observe the exposure of the light beam; Computer-controlled three-dimensional high-precision nanopositioning translation stage and CCD camera.

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