Infrared surface plasmon assisted thermal scanning probe nano etching system and method

Abstract

The invention provides an infrared surface plasmon assisted thermal scanning probe nanometer etching system. The infrared surface plasmon assisted thermal scanning probe nanometer etching system comprises a nanometer probe table, a surface plasmon probe, an infrared laser module and an etching sample. During working, the infrared laser module guides etching laser to the surface plasmon probe, and the vertex of the needle point is heated by utilizing local light field enhancement at the needle point; and when the nano probe station controls the surface plasmon probe to horizontally move above the etching sample according to a predetermined track, the heat at the needle tip volatilizes the thermosensitive resist on the surface of the etching sample, so that the nano pattern is etched in the thermosensitive resist. According to the invention, the low-cost infrared continuous wave laser can be utilized to realize deep sub-wavelength nano-etching with the line width of dozens of nanowires, a new technical path is provided for a nano-etching system with low cost and high precision, the threshold of a nano-processing technology is reduced, and popularization and application of the nano-etching technology are expected to be promoted.

Description

Technical Field

[0001] The present invention relates to the field of nano-processing technology, and in particular to an infrared surface plasmon-assisted thermal scanning probe nano-etching system and method. Background Art

[0002] Advances in nanofabrication technology have laid the foundation for modern nanoscience. Achieving nanoscale fabrication with finer patterns is crucial for a wide range of fields, including nanophotonics, metrology, and molecular biology. As the most mature commercial technology, photolithography provides the foundational platform for large-scale, high-throughput production of electronic and photonic devices. Limited by the optical diffraction limit, researchers are constantly exploring ways to shorten the wavelength of light sources to improve resolution. Decades of development have significantly pushed the boundaries of nanofabrication. However, high costs and complex processes limit their application in large-scale production and hinder their scalability to the nanofabrication of miniaturized and customized prototype devices. Maskless alternatives, such as electron beam lithography and focused ion beam lithography, have been widely used in basic nanotechnology research but still face challenges in balancing precision and cost. Laser direct writing, a low-cost, high-speed photolithography method, remains diffraction-limited in resolution. Therefore, the development of nanofabrication technologies that combine high precision, low cost, and flexibility remains an urgent need.

[0003] In recent years, surface plasmons have been applied to plasmonic near-field lithography, providing an innovative solution for reducing the feature size of nanofabrication using conventional ultraviolet light sources. By inducing localized surface plasmon resonances with spatial light or surface plasmons, plasmonic near-field lithography overcomes the inherent limitations of optical diffraction and confines the light field to deep subwavelength scales. Research has demonstrated that nanopatterning with a half-pitch of less than 50nm can be achieved using a 365nm wavelength light source, confirming the potential of plasmonic near-field lithography as a high-resolution, low-cost alternative to photolithography. Localized surface plasmon nanostructures, as the core components of plasmonic near-field lithography, generate subdiffraction-limited light spots through carefully designed nanoapertures or nanoparticles. For example, the resolution of plasmonic near-field lithography using ridge-shaped apertures depends primarily on the ridge gap size, and the resulting light spot is typically equal to or slightly larger than the minimum feature size of the localized surface plasmon nanostructure. In order to obtain a smaller spot, researchers have continuously reduced the critical dimensions of localized surface plasmon nanostructures to approach the processing limit of focused ion beam etching (<20nm), but this results in a time-consuming process and low yield. On the other hand, although traditional photoresists can be used for plasmon near-field lithography, studies have found that the thermal effect generated by localized surface plasmons combined with thermosensitive resists can further compress the feature size to 50% of the spot size. However, this method requires a large and expensive picosecond pulse laser system to suppress heat diffusion and control the exposure area. Therefore, the development of a high-precision nanoprocessing solution based on easy-to-process nanostructures and low-cost continuous wave lasers is of great significance for reducing equipment costs. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0005] To this end, the purpose of the present invention is to propose an infrared surface plasmon-assisted thermal scanning probe nano-etching system and method. By designing a number of precise annular grooves on the surface plasmon probe, the radially polarized excitation light is efficiently converted into infrared surface plasmons, and finally an ultra-strong localized surface plasmon spot is excited at the tip of the probe. Compared with the ultraviolet band, the surface plasmon excited by infrared light has lower transmission loss and can obtain a stronger near-field enhancement effect. At the same time, the longer working wavelength makes the nano-annular groove structure have a larger characteristic size (>100nm), which significantly reduces the processing difficulty. The deep subwavelength light field focusing generated by the infrared localized surface plasmon works synergistically with the photothermal effect to heat the tip of the probe to above the threshold temperature of the thermosensitive resist. It is particularly noteworthy that the annular groove structure can achieve excellent local heat focusing effects even under the irradiation of continuous wave lasers. Specifically, the annular groove localizes the light field at the tip apex of the surface plasmon probe, and the light field in the extremely small area near the tip apex is greatly enhanced. The tip is heated by the photothermal effect, and the localization of the light field can produce a local heat focusing effect, which not only reduces the required laser power, but also strictly limits the heat-affected zone to the nanometer scale. Based on these advantages, the invention successfully achieved sub-wavelength pattern processing with an etching line width of tens of nanometers using a near-infrared continuous wave laser with an output power of only tens of milliwatts. Compared with existing plasmon near-field lithography technology, the present invention is expected to further reduce the equipment cost and technical threshold of nano-processing.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides an infrared surface plasmon-assisted thermal scanning probe nanolithography system, comprising:

[0008] A surface plasmon probe, wherein the tip and reflective surfaces of the surface plasmon probe are both covered with a metal film, wherein the metal film on the tip is machined with a plurality of annular grooves serving as grating couplers, and the metal film on the reflective surface is machined with a light-transmitting hole;

[0009] An infrared laser module, comprising an infrared laser and an infrared laser optical path, wherein the infrared laser optical path guides the infrared etching laser emitted by the infrared laser to the surface plasmon probe, passes through the light-transmitting hole to the annular groove, excites localized surface plasmons at the tip apex of the surface plasmon probe, and utilizes the light field enhancement of the localized surface plasmons to heat the tip;

[0010] Etching a sample comprising a substrate and a thermally sensitive resist covering the substrate, wherein the thermally sensitive resist is a polymer material that thermally decomposes into volatile monomers when heated above a threshold temperature;

[0011] The nanoprobe station is used to control the surface plasmon probe to move along a predetermined track above the etched sample, and utilize the heat at the top of the needle tip to heat the thermosensitive resist and volatilize it, thereby etching a nano pattern on the thermosensitive resist.

[0012] In some embodiments, the material of the remaining portion of the surface plasmon probe except the metal film should allow near-infrared light to pass through.

[0013] In some embodiments, the tip of the surface plasmon probe is conical, and the cross-sectional size of the tip gradually decreases from the tip root to the tip apex.

[0014] In some embodiments, the radius of the annular groove should satisfy a phase matching condition, that is, the phase difference between infrared surface plasmons excited in any two annular grooves is an integer multiple of 2π.

[0015] In some embodiments, the infrared laser has a wavelength in the near-infrared band.

[0016] In some embodiments, the infrared laser optical path is formed between the emission end of the infrared laser and the surface plasmon probe, and is used to convert the infrared etching laser into a radially polarized light beam, and make the radially polarized light beam enter the surface plasmon probe in a direction parallel to the axial direction of the needle tip of the surface plasmon probe.

[0017] In some embodiments, the nanoprobe station includes a three-axis piezoelectric nanodisplacement stage and a built-in reflector and a laser beam focusing objective lens. The three-axis piezoelectric nanodisplacement stage is used to control the relative movement of the surface plasmon probe and the etched sample. The built-in reflector and the laser beam focusing objective lens are located between the infrared laser optical path and the surface plasmon probe.

[0018] In some embodiments, the nanoprobe station controls the surface plasmon probe to operate in contact mode or tapping mode during nanoetching. When operating in the tapping mode, the distance between the tip of the surface plasmon probe and the upper surface of the etched sample is less than 30 nm.

[0019] In some embodiments, the metal film covering the needle tip surface and the reflective surface is made of the same material and has the same thickness, with a thickness ranging from 50 nm to 100 nm;

[0020] The radius of curvature of the needle tip apex is less than 60 nm;

[0021] The aperture of the light-transmitting hole ranges from 6 μm to 12 μm;

[0022] The radius of the circular groove processed on the surface plasmon probe is in the range of 0.4 μm to 5.0 μm, the ring width is in the range of 100 nm to 300 nm, and the number is in the range of 2 to 8;

[0023] The thickness of the heat-sensitive resist ranges from 20 nm to 200 nm;

[0024] The thermal decomposition temperature of the thermosensitive resist should ensure that the surface plasmon probe is not damaged;

[0025] The emission power of the infrared laser is 20mW to 200mW.

[0026] A second aspect of the present invention provides an infrared surface plasmon-assisted thermal scanning probe nanolithography method, comprising:

[0027] Processing a surface plasmon probe, wherein the tip surface and the reflective surface of the surface plasmon probe are both covered with a layer of metal film, the metal film on the tip surface is processed with a plurality of annular grooves serving as grating couplers, and the metal film on the reflective surface is processed with a light-transmitting hole;

[0028] The surface plasmon probe is mounted above an etched sample, wherein the etched sample includes a substrate and a thermosensitive resist covering the substrate, wherein the thermosensitive resist is a polymer material that thermally decomposes into volatile monomers when heated above a threshold temperature;

[0029] guiding an infrared etching laser onto the surface plasmon probe, passing through the light-transmitting hole to reach the annular groove, exciting localized surface plasmons at the tip of the surface plasmon probe, and heating the tip by utilizing the light field enhancement of the localized surface plasmons;

[0030] The surface plasmon probe is controlled to move along a predetermined track above the etching sample, and the heat at the top of the needle tip is used to heat the thermosensitive resist and volatilize it, thereby etching a nano pattern on the thermosensitive resist.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The infrared surface plasmon-assisted thermal scanning probe nano-etching system and method provided by the present invention uses a large wavelength, low-cost, low-power infrared laser to achieve nano-processing of tens of nanometer feature sizes. It has the advantages of simple structure, high resolution and no need for a mask, and can break through the natural limitation of the optical diffraction limit on the lithography resolution in existing projection-type commercial lithography technology. In addition, compared with the existing thermal scanning direct writing nano-etching technology that integrates a heating module on the probe, the nano-etching system provided by the present invention is heated by an external infrared laser module. It can be modified by introducing an infrared laser module on the basis of any ordinary nano-probe station, and is not limited to nano-probe stations with electric heating modules, thereby improving the compatibility of the method. In summary, the nano-etching system and method provided by the present invention can achieve deep sub-wavelength resolution without the aid of expensive deep ultraviolet light sources and complex optical systems, reducing the equipment cost and technical threshold of high-precision nano-processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A schematic structural diagram of an infrared surface plasmon-assisted thermal scanning probe nanolithography system provided by an embodiment of the present invention;

[0035] Figure 2 A schematic structural diagram of an infrared laser module provided in an embodiment of the present invention;

[0036] Figure 3 A schematic structural diagram of a nanoprobe station provided in an embodiment of the present invention;

[0037] Figure 4 A schematic structural diagram of a surface plasmon probe provided in an embodiment of the present invention;

[0038] Figure 5 A schematic diagram of a circular groove on the tip of a surface plasmon probe provided by an embodiment of the present invention;

[0039] Figure 6 A schematic diagram of the nano-etching system according to an embodiment of the present invention performing nano-etching;

[0040] Description of reference numerals:

[0041] 1. Surface plasmon probe; 11. Tip; 12. Metal film on tip surface; 13. Metal film on reflective surface; 14. Annular groove; 15. Light-transmitting hole; 16. Tip apex;

[0042] 2. Infrared laser module; 21. Infrared laser; 22. Infrared laser optical path; 221. Linear polarizer; 222. Radially polarized light converter; 223. Reflector; 23. Infrared etching laser;

[0043] 3. Etching sample; 31. Substrate; 32. Thermosensitive resist; 33. Nanopattern;

[0044] 4. Nanoprobe station; 41. Built-in reflector; 42. Laser beam focusing objective lens; 43. Three-axis piezoelectric nanodisplacement stage. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0046] On the contrary, this application covers any alternatives, modifications, equivalents, and solutions made within the spirit and scope of this application as defined by the claims. Furthermore, to facilitate a better understanding of this application, certain specific details are described in detail below in the detailed description of this application. Those skilled in the art will be able to fully understand this application without these details.

[0047] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions for the implementation of this application, so they have no technical substantive significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in this application without affecting the efficacy and purpose that can be achieved by this application. At the same time, the terms such as "upper", "lower", "left", "right", "front", "back", "middle" and "one" quoted in this specification are only for the convenience of description and consistency with the orientation shown in the drawings, and are not used to limit the scope of the implementation of this application. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of this application without substantially changing the technical content.

[0048] like Figures 1 to 6 As shown, the infrared surface plasmon-assisted thermal scanning probe nano-etching system of the first embodiment of the present invention includes a surface plasmon probe 1, an infrared laser module 2, an etching sample 3 and a nano-probe station 4.

[0049] The upper and lower sides of the surface plasmon probe 1 are covered with a layer of metal film, namely the tip surface metal film 12 and the reflective surface metal film 13. The tip surface metal film 12 is processed with a number of annular grooves 14 as grating couplers, and the reflective surface metal film 13 is processed with a light-transmitting hole 15.

[0050] The infrared laser module 2 includes an infrared laser 21 and an infrared laser optical path 22. The infrared laser optical path 22 guides the infrared etching laser 23 emitted by the infrared laser 21 to the surface plasmon probe 1, passes through the light-transmitting hole 15 and reaches the annular groove 14, excites the localized surface plasmon at the needle tip apex 16 of the surface plasmon probe 1, and utilizes the optical field enhancement of the localized surface plasmon to heat the needle tip 11.

[0051] The etching sample 3 includes a substrate 31 and a thermal resist 32 covering the substrate 31. The thermal resist 32 is a polymer material that will thermally decompose into volatile monomers when heated above a threshold temperature.

[0052] The nanoprobe station 4 is used to control the surface plasmon probe 1 to move along a predetermined trajectory above the etched sample 3 , and utilizes the heat at the needle tip apex 16 to heat and volatilize the thermosensitive resist 32 , thereby etching a nano pattern 33 on the thermosensitive resist 32 .

[0053] Specifically, the surface plasmon probe 1 and the etching sample 3 are fixed on the nanoprobe station 4, which can control the relative movement of the two. The infrared laser module 2 is independently built outside the nanoprobe station 4 to provide a light source for the thermal scanning probe nanoetching system. Figure 1 The infrared etching laser 23 emitted by the infrared laser 21 passes through the infrared laser optical path 22, and the propagation direction and polarization state of the infrared etching laser 23 are adjusted, as shown in FIG. Figure 2 After the infrared laser light path 22 is adjusted, the infrared etching laser 23 enters the nanoprobe station 4, and is incident on the reflective metal film 13 of the surface plasmon probe 1 in a direction parallel to the axis of the needle tip 11. It enters the interior of the surface plasmon probe 1 through the light-transmitting hole 15 and finally irradiates the several annular grooves 14 processed on the metal film 12 on the needle tip surface, as shown in FIG. Figure 3 and Figure 4 The annular groove 14 acts as a grating coupler, converting the incident infrared etching laser 23 into infrared surface plasmons, as shown in FIG. Figure 5As shown. By carefully designing the radius of these annular grooves 14 to meet the phase matching condition, that is, the phase difference between the infrared surface plasmons excited in any two annular grooves is an integer multiple of 2π, the excited infrared surface plasmons will undergo constructive interference and be transmitted toward the tip apex 16. The tip apex 16 is a closed end, and the infrared surface plasmons are focused and compressed to the limit at the tip apex 16, forming a localized surface plasmon resonance, and the local light field intensity reaches a maximum. Due to the photothermal effect, the light field is converted into heat through the ohmic loss of the metal film, and the heat power per unit volume is proportional to the local light field intensity. It can be seen that the heat generation at the tip apex 16 is the most significant, the temperature reaches the highest, and the heat is localized in a very small space of tens of nanometers near the tip apex 16, thereby achieving the focusing of the thermal field. When the nanoprobe station 4 controls the surface plasmon probe 1 and the etching sample 3 to approach each other and move relative to each other, the high temperature at the tip apex 16 can instantly decompose and volatilize the thermal resist 32 on the surface of the etching sample 3, leaving an etched nano pattern 33 in the thermal resist 32, as shown in FIG. Figure 6 As shown. Due to the focusing effect of the surface plasmon probe 1 on the thermal field, the characteristic size of the heated area is only tens of nanometers. Therefore, a low-power, low-cost continuous wave laser can be used as the infrared laser of the embodiment of the present invention, effectively lowering the technical threshold of nano-processing. In addition, the surface plasmon probe 1 in the above embodiment can be prepared by the following method: first, a layer of metal film is plated on the tip surface and the reflective surface of a commercial scanning probe by physical or chemical vapor deposition, and then a circular groove is processed on the metal film on the tip surface and a light-transmitting hole is processed on the metal film on the reflective surface by focused ion beam etching.

[0054] In a specific embodiment, the infrared laser module 2 can be placed on the right side of the scanning probe station 4. After multiple reflections, the infrared etching laser 23 is irradiated from top to bottom in the scanning probe station 4 onto the surface plasmon probe 1. It should be noted that the specific position of the infrared laser module 2 can be designed by those skilled in the art according to actual conditions and is not specifically limited here.

[0055] Furthermore, the material of the rest of the surface plasmon probe 1 except the metal film 12 on the tip surface and the metal film 13 on the reflection surface is transparent to near-infrared light.

[0056] Specifically, the infrared etching laser 23 is incident on the light-transmitting hole 15 above the surface plasmon probe 1, and needs to pass through the interior of the surface plasmon probe 1 and finally reach the metal film 12 on the other side of the needle tip. Figure 4Only materials that are transparent to near-infrared light will not hinder the propagation of the infrared etching laser 23, and the material should have as low a refractive index and loss as possible, such as quartz and sapphire, to reduce the reflection and absorption of the infrared etching laser 23 and improve energy utilization efficiency.

[0057] Furthermore, the tip 11 of the surface plasmon probe 1 is conical, and the cross-sectional size of the tip 11 gradually decreases from the tip root to the tip apex 16. The curvature radius of the tip apex 16 is less than 60 nm. Under conditions permitted by the processing technology, the smaller the curvature radius, the better. The minimum curvature radius that can be achieved at this stage is 10 nm.

[0058] Specifically, the cross-sectional dimensions of the tip 11 gradually decrease from its base to its apex 16, ensuring that surface plasmons are continuously compressed during propagation, reaching their maximum compression at the apex 16, where the cross-sectional dimensions are smallest, and the localized light field reaches its peak. The radius of curvature of the apex 16, less than 60 nm, ensures that the characteristic dimensions of the region heated by the localized light field are on the order of tens of nanometers, effectively guaranteeing the precision of nanolithography.

[0059] Furthermore, the wavelength range of the infrared laser 21 is the near-infrared band.

[0060] Specifically, the near-infrared band is selected as the working band of the thermal scanning probe nanoetching system of the present invention for the following two considerations. On the one hand, compared with the ultraviolet band, the loss of metal materials in the near-infrared band is smaller, and the surface plasmons excited by near-infrared light have lower transmission loss, which can obtain a stronger near-field enhancement effect. At the same time, the longer working wavelength makes the annular groove 14 have a larger characteristic size (ring width>100nm), which reduces the processing difficulty of the needle tip 11. On the other hand, due to the lateral size of the surface plasmon probe 1, the maximum radius of the annular groove 14 is less than 5.0μm. The larger the working wavelength, the smaller the number of annular grooves 14 that can be designed to meet the phase matching condition. This will weaken the constructive interference of the infrared surface plasmons and reduce the local light field intensity at the needle tip 16, which is not conducive to the realization of the thermal scanning probe nanoetching function. Therefore, the near-infrared band is a suitable working band for the thermal scanning probe nanoetching system of the present invention. For example, commonly used laser wavelengths of 1064nm and 1550nm can be selected.

[0061] Furthermore, the infrared laser optical path 22 includes a linear polarizer 221 , a radial polarization converter 222 , and two reflectors 223 , where the two reflectors are a first reflector and a second reflector.

[0062] Specifically, the infrared etching laser 23 is first converted into a linearly polarized beam in the horizontal direction by the linear polarizer 221, and then converted into a radially polarized beam by the radial polarization converter 222. The polarization direction of the radially polarized light changes with the change of the azimuth angle, and is always radially polarized in the cross section of the beam. When the laser beam in this polarization state is irradiated onto the annular groove 14 on the surface plasmon probe 1, it can efficiently excite surface plasmons. The reflector 223 is used to change the propagation direction and position of the infrared etching laser 23 passing through the radial polarization converter 222, such as Figure 2 shown.

[0063] It should be noted that those skilled in the art can set the specific number, position and placement order of each optical element in the infrared laser light path 22 according to actual conditions. In order to optimize the intensity of the localized surface plasmon light field excited at the needle tip 16, other optical elements such as apertures and wave plates can also be added, which are not specifically limited here.

[0064] Furthermore, the nano-probe station 4 includes a built-in reflector 41 and a laser beam focusing lens 42 .

[0065] Specifically, the infrared etching laser 23 emitted from the infrared laser module 2 enters the nanoprobe station 4 from the side, is reflected by the built-in reflector 41, and propagates downward, and its propagation direction is parallel to the axial direction of the needle tip 11. The laser beam focusing objective 42 is used to further focus the infrared etching laser 23 to increase the energy density of the beam. After focusing, the focus of the laser beam falls on the light-transmitting hole 15 of the surface plasmon probe 1, as shown in FIG. Figure 3 shown.

[0066] Furthermore, the nanoprobe station 4 further includes a three-axis piezoelectric nanodisplacement stage 43 , which can control the relative movement between the surface plasmon probe 1 and the etched sample 3 .

[0067] Specifically, the three-axis piezoelectric nano-displacement stage 43 has the advantages of simple structure and high scanning accuracy. It can achieve a picometer-level movement resolution in the horizontal and vertical directions, and can control the relative positions of the surface plasmon probe 1 and the etched sample 3 in the vertical and horizontal directions. Figure 3 As shown. In the vertical direction, the needle tip 11 maintains contact with the etched sample 3 or hovers precisely and stably at a height of several nanometers to tens of nanometers above the etched sample 3. In this way, the local thermal field at the needle tip apex 16 causes the heat-sensitive resist 32 on the upper surface of the etched sample 3 to decompose and volatilize. In the lateral direction, the needle tip 11 moves relative to the etched sample 3 point by point, and the needle tip 11 scans the etched points to form a nano pattern 33, thereby achieving high-precision and high-resolution thermal scanning probe nano-etching, as shown. Figure 6 shown.

[0068] Furthermore, the nanoprobe station 4 can control the surface plasmon probe 1 to operate in contact mode or tapping mode during nanoetching. When operating in the tapping mode, the distance between the tip 16 of the surface plasmon probe 1 and the upper surface of the etched sample 3 is less than 30 nm.

[0069] Specifically, in contact mode, the needle tip 11 maintains contact with the etched sample 3, and in tapping mode, the distance between the needle tip 11 and the upper surface of the etched sample 3 is within 30 nm. The purpose is to use the highly localized thermal field at the needle tip apex 16 to heat the thermosensitive resist 12, so that the size of the heated area is equivalent to the diameter of the needle tip apex 16, so that the minimum feature size of the etched nano pattern 33 is on the order of tens of nanometers.

[0070] Furthermore, the tip surface metal film 12 and the reflective surface metal film 13 are made of the same material and have the same thickness, and the thickness ranges from 50 nm to 100 nm.

[0071] Specifically, both sides of the surface plasmon probe 1 are covered with a metal film of the same thickness and material. This ensures that the probe expands uniformly on both sides after laser heating, preventing warping caused by uneven thermal expansion, which could affect nano-etching accuracy or even damage the probe. For example, the metal film can be made of gold, platinum, or chromium. A metal film thickness of 50nm to 100nm prevents direct transmission of the infrared etching laser 23 while also facilitating the infrared etching laser 23 reaching the annular groove 14 to excite surface plasmons.

[0072] Furthermore, the aperture of the light-transmitting hole 15 ranges from 6 μm to 12 μm.

[0073] Specifically, the light-transmitting hole should be large enough, close to or equal to the beam diameter of the infrared etching laser 23, to reduce energy loss caused by reflection, but it is necessary to try to avoid the aperture being too large to damage the metal film on the upper surface of the surface plasmon probe 1, so its aperture range is limited.

[0074] Furthermore, the radius of the circular grooves 14 processed on the surface plasmon probe 1 ranges from 0.4 μm to 5.0 μm, the width of the ring ranges from 100 nm to 300 nm, and the number ranges from 2 to 8.

[0075] Specifically, the radius design of the annular groove 14 needs to meet the phase matching condition, so that the phase difference of the surface plasmon excited by each annular groove is an integer multiple of 2π, so that all excited surface plasmons can constructively interfere at the needle tip apex 16. The ring width range of the annular groove 14 is approximately sub-wavelength, which prevents the infrared etching laser 23 from directly passing through the annular groove 14, while also reducing interference with the surface plasmon transmission. The number range of the annular grooves 14 is limited by the lateral size of the surface plasmon probe 1. Under the condition that the largest annular groove does not exceed the boundary of the surface plasmon probe 1, designing more annular grooves can increase the local light field intensity at the needle tip apex 16, which is beneficial to the focusing of the light field and thermal field. The radius, ring width and number of the annular groove 14 can be designed through electromagnetic simulation optimization. For example, in one embodiment of the present invention, the number of the annular grooves is 4, the ring widths are all 200 nm, and the radii of the four annular grooves are 1.4 μm, 2.6 μm, 3.3 μm and 3.8 μm respectively.

[0076] Furthermore, the thickness of the thermal resist 32 is in the range of 20 nm to 200 nm.

[0077] Specifically, the heat field generated by the infrared etching laser 23 is highly localized near the tip apex 16 , and the nano-etching depth of the surface plasmon probe 1 does not exceed 200 nm, thus limiting the thickness of the thermal resist 32 to 20 nm to 200 nm.

[0078] Furthermore, the thermal decomposition temperature of the thermosensitive resist 32 should be such as to ensure that the surface plasmon probe 1 is not damaged.

[0079] Specifically, to avoid damage to the surface plasmon probe 1 due to excessive heating, such as deformation, melting, etc., the thermal decomposition temperature of the thermosensitive resist 32 should be lower than the melting point of the needle tip metal film 12 and the reflective surface metal film 13, and a certain redundancy should be retained. Therefore, the thermal decomposition temperature of the thermosensitive resist 32 can be limited to below 500 degrees Celsius. For example, the thermosensitive resist 32 can be selected as polyphthalaldehyde (PPA).

[0080] Furthermore, the emission power of the infrared laser 21 is 20 mW to 200 mW.

[0081] Specifically, excessive emission power of the infrared laser 21 may cause the surface plasmon probe 1 to be heated to excessive temperatures and damaged, so its emission power is limited to below 200 mW. In fact, due to the simultaneous focusing of the optical and thermal fields by the surface plasmon probe 1, the present invention only requires a low-power laser of tens of mW (e.g., 20 mW) to achieve nano-etching.

[0082] The second aspect of the present invention provides an infrared surface plasmon-assisted thermal scanning probe nanolithography method, comprising the following steps:

[0083] Processing a surface plasmon probe, wherein the tip surface and the reflective surface of the surface plasmon probe are both covered with a layer of metal film, a plurality of annular grooves serving as grating couplers are processed in the metal film on the tip surface, and a light-transmitting hole is processed in the metal film on the reflective surface;

[0084] A surface plasmon probe is mounted above an etched sample, the etched sample comprising a substrate and a thermosensitive resist covering the substrate, the thermosensitive resist being a polymer material that thermally decomposes into volatile monomers when heated above a threshold temperature;

[0085] An infrared etching laser is directed onto the surface plasmon probe, passing through the light-transmitting hole of the surface plasmon probe to reach the annular groove, thereby exciting localized surface plasmons at the tip of the surface plasmon probe, and utilizing the optical field enhancement of the localized surface plasmons to heat the tip;

[0086] The surface plasmon probe is controlled to move along a predetermined trajectory above the etched sample, and the heat at the top of the needle tip is used to heat the thermosensitive resist and volatilize it, thereby etching a nano-pattern on the thermosensitive resist.

[0087] It should be noted that the aforementioned explanation of the embodiment of the infrared surface plasmon-assisted thermal scanning probe nanoetching system is also applicable to the infrared surface plasmon-assisted thermal scanning probe nanoetching method of this embodiment, and will not be repeated here.

[0088] Throughout this specification, reference to terms such as "one specific embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0089] Although the embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. An infrared surface plasmon-assisted thermal scanning probe nanolithography system, characterized in that: include: A surface plasmon probe, wherein the tip and reflective surfaces of the surface plasmon probe are both covered with a metal film, wherein the metal film on the tip is machined with a plurality of annular grooves serving as grating couplers, and the metal film on the reflective surface is machined with a light-transmitting hole; An infrared laser module, comprising an infrared laser and an infrared laser optical path, wherein the infrared laser optical path guides the infrared etching laser emitted by the infrared laser to the surface plasmon probe, passes through the light-transmitting hole to the annular groove, excites localized surface plasmons at the tip apex of the surface plasmon probe, and utilizes the light field enhancement of the localized surface plasmons to heat the tip; Etching a sample comprising a substrate and a thermally sensitive resist covering the substrate, wherein the thermally sensitive resist is a polymer material that thermally decomposes into volatile monomers when heated above a threshold temperature; The nanoprobe station is used to control the surface plasmon probe to move along a predetermined track above the etched sample, and utilize the heat at the top of the needle tip to heat the thermosensitive resist and volatilize it, thereby etching a nano pattern on the thermosensitive resist.

2. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The material of the remaining portion of the surface plasmon probe except the metal film should allow near-infrared light to pass through.

3. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The tip of the surface plasmon probe is conical, and the cross-sectional size of the tip gradually decreases from the tip root to the tip apex.

4. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The radius of the annular groove should satisfy the phase matching condition, that is, the phase difference between the infrared surface plasmons excited in any two annular grooves is an integer multiple of 2π.

5. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The wavelength range of the infrared laser is near infrared band.

6. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The infrared laser optical path is formed between the emission end of the infrared laser and the surface plasmon probe, and is used to convert the infrared etching laser into a radially polarized light beam, and make the radially polarized light beam enter the surface plasmon probe in a direction parallel to the axial direction of the needle tip of the surface plasmon probe.

7. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The nanoprobe station includes a three-axis piezoelectric nanodisplacement stage, a built-in reflector, and a laser beam focusing objective lens. The three-axis piezoelectric nanodisplacement stage is used to control the relative movement of the surface plasmon probe and the etched sample. The built-in reflector and the laser beam focusing objective lens are located between the infrared laser light path and the surface plasmon probe.

8. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The nanoprobe station controls the surface plasmon probe to operate in contact mode or tapping mode during nanoetching. When operating in the tapping mode, the distance between the tip of the surface plasmon probe and the upper surface of the etched sample is less than 30 nm.

9. The infrared surface plasmon-assisted thermal scanning probe nanolithography system according to claim 1, characterized in that: The metal film covering the needle tip surface and the reflective surface has the same material and thickness, and the thickness ranges from 50nm to 100nm; The radius of curvature of the needle tip apex is less than 60 nm; The aperture of the light-transmitting hole ranges from 6 μm to 12 μm; The radius of the circular groove processed on the surface plasmon probe is in the range of 0.4 μm to 5.0 μm, the ring width is in the range of 100 nm to 300 nm, and the number is in the range of 2 to 8; The thickness of the heat-sensitive resist ranges from 20 nm to 200 nm; The thermal decomposition temperature of the thermosensitive resist should ensure that the surface plasmon probe is not damaged; The emission power of the infrared laser is 20mW to 200mW.

10. An infrared surface plasmon-assisted thermal scanning probe nanolithography method, characterized in that: include: Processing a surface plasmon probe, wherein the tip surface and the reflective surface of the surface plasmon probe are both covered with a layer of metal film, the metal film on the tip surface is processed with a plurality of annular grooves serving as grating couplers, and the metal film on the reflective surface is processed with a light-transmitting hole; The surface plasmon probe is mounted above an etched sample, wherein the etched sample includes a substrate and a thermosensitive resist covering the substrate, wherein the thermosensitive resist is a polymer material that thermally decomposes into volatile monomers when heated above a threshold temperature; guiding an infrared etching laser onto the surface plasmon probe, passing through the light-transmitting hole to reach the annular groove, exciting localized surface plasmons at the tip of the surface plasmon probe, and heating the tip by utilizing the light field enhancement of the localized surface plasmons; The surface plasmon probe is controlled to move along a predetermined track above the etching sample, and the heat at the top of the needle tip is used to heat the thermosensitive resist and volatilize it, thereby etching a nano pattern on the thermosensitive resist.

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