A photolithography medium and a preparation method of micro-nano structures

Abstract

The embodiment of the present application provides a photoetching medium for preparing a micro-nano structure, the micro-nano structure comprising a substrate and a pattern layer on the substrate, the pattern layer being formed by the photoetching medium, and the photoetching medium being made of a heat-sensitive photoresist. The photoetching medium provided by the embodiment of the present application can realize high-resolution patterning of the micro-nano structure at a nanometer level through application of the heat-sensitive photoresist. The embodiment of the present application further provides a preparation method of the micro-nano structure.

Description

Technical Field

[0001] This application belongs to the field of micro-nano manufacturing technology, and in particular relates to a method for preparing photolithography media and micro-nano structures. Background Technology

[0002] Thermal scanning probe lithography (t-SPL) is an advanced nanofabrication method that achieves high-resolution patterning through localized thermal energy. The thermal probe consists of a pointed heating element that induces chemical or physical changes in the material surface through localized heating when the probe comes into contact with it. The core of this technology lies in the precise control of heat transfer to ensure the micro-size and high uniformity of the processed area.

[0003] Thermosensitive photoresist is a key material in t-SPL, and its performance directly determines the processing resolution and efficiency. Thermosensitive photoresist needs to possess thermal responsiveness and high-resolution characteristics, enabling it to react rapidly under certain thermal stimuli to form patterns, while also adapting to nanoscale processing requirements to create smooth boundaries and clear patterns. Existing photoresists are insufficient to meet these requirements. Summary of the Invention

[0004] To address the problems existing in the aforementioned related technologies, this invention provides a method for fabricating photolithography media and micro / nano structures. By applying thermal photoresist, high-resolution patterning of micro / nano structures can be achieved at the nanoscale.

[0005] In a first aspect, embodiments of this application provide a photolithography medium for fabricating micro / nano structures, the micro / nano structures including a substrate and a patterned layer on the substrate, the patterned layer being formed by the photolithography medium, the photolithography medium being made of thermal photoresist.

[0006] Furthermore, the thermal photoresist is PPC, and the photolithography medium is formed from a PPC solution with a concentration of 6.5%.

[0007] Furthermore, the PPC solution is formed by dissolving PPC solid particles in anisole solvent.

[0008] Furthermore, the thickness of the PPC film is between 250 nm and 300 nm.

[0009] Furthermore, the thermal decomposition temperature of the PPC film is greater than 300°C.

[0010] Secondly, embodiments of this application provide a method for preparing micro / nano structures, comprising the following steps:

[0011] Spin-coating a thermal photoresist onto a substrate; and

[0012] A cutout pattern is etched on the thermal photoresist to form a pattern layer on the substrate.

[0013] Further, the thermal photoresist is PPC, and the spin-coating of the thermal photoresist on the substrate includes:

[0014] The prepared PPC solution was dropped onto the substrate surface; and

[0015] The PPC film is formed on the substrate by a spin coating process.

[0016] Furthermore, the concentration of the PPC solution is 6.5%.

[0017] Further, the etching of a cutout pattern on the photoresist film to form a pattern layer on the substrate includes:

[0018] An array pattern is etched onto the photoresist film using a thermal probe; and

[0019] The hollow pattern is etched onto the array pattern using a plasma processing method to form the pattern layer on the substrate.

[0020] Further, the method of etching the perforated pattern on the array pattern using plasma processing to form a pattern layer on the substrate includes:

[0021] The array pattern is etched multiple times in a short period of time using a plasma treatment method to form the hollow pattern, and the pattern layer is formed on the substrate.

[0022] This application provides a photolithography medium for forming a patterned layer on a substrate of micro-nano structures. The photolithography medium is made of thermal photoresist. By applying thermal photoresist, high-resolution patterning of micro-nano structures can be achieved at the nanoscale, making it suitable for the fabrication of ultra-high density integrated circuits and nanoscale functional devices. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the line pattern and height curve etched by a thermal probe on the photolithographic medium provided in the embodiments of this application;

[0025] Figure 2A schematic diagram illustrating the relative relationship between the pattern etched by the thermal probe on the photolithographic medium provided in this embodiment and the set temperature;

[0026] Figure 3 A schematic diagram of the AFM scanning pattern, 3D pattern and height scanning curve of the photolithography medium provided in the embodiments of this application, which is etched by a thermal probe using a sinusoidal curve.

[0027] Figure 4 This is a schematic flowchart illustrating the fabrication method of the micro / nano structures provided in the embodiments of this application.

[0028] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. Those skilled in the art will be able to understand the specific meaning of the above terms in this application according to the specific circumstances.

[0032] This application provides a photolithography medium for fabricating micro / nano structures. The micro / nano structures include a substrate and a patterned layer on the substrate. The patterned layer is formed by the photolithography medium, which is made of thermal photoresist.

[0033] Specifically, as a thermally sensitive material, thermal photoresist can achieve precise patterning at the nanoscale through the thermal effect of scanning thermal probe lithography, breaking through the diffraction limit of traditional lithography. The minimum feature size can be as low as below 50nm, making it suitable for the manufacture of ultra-high density integrated circuits and nanoscale functional devices.

[0034] Meanwhile, by employing scanning thermal probe lithography, wet processing steps such as development and etching are eliminated. Patterning is directly completed through the thermal probe, followed by electrode formation through plasma treatment and evaporation, achieving all-dry manufacturing and significantly reducing processing steps and contamination risks. Furthermore, the thermal photoresist can be applied to a variety of substrates and exhibits excellent stability and compatibility in subsequent processing, making it suitable for the fabrication of more types of nanodevices.

[0035] In addition, thermal probe lithography is insensitive to external humidity and temperature, and directly processes patterns using thermal effects, avoiding the uncertainties caused by environmental fluctuations in wet processes, and improving the consistency and reproducibility of patterns.

[0036] Therefore, embodiments of this application provide a photolithography medium for forming a patterned layer on a substrate of micro-nano structures. The photolithography medium is made of thermal photoresist. By applying thermal photoresist, high-resolution patterning of micro-nano structures can be achieved at the nanoscale, making it suitable for the fabrication of ultra-high density integrated circuits and nanoscale functional devices.

[0037] Furthermore, the thermal photoresist is PPC (Polypropylene carbonate), and the photolithography medium is formed from a PPC solution with a concentration of 6.5%.

[0038] Specifically, PPC materials exhibit thermal decomposition at high temperatures. In thermogravimetric analysis (TGA), when the temperature exceeds 300°C, the mass loss approaches 100%. For example, a prepared PPC solution is dropped onto a substrate, such as a SiO2 / Si silicon wafer (SiO2 thickness 285 nm), using a pipette to cover the entire sample surface. Then, a spin coater is used for spin coating (low speed 1000 rpm for 10 s + high speed 9900 rpm for 60 s). After spin coating, a thin PPC film is obtained. Because of the strong adhesion between PPC molecules and the high spin coating speed, the spin coating thickness fluctuates within a certain range during high-speed spin coating. In scanning thermal probe microanalysis (STM) technology, the heated probe tip reaches the pyrolysis temperature of PPC. A pyrolysis reaction occurs at the PPC layer contacted by the heated probe. When the probe tip temperature exceeds the pyrolysis temperature, the PPC around the tip sublimates directly, forming a pattern.

[0039] Reference Figure 1 , Figure 1 This is a schematic diagram of the line patterns and height curves etched by a thermal probe onto the photolithographic medium provided in this application embodiment. PPC, as a thermal photoresist, can achieve relatively low etch precision. Figure 1 As can be seen, PPC, as a thermal photoresist, can achieve good writing performance in the submicron precision range, and at its minimum writing precision, it can reach a width of about 20nm. Figure 1The image also shows the height curve of the engraved pattern, from... Figure 1 As can be seen, there is accumulation at the edges of the etched lines. When the nanoscale is reached, the contact time between the probe and the sample surface is only tens of microseconds, which means that the heat on the probe cannot be fully applied to the sample layer, resulting in the accumulation of some thermal adhesive layer.

[0040] Reference Figure 2 , Figure 2 This diagram illustrates the relative relationship between the pattern etched by the photolithographic medium provided in this embodiment and the set temperature. The scanning thermal probe operates through the heat of the probe tip and the adhesive layer; therefore, the etched pattern on the sample surface varies with the set temperature. Figure 2 As shown, Figure 2 The temperature displayed is the temperature set in the instrument software, while the actual temperature of the needle tip is approximately one-third of the temperature set in the software. The complete thermal decomposition temperature of PPC material is slightly greater than 300℃, therefore... Figure 2 In summary, when the set temperature reaches approximately 900℃, it can achieve a relatively good writing effect on PPC.

[0041] Reference Figure 3 , Figure 3 This application provides an embodiment of a photolithography medium for which a sinusoidal curve is written using a thermal probe, illustrating the AFM scanning pattern, 3D pattern, and height scanning curve. Using a scanning thermal probe technique to write PPC has an advantage not found in traditional photolithography: it allows for custom writing in a third dimension, namely the vertical depth direction. Figure 3 As shown, a grayscale pattern can be used to depict a PPC with a sinusoidal curve in the vertical direction. Figure 3 The left image (a) shows the AFM scanning pattern on the sample surface after writing, the middle image (b) shows the corresponding 3D pattern, and the right image (c) shows the height scanning curve at the dashed line position in the left image (a). By writing at different depths in the vertical direction, it can be used for subsequent grayscale amplification in micro-nano fabrication.

[0042] In summary, this application's embodiments, by employing PPC as a thermal photoresist and combining it with scanning thermal probe technology, achieve ultra-high resolution patterning down to sub-100nm and even below 50nm, breaking through the limitations of traditional photolithography. This technical solution also enables precise patterning on various substrates, and PPC material's high thermal stability allows it to withstand high-temperature processing, solving the problem of limited material selection in traditional photoresists. Furthermore, the precise thermal effect processing of the scanning thermal probe avoids the sensitivity of traditional photolithography to humidity and temperature, improving pattern accuracy and stability. Overall, this application's embodiments provide a more efficient, flexible, and environmentally friendly solution for micro-nano manufacturing.

[0043] Furthermore, it should be noted that PMMA (polymethyl methacrylate) is used as a thermal photoresist to replace PPC. PMMA is a common photoresist material widely used in electron beam lithography and other micro / nano fabrication technologies. By adjusting the photosensitivity and thermal response characteristics of PMMA, it can be used as an alternative photoresist material for thermal probe lithography. PMMA has low thermoplasticity and can soften rapidly under heating conditions, thus meeting the requirements of scanning thermal probe technology.

[0044] Furthermore, the PPC solution is formed by dissolving PPC solid particles in anisole solvent.

[0045] Specifically, 1.5g of polypropylene carbonate (PPC) solid particles were dissolved in 21.5g of anisole solvent, resulting in a solution concentration of 1.5 / 23 = 6.522%. The solution was then stirred at 50°C for 24 hours using a magnetic stirrer to obtain the target PPC solution.

[0046] Furthermore, the thickness of the PPC film is between 250 nm and 300 nm.

[0047] For example, a prepared PPC solution is dropped onto a substrate, such as a SiO2 / Si silicon wafer (SiO2 thickness 285nm), using a pipette to cover the entire sample surface. Then, a spin coater is used for spin coating (low speed 1000rpm 10s + high speed 9900rpm 60s). After spin coating, a thin PPC film with a thickness of approximately 250nm-300nm is obtained. Because PPC molecules have strong adhesion and the spin coating process is fast, the spin coating thickness fluctuates within a certain range during high-speed spin coating.

[0048] Furthermore, the thermal decomposition temperature of the PPC film is greater than 300°C.

[0049] As mentioned above, PPC material exhibits thermal decomposition at high temperatures. In thermogravimetric analysis, its mass loss approaches 100% when the temperature exceeds 300°C. Therefore, in scanning thermal probe microanalysis (t-SPL), the heated probe tip can reach the pyrolysis temperature of PPC. A pyrolysis reaction will occur at the PPC layer in contact with the heated probe. When the probe tip temperature is higher than the pyrolysis temperature, the PPC around the probe tip will sublimate directly, forming a pattern.

[0050] Secondly, referring to Figure 4 This application provides a method for preparing micro / nano structures, comprising the following steps:

[0051] S101: Spin-coating thermal photoresist onto the substrate; and

[0052] S102: Etch a hollow pattern on the thermal photoresist to form a pattern layer on the substrate.

[0053] In the method for fabricating micro / nano structures provided in this application embodiment, a photoresist film is first spin-coated on a substrate, and then a hollow pattern is etched on the photoresist film to form a pattern layer on the substrate. The photoresist medium is made of thermal photoresist. Through the application of thermal photoresist, high-resolution patterning of micro / nano structures can be achieved at the nanoscale, which is suitable for the fabrication of ultra-high density integrated circuits and nanoscale functional devices.

[0054] It should be noted that after etching the cutout pattern on the thermal photoresist to form a pattern layer on the substrate, the following steps are also included:

[0055] S103: Deposit a metallic dielectric onto the exposed portions of the patterned layer and the substrate; and

[0056] S104: Apply adhesive to the metal medium on the patterned layer, and remove the patterned layer and the metal medium above the patterned layer by mechanically peeling off the adhesive to prepare a micro / nano structure including the substrate and the metal layer.

[0057] In the micro / nano structure fabrication method provided in this application embodiment, a photoresist film is first spin-coated onto a substrate. Then, a hollow pattern is etched onto the photoresist film to form a pattern layer on the substrate. A metal dielectric is then deposited on the exposed portions of the pattern layer and the substrate. Finally, an adhesive is applied to the metal dielectric on the pattern layer, and the pattern layer and the metal dielectric above the pattern layer are removed by mechanically peeling off the adhesive to fabricate a micro / nano structure including the substrate and the metal layer. Therefore, the micro / nano structure fabrication method provided in this application embodiment, through high-precision pattern etching, dry stripping processes, and efficient processing capabilities, can improve the resolution and processing efficiency of micro / nano structures, and can reduce costs and avoid environmental pollution problems.

[0058] Further, the thermal photoresist is PPC, and the spin-coating of the thermal photoresist on the substrate includes:

[0059] The prepared PPC solution was dropped onto the substrate surface; and

[0060] The PPC film is formed on the substrate by a spin coating process.

[0061] Specifically, PPC (Polypropylene Carbonate) materials exhibit thermal decomposition at high temperatures. In thermogravimetric analysis, its mass loss approaches 100% when the temperature exceeds 300°C. For example, a prepared PPC solution is dropped onto a substrate, such as a SiO2 / Si silicon wafer (SiO2 thickness 285 nm), using a pipette to cover the entire sample surface. Then, a spin coater is used for spin coating (low speed 1000 rpm for 10 s + high speed 9900 rpm for 60 s). After spin coating, a thin PPC film with a thickness of approximately 250 nm-300 nm is obtained. Because of the strong adhesion between PPC molecules and the high spin speed during the high-speed spin coating process, the spin coating thickness fluctuates within a certain range.

[0062] Furthermore, the concentration of the PPC solution is 6.5%. That is, 1.5g of polypropylene carbonate (PPC) solid particles need to be dissolved in 21.5g of anisole solvent, resulting in a solution concentration of 1.5 / 23 = 6.522%. The solution is then stirred at 50°C for 24 hours using a magnetic stirrer to obtain the target PPC solution for subsequent spin coating operations.

[0063] Further, the etching of a cutout pattern on the photoresist film to form a pattern layer on the substrate includes:

[0064] An array pattern is etched onto the photoresist film using a thermal probe; and

[0065] The hollow pattern is etched onto the array pattern using a plasma processing method to form the pattern layer on the substrate.

[0066] Specifically, in scanning thermal probe microscopy (t-SPL), the heated tip reaches the pyrolysis temperature of PPC. A pyrolysis reaction occurs at the PPC layer where the probe contacts the tip. When the tip temperature exceeds the pyrolysis temperature, the PPC around the tip sublimates directly, forming a pattern. The PPC around the probe, where the temperature is insufficient for sublimation, melts. During the probe's movement and writing process, the force applied to the probe pushes the melt, causing some PPC to accumulate at the pattern edges. T-SPL supports pattern import, enabling the writing of arbitrary patterns.

[0067] The thermal probe can etch a pattern on the surface of the PPC sample to a depth of 180 nm, which can be set. After the pattern array is etched, the PPC sample is treated with O2 / Ar plasma. During the plasma treatment, the PPC on the surface is reacted away, which reduces the thickness of the PPC layer.

[0068] The micro / nano structure fabrication method provided in this application, by precisely controlling the heating temperature and scanning path of the thermal probe, can achieve micron-level pattern etching and high-precision etching of metal patterns at the nanometer level (below 100 nm). This overcomes the resolution limitations of traditional photolithography, meets the high-precision pattern requirements of microelectronics and nanodevice manufacturing, and can efficiently process different materials (such as polymers, metals, and semiconductors), exhibiting strong material adaptability. Through localized heating, it avoids thermal damage associated with traditional high-temperature etching, making it particularly suitable for processing flexible substrates and temperature-sensitive materials. Furthermore, compared to traditional multiple exposure and development processes, t-SPL technology achieves pattern etching through a single scan, improving production efficiency. Its flexible processing method allows for rapid adjustment and optimization of processing conditions to adapt to different sizes and complex patterns.

[0069] It should be noted that the embodiments of this application can use laser beams or electron beams to replace the heating method of scanning thermal probes. For example, a focused laser beam can be used to locally heat the sample surface. Utilizing the high-precision focusing characteristics of lasers, pattern etching can also be achieved at the nanoscale. Other nanofabrication techniques, such as nanoimprint lithography or focused ion beam etching, can also be considered as alternative methods. Nanoimprint lithography transfers patterns by applying imprinting force to the material surface, while focused ion beam etching directly etches the material by accelerating the ion beam.

[0070] Furthermore, embodiments of this application can also utilize other non-thermal methods, such as photolithography, electron beam lithography, and ultrasonic etching, to perform pattern transfer at the micro-nano scale. Although the above methods differ in principle, they can all achieve high-precision pattern transfer.

[0071] Further, the method of etching the perforated pattern on the array pattern using plasma processing to form a pattern layer on the substrate includes:

[0072] The array pattern is etched multiple times in a short period of time using a plasma treatment method to form the hollow pattern, and the pattern layer is formed on the substrate.

[0073] Specifically, the PPC samples were treated with 5W O2 plasma or 5WAr plasma. The gas flow rate was 250 ml / min, and the treatment time was 3 min + 3 min + 3 min, with multiple short treatments to prevent the temperature from becoming too high during the plasma process, which would cause the etching rate to be too fast.

[0074] Furthermore, in some embodiments of this application, the metal layer includes a first metal layer and a second metal layer, with the second metal layer located above the first metal layer.

[0075] Specifically, once it is ensured that the PPC patterned positions have been etched onto the SiO2 / Si substrate during plasma processing, the next step of metal evaporation is performed. In this embodiment, a metal dielectric is deposited on the sample surface using EBE (Electron Beam Evaporation), ultimately forming a micro / nano structure including the substrate and a metal layer. The metal layer includes a first metal layer and a second metal layer, with the second metal layer positioned above the first metal layer.

[0076] Furthermore, in some embodiments of this application, the material of the first metal layer is Cr (chromium) or Au (gold).

[0077] Specifically, for example, Cr and Au can be deposited on the sample surface as metal patterns, Au can serve as device electrodes, and Cr can significantly enhance the adhesion between Au and the substrate.

[0078] Furthermore, in some embodiments of this application, the thickness of the first metal layer is 3 to 7 nm, and the thickness of the second metal layer is 15 to 20 nm.

[0079] For example, 5nm Cr and 20nm Au can be deposited on the sample surface as a metal pattern. Of course, the specific thickness of the metal layer depends on the actual situation and is not limited here.

[0080] After the metal dielectric deposition is complete, the sample can be placed on a glass slide, and then one or two layers of 3M tape can be applied to the sample surface. The surface should be gently pressed with tweezers to ensure full contact between the tape and the sample surface. Then, starting from one corner of the sample, the tape should be slowly peeled off. The metal layer at the patterned location will remain on the substrate, while the PPC and metal layers at other locations will be lifted by the tape, leaving only the metal pattern.

[0081] It should be noted that the embodiments of this application realize the preparation of metal patterns on SiO2 / Si substrates using a completely dry method. By combining thermal probe writing and plasma treatment, the preparation of micro-nano metal structures is realized through a completely dry method. Any micro-nano pattern can be realized through thermal probe technology and subsequent dry stripping technology, which is not limited here.

[0082] Furthermore, this application also provides a micro / nano structure, which is fabricated by the method described in any of the above embodiments. The specific fabrication method of this micro / nano structure refers to the above embodiments. Since the specific fabrication method of the micro / nano structure adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be elaborated further here.

[0083] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A photolithography medium for fabricating micro / nano structures, characterized in that, The micro / nano structure includes a substrate and a patterned layer on the substrate. The patterned layer is formed by the photolithography medium, which is made of thermal photoresist, specifically PPC. The photolithography medium is formed from a PPC solution with a concentration of 6.5%.

2. The photolithography medium as described in claim 1, characterized in that, The PPC solution is formed by dissolving PPC solid particles in anisole solvent.

3. The photolithography medium as described in claim 2, characterized in that, The thickness of the thermal photoresist is between 250 nm and 300 nm.

4. The photolithography medium as described in claim 3, characterized in that, The thermal decomposition temperature of the thermal photoresist is greater than 300℃.

5. A method for preparing micro / nano structures, comprising the following steps: Drop the prepared PPC solution onto the substrate surface; A PPC film is formed on the substrate by a spin coating process to form a thermal photoresist. and A cutout pattern is etched on the thermal photoresist to form a pattern layer on the substrate.

6. The method as described in claim 5, characterized in that, The concentration of the PPC solution is 6.5%.

7. The method as described in claim 5 or 6, characterized in that, The etching of a cutout pattern on the photoresist film to form a pattern layer on the substrate includes: An array pattern is etched onto the photoresist film using a thermal probe; and The hollow pattern is etched onto the array pattern using a plasma processing method to form the pattern layer on the substrate.

8. The method as described in claim 7, characterized in that, The method of etching the hollow pattern on the array pattern using a plasma processing method to form a pattern layer on the substrate includes: The array pattern is etched multiple times in a short period of time using a plasma treatment method to form the hollow pattern, and the pattern layer is formed on the substrate.

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