Direct patterning method of two-dimensional material

Abstract

The invention relates to a direct patterning method of a two-dimensional material, which comprises the following steps of: aligning and loading a quartz mask with a metal pattern layer and a substrate on which the two-dimensional material is uniformly distributed to obtain a substrate-mask assembly; ultraviolet light is utilized to excite oxygen to generate ozone to etch the substrate-mask assembly, and then direct patterning of the two-dimensional material is completed. The invention provides a direct patterning solution which can be compatible with an existing semiconductor production line and is suitable for various two-dimensional material systems, and a reliable process basis is provided for application of two-dimensional materials in high-performance electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, and specifically relates to a method for direct patterning of two-dimensional materials. Background Technology

[0002] Two-dimensional materials (such as graphene and molybdenum disulfide, MoS2) possess atomic-level thickness and excellent electrical properties, making them ideal candidates for breaking through the physical limits of traditional silicon-based semiconductors and continuing Moore's Law. These materials hold promise for application in chips manufactured using more advanced processes (such as sub-1 nanometer scale), bringing higher computing performance and lower power consumption to electronic devices.

[0003] Patterning of two-dimensional (2D) materials refers to the process of precisely defining and fabricating specific geometric shapes and structures on 2D materials, and is a key step in device fabrication. Currently, 2D material patterning largely draws upon traditional semiconductor microelectronics processing techniques, and can be mainly divided into two categories: "top-down" and "bottom-up." The "top-down" method involves first preparing a large-area, uniform 2D material film, and then removing some material using subtractive processing techniques, leaving the desired pattern. This type of method mainly includes photolithography and etching, electron beam writing, and laser writing / ablation. The "bottom-up" method refers to directly generating the patterned structure during the 2D material fabrication process, rather than fabricating first and then processing. Before growth, a specific patterned structure (such as a metal catalyst pattern or a stepped substrate) is prepared on a substrate, and then methods such as CVD are used to allow the 2D material to grow epitaxially only in the specific patterned area. This method avoids the etching and transfer steps that are unavoidable in the patterning process of "top-down" methods, reducing damage and contamination of the 2D material from the source.

[0004] However, current patterning technology remains a key challenge limiting the industrial application of two-dimensional (2D) material electronic devices. Traditional patterning methods, especially photoresist-based "top-down" techniques, while mature in process, suffer from inherent problems such as polymer residue, chemical contamination, and physical damage, fundamentally contradicting the extreme sensitivity of 2D materials to surfaces and interfaces. This results in devices with performance often far below theoretical values, severely hindering the application of 2D materials in high-performance electronic devices. Laser direct writing technology, while eliminating the need for photoresist and avoiding contamination, suffers from relatively low processing efficiency, potential thermal damage, and limited resolution, making it difficult to meet the demands of wafer-level mass production. "Bottom-up" 2D material patterning technology based on pre-patterned substrate-assisted growth heavily relies on the substrate's surface morphology and catalytic activity. The growth boundaries are difficult to control precisely, potentially leading to polycrystalline or non-uniform growth. The material quality grown at the pattern edges may be lower than that of continuous films, resulting in poor versatility. Therefore, it is necessary to develop a photoresist-free direct patterning technology for 2D materials.

[0005] In existing technologies, Y Tu et al. (Tu Y, Utsunomiya T, Ichii T, et al. Vacuum-Ultraviolet Promoted Oxidative Micro Photoetching of Graphene Oxide[J].ACS Applied Materials & Interfaces, 2016:acsami.6b00994.DOI:10.1021 / acsami.6b00994.) proposed using vacuum ultraviolet light (VUV) to promote graphene oxidation micro-etching to achieve patterning. However, they used a 300nm thick Cr as a spacer layer, which has a 200nm height difference with the 100nm thick pattern layer. This height difference forms a "step"-shaped cavity, resulting in uneven gas diffusion, disrupting the uniform flow and distribution of gas in the narrow space between the mask and the substrate, leading to uneven active oxygen concentration, which in turn causes inconsistent etching rates, resulting in a decrease in the uniformity and fidelity of the pattern. Furthermore, it relies on a vacuum environment, requiring the installation of a vacuum chamber and a pressure control system, which increases the complexity of the equipment and the cost of manufacturing processes.

[0006] H Yue et al. (Yue H, Tao H, Wu Y, et al. Exploring the working mechanism of graphene patterning by magnetic-assisted UV ozonation[J]. PhysicalChemistry Chemical Physics, 2017, 19.DOI:10.1039 / C7CP03523C.) proposed using a cutout mask combined with magnetic-assisted UV ozone etching to achieve adhesive-free and substrate-free patterning. However, this method suffers from inherent lateral over-oxidation at the micrometer level (3-4 µm), which cannot completely eliminate edge diffusion and limits the ultimate precision of the pattern. Furthermore, this method relies entirely on customized physical cutout masks, resulting in poor process flexibility and difficulty in fabricating complex patterns, such as circles, rectangles, and polygons required for devices. These factors collectively limit its application potential in the field of nanoelectronics, which requires high precision, high flexibility, and complex integration.

[0007] Zhang et al. (Zhang L, Diao S, Nie Y, et al. Photocatalytic Patterning and Modification of Graphene[J]. Journal of the American Chemical Society, 2011, 133(8):2706-2713.DOI:10.1021 / ja109934b.) proposed a wet, pollution-free patterning technique for graphene using TiO2 photocatalysis to generate -OH radicals. However, this technique has significant limitations: its reaction rate is heavily dependent on the oxygen concentration and humidity in the environment, and the optimal reaction conditions (approximately 50% relative humidity) have a narrow window, resulting in poor process controllability. Most importantly, this photocatalytic oxidation process generates a mixture of serrated and armchair-shaped edges, making it impossible to achieve atomic-level precise control over the graphene edge structure; furthermore, the photocatalytic oxidation process is very slow, resulting in a very slow etching rate, which limits its application in high-performance electronic devices.

[0008] Therefore, how to provide a high-precision and simple-to-operate method for patterning two-dimensional materials is an urgent technical problem to be solved. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a direct patterning method for two-dimensional materials, so as to solve the problems of complex equipment, poor etching uniformity, significant lateral diffusion, inaccurate edge control and insufficient process flexibility that are common in the prior art.

[0010] This invention provides a method for direct patterning of two-dimensional materials, comprising the following steps:

[0011] A quartz mask with a metallic patterned layer is aligned and mounted with a substrate on which two-dimensional material is uniformly distributed to obtain a substrate-mask assembly. Ozone generated by ultraviolet light is used to etch the substrate-mask assembly, thus completing the direct patterning of the two-dimensional material.

[0012] The direct patterning method provided by this invention operates under ambient pressure, avoiding complex vacuum systems and significantly reducing equipment costs and process complexity. Simultaneously, this invention utilizes a highly efficient dry chemical etching mechanism, eliminating the need for photocatalytic reactions, thereby significantly accelerating the etching rate, reducing sensitivity to oxygen concentration and humidity, widening the process window, and achieving more precise control over the edge structure of graphene, meeting the atomic-level precision requirements of high-performance electronic devices.

[0013] Preferably, the metal in the metal pattern layer is chromium, gold, or platinum.

[0014] This invention utilizes a quartz mask with a metal patterned layer, which not only offers excellent pattern flexibility, enabling efficient fabrication of highly complex micro / nano structures (such as circles, rectangles, and polygons), but also fundamentally reduces the problem of lateral over-etching at the micrometer level, thereby achieving higher edge precision and pattern fidelity. This invention achieves spatially selective transmission of ultraviolet light through the quartz mask with the metal patterned layer, thereby controlling ozone generation and the oxidation etching areas of two-dimensional materials. Finally, patterning is completed under ambient pressure, low temperature, and without the need for photoresist and physical etching. This method combines the high precision of a top-down approach with the low-damage advantages of a bottom-up approach, making it suitable for wafer-level two-dimensional material device fabrication.

[0015] Preferably, the two-dimensional material is MoS2 or graphene, more preferably MoS2.

[0016] This invention employs a direct contact method between the metal pattern layer and the two-dimensional material, eliminating the gas flow disturbance problem caused by the height difference between the mask and the substrate in the prior art, thereby effectively suppressing lateral etching and improving pattern resolution and uniformity.

[0017] Preferably, the substrate is a silicon substrate.

[0018] Preferably, the dominant wavelength of the ultraviolet light is 254 nm.

[0019] Preferably, the etching temperature is 50-80℃ and the etching time is 90-120 min.

[0020] In the etching process of this invention, ultraviolet light excites oxygen to generate ozone, and the generated oxygen free radicals diffuse to the surface of the two-dimensional material, oxidizing the C or S elements therein into gaseous products and expelling them with the airflow, while the graphene in the area blocked by the quartz mask is retained.

[0021] Preferably, the ventilation system is activated simultaneously with the etching process, and the ventilation system has an air velocity of 20-30 m / s. 3 / h.

[0022] The present invention also provides a patterned two-dimensional material prepared by a direct patterning method.

[0023] Beneficial effects

[0024] This invention utilizes selective oxidation of ultraviolet ozone under patterned control of a quartz mask's metal layer. By combining physical blocking and chemical inhibition of the reaction between ultraviolet light and ozone in the mask's transparent and non-transparent areas, it achieves high-precision, low-damage, and high-efficiency patterning of two-dimensional materials under ambient pressure, low temperature, without photoresist or wet etching agents. This avoids the problems of traditional photoresist residue, wet etching contamination, and laser thermal damage. By avoiding the use of any organic photoresist and wet etching solution, this invention fundamentally eliminates polymer residue and surface contamination, ensuring the intrinsic cleanliness of the two-dimensional material surface. Furthermore, the metal layer pattern in this invention can be fabricated to the micro-nano scale using conventional photolithography processes, thereby enabling high-resolution two-dimensional material pattern definition with micron-level precision. Secondly, the ultraviolet ozone treatment in this invention can be carried out at normal pressure and low temperature, and can process the entire wafer in parallel to meet the needs of mass production. The operation method is simple, and the resulting pattern has clear boundaries and a clean surface, which helps to realize two-dimensional material devices with higher mobility and lower contact resistance, and provides a reliable process basis for the application of two-dimensional materials in high-performance electronic devices. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the direct patterning method of the present invention.

[0026] Figure 2 This is an optical photograph of the product obtained in Example 1.

[0027] Figure 3 The image shown is a SEM characterization image of the product obtained in Example 2.

[0028] Figure 4 The image shown is a SEM characterization image of the product obtained in Example 3.

[0029] Figure 5 The image shown is a SEM characterization image of the product obtained in Example 4. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels;

[0033] In this embodiment of the invention, the quartz mask includes a light-transmitting quartz region and an opaque metal layer pattern region, wherein the grooves of the metal layer pattern region are 50-200 nm.

[0034] In this embodiment of the invention, the metal layer on the mask is a chromium metal layer.

[0035] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0036] Example 1

[0037] This embodiment provides a direct patterning method for molybdenum disulfide (MoS2) arrays, such as... Figure 1 As shown, it includes the following steps:

[0038] (1) Sample preparation: Provide a 4-inch SiO2 / Si substrate with a clean surface and covered with a few layers of molybdenum disulfide (MoS2) two-dimensional material, and prepare a clean rectangular array quartz mask.

[0039] (2) Alignment and Loading: The MoS2 substrate is fixed to the sample stage by vacuum adsorption, and the mask is mounted on a three-dimensionally adjustable mask device. Observation and fine-tuning are performed using an optical microscope to ensure complete alignment of the substrate and the crosshairs on the mask, achieving micron-level alignment accuracy. Figure 1 As shown, quartz glass, a metal layer, a two-dimensional material, and a substrate are stacked sequentially, and the patterned area of ​​the metal layer on the mask is directly attached to the two-dimensional material. There is a gap between the quartz glass and the two-dimensional material, and this gap, together with the metal layer, constitutes a spatial structure.

[0040] (3) Ultraviolet ozone etching: The aligned substrate-mask assembly is smoothly placed into the sample chamber of the ultraviolet ozone etching apparatus. The chamber door is closed to ensure a seal, allowing ozone and oxygen to enter the spatial structure formed between the quartz glass and the two-dimensional material, and between the metal layer and the quartz glass. The substrate heating device is turned on, and the temperature is set to 80℃. The ultraviolet light source (main wavelength of 254 nm) is turned on for irradiation, and the exhaust system is turned on (wind speed set to 20 m). 3 The reaction time is 120 minutes ( / h). During this process, oxygen free radicals generated by ultraviolet light excitation diffuse to the surface of MoS2, oxidize them into gaseous products such as SO2 / SO3, and are discharged with the gas flow, while the MoS2 in the mask metal pattern layer-masked area is retained.

[0041] (4) Sampling and Testing: After the procedure is completed, the ultraviolet light source is turned off, and the sample is removed after the chamber has cooled down. The results are observed using an optical microscope as follows: Figure 2 As shown, a clear MoS2 array pattern was successfully obtained on the substrate, with a linewidth of approximately 15.9 ± 1.2 μm.

[0042] Example 2

[0043] This embodiment provides a direct patterning method for graphene rectangular arrays, including the following steps:

[0044] (1) Sample preparation: Provide a 4-inch SiO2 / Si substrate with a clean surface and uniformly distributed graphene two-dimensional material, and prepare a rectangular array of quartz masks with a clean surface.

[0045] (2) Alignment and Loading: The graphene substrate is fixed to the sample stage by vacuum adsorption, and the mask is mounted on a three-dimensionally adjustable mask device. Observation and fine-tuning are performed using an optical microscope to ensure complete alignment of the substrate and the crosshairs on the mask, achieving micron-level alignment accuracy. Figure 1 As shown, quartz glass, a metal layer, a two-dimensional material, and a substrate are stacked sequentially, and the patterned area of ​​the metal layer on the mask is directly attached to the two-dimensional material. There is a gap between the quartz glass and the two-dimensional material, and together with the metal layer, they form a spatial structure.

[0046] (3) Ultraviolet ozone etching: The aligned substrate-mask assembly is smoothly placed into the sample chamber of the ultraviolet ozone etching apparatus. The chamber door is closed to ensure a seal, allowing ozone and oxygen to enter the spatial structure formed between the quartz glass and the two-dimensional material, and between the metal layer and the quartz glass. The substrate heating device is turned on, and the temperature is set to 50°C. The ultraviolet light source (main wavelength 254 nm) is turned on for irradiation, and the exhaust system is turned on (wind speed set to 20 m). 3 The reaction time is 90 minutes ( / h). During this process, oxygen free radicals generated by ultraviolet light excitation diffuse to the graphene surface, oxidize them into gaseous products such as CO / CO2, and are discharged with the gas flow, while the graphene in the area blocked by the mask metal pattern layer is retained.

[0047] (4) Sampling and Testing: After the procedure is completed, turn off the ultraviolet light source and remove the sample after the chamber has cooled down. Observe the sample using a scanning electron microscope (SEM). The results are as follows: Figure 3 As shown, the array pattern of the mask was successfully replicated on the graphene, with clear edges. The remaining graphene was completely etched clean, with no obvious contamination. The linewidth was approximately 15.7 ± 1.3 μm.

[0048] Example 3

[0049] This embodiment provides a method for patterning complex graphene shapes, including the following steps:

[0050] (1) Sample preparation: Provide a 4-inch graphene / SiO2 / Si substrate identical to that in Example 2, and prepare a clean mask with a “U-shaped” array.

[0051] (2) Alignment and loading: Fix the graphene substrate on the sample stage by vacuum adsorption, and install the mask on a three-dimensionally adjustable mask device. Observe and finely adjust through an optical microscope to make the cross alignment marks on the substrate and the mask completely coincide, achieving a micron-level alignment accuracy. As Figure 1 shown, the quartz glass, metal layer, two-dimensional material, and substrate are stacked in sequence, and the metal layer pattern area on the mask is directly adhered to the two-dimensional material. There is a gap between the quartz glass and the two-dimensional material, and they together form a spatial structure with the metal layer.

[0052] (3) UV ozone etching: Steadily place the aligned substrate-mask assembly into the sample chamber of the UV ozone etching device, close the chamber door to ensure sealing, and allow ozone and oxygen to enter the spatial structures formed between the quartz glass and the two-dimensional material, and between the metal layer and the quartz glass. Turn on the substrate heating device and set the temperature to 50 °C. Turn on the UV light source (main wavelength is 254 nm) for irradiation, and at the same time turn on the exhaust system (wind speed is set to 20 m 3 / h), and the reaction time is 90 minutes. During this process, the oxygen radicals generated by the UV light exciting oxygen diffuse to the graphene surface, oxidize it into gaseous products such as CO / CO2 and are discharged with the air flow, while the graphene in the area blocked by the mask metal pattern layer is retained.

[0053] (4) Sampling and inspection: Take out the sample after the program ends. Detect it using SEM, and the result is as Figure 4 shown. It can be seen that the "square frame" pattern on the graphene is replicated with high fidelity, the pattern edges are sharp, the corners are clear, there are no defects such as broken lines, and the line width is about 5.9 ± 1.1 μm. It proves that this process also has excellent processing capabilities for complex graphic structures.

[0054] Example 4

[0055] This example provides a method for patterning molybdenum disulfide (MoS2) with complex patterns, including the following steps:

[0056] (1) Sample preparation: Provide a 4-inch graphene / SiO2 / Si substrate same as in Example 1. Prepare a mask with a clean surface and a "butterfly" shape.

[0057] (2) Alignment and loading: Fix the MoS2 substrate on the sample stage by vacuum adsorption, and install the mask on a three-dimensionally adjustable mask device. Observe and finely adjust through an optical microscope to make the cross alignment marks on the substrate and the mask completely coincide, achieving a micron-level alignment accuracy. As Figure 1 shown, the quartz glass, metal layer, two-dimensional material, and substrate are stacked in sequence, and the metal layer pattern area on the mask is directly adhered to the two-dimensional material. There is a gap between the quartz glass and the two-dimensional material, and they together form a spatial structure with the metal layer.

[0058] (3) Ultraviolet ozone etching: The aligned substrate-mask assembly is smoothly placed into the sample chamber of the ultraviolet ozone etching apparatus. The chamber door is closed to ensure a seal, allowing ozone and oxygen to enter the spatial structure formed between the quartz glass and the two-dimensional material, and between the metal layer and the quartz glass. The substrate heating device is turned on, and the temperature is set to 80℃. The ultraviolet light source (main wavelength of 254 nm) is turned on for irradiation, and the exhaust system is turned on (wind speed set to 20 m). 3 The reaction time is 90 minutes ( / h). During this process, oxygen free radicals generated by ultraviolet light excitation diffuse to the surface of MoS2, oxidize them into gaseous products such as SO2 / SO3, and are discharged with the gas flow, while the MoS2 in the area blocked by the mask metal pattern layer is retained.

[0059] (4) Sampling and Testing: After the procedure is completed, the ultraviolet light source is turned off, and the sample is removed after the chamber has cooled down. The results are observed using an optical microscope as follows: Figure 5 As shown, a clear MoS2 complex pattern was successfully obtained on the substrate.

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for direct patterning of two-dimensional materials, characterized in that, Includes the following steps: A quartz mask with a metallic patterned layer is aligned and mounted with a substrate on which two-dimensional material is uniformly distributed to obtain a substrate-mask assembly. Ozone generated by ultraviolet light is used to etch the substrate-mask assembly, thus completing the direct patterning of the two-dimensional material.

2. The direct patterning method according to claim 1, characterized in that, The metal in the metal pattern layer is chromium, gold, or platinum.

3. The direct patterning method according to claim 1, characterized in that, The two-dimensional material is MoS2 or graphene.

4. The direct patterning method according to claim 1, characterized in that, The substrate is a silicon substrate.

5. The direct patterning method according to claim 1, characterized in that, The dominant wavelength of the ultraviolet light is 254 nm.

6. The direct patterning method according to claim 1, characterized in that, The etching temperature is 50-80℃ and the etching time is 90-120 min.

7. The direct patterning method according to claim 1 or 6, characterized in that, The etching process is performed simultaneously with the activation of the exhaust system, which has an airflow velocity of 20-30 m / s. 3 / h.

8. A patterned two-dimensional material prepared by the direct patterning method as described in any one of claims 1 to 7.

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