Soft nanoimprint-based TMDC material patterning method

Abstract

A soft nanoimprint-based TMDC material patterning method. Adjusting a SF6 gas etching time on the basis of the thickness of a TMDC two-dimensional material can freely adjust a nano pattern depth to adapt to different optical performance requirements. The present invention specifically optimizes an RIE electron beam lithography process to prepare large-area samples, can implement full-area patterning of TMDC two-dimensional materials, greatly optimizes a technological process, improves scientific research production efficiency, and reduces process costs. During integration with a photoelectric device, when a silicon oxide wafer is used as a substrate, O2 is first introduced 5s into an RIE plasma etcher to treat the surface of the silicon oxide wafer so as to increase its hydrophilicity, thereby allowing for more uniform spin-coating of SU8. The method is universal to TMDC of different thicknesses and types.

Description

Patterning method for TMDC materials based on soft nanoimprinting Technical Field

[0001] This invention relates to the field of two-dimensional material transfer (TMDC two-dimensional material patterning) technology, and specifically to a TMDC material patterning method based on soft nanoimprinting. Background Technology

[0002] Currently, the most common method for patterning two-dimensional materials in TMDC (Technical Data Conversion) is electron beam lithography (EBL), a high-precision micro / nano fabrication technique that can create complex structures and devices at the nanoscale. Its basic principle is to use an electron beam to locally expose the surface of a photosensitive material, and then remove the unexposed areas using methods such as chemical etching or physical etching, thereby forming the desired structure. The EBL process includes the following steps:

[0003] First, the photosensitive material is prepared. EBL technology requires a photosensitive material as the processing object, typically a polymer or metal film. Before processing, the photosensitive material needs to undergo surface treatment to improve its surface smoothness and adhesion. Second, a mask is designed and fabricated. EBL technology uses a mask to control the exposure area of ​​the electron beam. The mask can be designed using computer-aided design (CAD) software and fabricated using electron beam etching or photolithography. Finally, exposure is performed by placing the mask on the surface of the photosensitive material and using an electron beam for localized exposure.

[0004] Although EBL has advantages such as high resolution, high precision, and high controllability, it suffers from high cost and small pattern area in practical scientific research, which cannot meet the needs of daily experiments. Therefore, there is an urgent need for a new method. Summary of the Invention

[0005] The main innovation of this invention lies in the use of soft nanoimprinting technology in the patterning of TMDC two-dimensional materials, and the targeted optimization of the process to achieve low-cost, large-area sample preparation. This solves the problems of high experimental costs and small pattern area, facilitating subsequent integration of silicon-based devices and fabrication of flat-panel optical devices. This method, through soft nanoimprinting, can obtain large-area, high-quality patterned TMDC two-dimensional materials, significantly reducing patterning costs. Furthermore, this method boasts high platform compatibility and good alignment with existing research on two-dimensional materials, devices, and processes.

[0006] The patterning method for TMDC materials based on soft nanoimprinting includes the following steps:

[0007] Step 1: Cut the polydimethylsiloxane (PDMS) film to size and attach it to a glass slide to form a PDMS / glass slide structure;

[0008] Step 2: The transition metal sulfide TMDC two-dimensional material is transferred to the PDMS film using a mechanical peeling method. The peripheral irrelevant PDMS film is removed by cutting with a blade to reduce the PDMS area attached to the glass slide, forming a TMDC / PDMS / glass slide structure.

[0009] Step 3: The TMDC / PDMS / glass slide structure is transferred to the target substrate using a dry transfer method. The TMDC / PDMS / glass slide is fixed in the substrate slot of the transfer platform, and the target substrate is fixed to the sample stage using hot melt adhesive to form the TMDC / substrate structure.

[0010] Step 4: Use a spin coater to spin coat a layer of SU8 film onto the TMDC / substrate, and heat it to form an SU8 film / TMDC / substrate structure;

[0011] Step 5: Prepare the stamp by transferring the nanoarray pattern onto the SU8 thin film / TMDC / substrate through nanoimprinting, thus forming a patterned SU8 thin film / TMDC / substrate structure.

[0012] Step 6: Use RIE plasma etching to pattern the SU8 thin film / TMDC / substrate to finally obtain the target patterned TMDC / substrate structure.

[0013] The beneficial effects achieved by this invention are as follows:

[0014] (1) This method utilizes soft nanoimprinting technology and RIE etching process to achieve patterned preparation of TMDC two-dimensional materials, while ensuring the accuracy of the nanostructure.

[0015] (2) This method adjusts the SF6 gas etching time according to the thickness of the TMDC two-dimensional material, which can freely control the depth of the nanopattern and achieve the adaptation of different optical performance requirements.

[0016] (3) This method specifically optimizes the RIE electron beam etching process to achieve large-area sample preparation, enabling full-area patterning of TMDC two-dimensional materials. The sample preparation depends on the size of the mechanically exfoliated TMDC two-dimensional material, which can generally reach tens of micrometers.

[0017] (4) The method used in this study greatly optimizes the process, improves scientific research and production efficiency, and reduces process costs. As long as the stamp is not damaged during use, it can be used repeatedly, which greatly saves sample preparation costs.

[0018] (5) When integrated with optoelectronic devices, TMDC two-dimensional materials generally require silicon oxide wafers as substrates before subsequent processes. In this method, when silicon oxide wafers are used as substrates, the surface of silicon oxide wafers needs to be treated by passing O25s through a RIE plasma etching machine. This can increase its hydrophilicity and make the SU8 spin coating more uniform.

[0019] (6) This method is universally applicable to TMDCs of different thicknesses and types. Attached Figure Description

[0020] Figure 1 is a flowchart of the method in an embodiment of the present invention.

[0021] Figure 2 shows the reverse structure of the seal in an embodiment of the present invention.

[0022] Figure 3 is a flowchart of the soft nanoimprinting process in an embodiment of the present invention.

[0023] Figure 4 is a 100× optical microscope image of the MoS2 material transferred to the silicon oxide substrate in Example 1.

[0024] Figure 5 is a 100× optical microscope image of the MoS2 material after patterning (pillars) in Example 1.

[0025] Figure 6 is a 100×SEM image of the MoS2 material after patterning (pillars) in Example 1.

[0026] Figure 7 is a 100× optical microscope image of the MoS2 material transferred to the silicon oxide substrate in Example 2.

[0027] Figure 8 is a 100× optical microscope image of the MoS2 material after patterning (holes) in Example 2.

[0028] Figure 9 is a 100×SEM image of the MoS2 material after patterning (holes) in Example 2.

[0029] Figure 10 is a 100× optical microscope image of the MoS2 material transferred to a quartz substrate in Example 3.

[0030] Figure 11 is a 100× optical microscope image of the MoS2 material after patterning (pillars) in Example 3.

[0031] Figure 12 is a 100×SEM image of the MoS2 material after patterning (pillars) in Example 4.

[0032] Figure 13 is a 100× optical microscope image of the MoS2 material transferred to a quartz substrate in Example 4.

[0033] Figure 14 is a 100× optical microscope image of the MoS2 material after patterning (holes) in Example 4.

[0034] Figure 15 is a 100×SEM image of the MoS2 material after patterning (holes) in Example 4. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Example 1 uses MoS2 as the etching material, silicon dioxide (Si / SiO2) as the substrate, and a pillar structure as the stamp.

[0037] Step 1: Cut the commercial PDMS film into strips approximately 0.8cm × 2cm in size and attach them to a glass slide that has been wiped clean with ethanol. Treat the slide with ozone for 5 minutes to reduce the surface stickiness of the PDMS, making it easier to transfer the MoS2 that will be mechanically peeled off onto the slide to the substrate in subsequent processes.

[0038] Step 2: Using a mechanical peeling method, the TMDC two-dimensional material is transferred onto the PDMS film using blue adhesive tape. An optical microscope is used to roughly locate the MoS2 material with suitable shape and color under a 10× eyepiece. The microscope is then switched to 100× for detailed observation to check whether the thickness is uniform and flat. After selection, an irrelevant PDMS film is removed by cutting with a blade to further reduce the PDMS area attached to the glass slide, making it easier to find the target MoS2 material in the CCD field of view on the transfer platform in subsequent processes.

[0039] Step 3: Using a dry transfer method, the MoS2 material on the TMDC is controllably and precisely transferred to the target silicon oxide wafer via a transfer platform. The MoS2 material / PDMS / glass slide prepared in the previous step is fixed in the substrate slot of the transfer platform. The target MoS2 material on the small PDMS film on the glass slide is located by CCD imaging. It is aligned with a clean area on the silicon oxide substrate fixed to the sample stage with hot melt adhesive. The electric displacement platform is controlled to slowly lower the MoS2 material / PDMS / glass slide until it adheres to the silicon oxide substrate. Wait 3-5 minutes to allow the target MoS2 material to better adhere to the silicon oxide wafer (because the PDMS film was treated with ozone in step 1, the adhesion of the PDMS film will be less than that of the silicon oxide wafer). Finally, the electric displacement platform is controlled to slowly lift the MoS2 material / PDMS / glass slide to complete the transfer of the MoS2 material. The purpose of this step is to obtain a relatively clean MoS2 material / silicon oxide wafer structure and avoid too much unacceptable defective MoS2 material around the target MoS2 material, which would affect the spin coating of SU8 in the subsequent process.

[0040] For the target silicon oxide wafer, the silicon oxide wafer (oxide layer 285nm) is cut into 1cm×1cm squares, placed in a RIE, and O2 is introduced at a gas flow rate of 50sccm, power of 30W, high valve setting of 100, and duration of 5s. This pretreatment increases the hydrophilicity of the silicon oxide wafer surface, making the SU8 spin coating more uniform in subsequent processes.

[0041] Step 4: Design the structural template stamp according to the specific experimental objectives. The nanoarray pattern used for the stamp consists of holes and pillars, which are inverse structures. For example, the period of a hole stamp is the same as the period of a pillar stamp, and the diameter of the hole is the same as the diameter of the pillar. When the two are stacked together, the nanoarray pattern can be perfectly aligned, as shown in Figure 2. In this embodiment, a single micro-nano pillar structure with a height of 50 nm, a diameter of 600 nm, and a period of 1200 nm was designed. The stamp corresponding to this micro-nano structure was prepared using polydimethylsiloxane (PDMS) material. As long as the stamp is not damaged during use, it can be repeatedly pressed, greatly saving sample preparation costs.

[0042] Step 5: Place the MoS2 material / silicon oxide wafer on the sample stage of the spin coater, and drop 2-3 drops of SU8 photoresist solution with a mass concentration ratio of 1:1 onto its surface. Spin coat the wafer at a spin speed of 4000 r / min, an acceleration of 500 r / s, and a spin coating time of 30 s. After spin coating, place the wafer on a 65°C hot stage for 1 min, then on a 95°C hot stage for 1 min. After cooling to room temperature, press the micro / nano structure stamp onto the wafer and place it on a 95°C hot stage for 45 s. After cooling to room temperature, remove the micro / nano structure stamp to obtain the patterned SU8 / MoS2 material / silicon oxide wafer.

[0043] Step 6: Place the patterned MoS2 material / silicon oxide wafer into a RIE electron beam etching machine. First, introduce O2 with a flow rate of 50 sccm, power of 30W, high valve set to 100, and etching time of 250 seconds. Under these conditions, etch a portion of the SU8 photoresist to expose the MoS2 material, creating an opening. Second, introduce SF6 with a flow rate of 15 sccm, power of 30W, high valve set to 100, and etching time of 150 seconds. Under these conditions, further etch the exposed MoS2 material. The etching depth can be adjusted by changing the etching time as needed. Third, introduce O2 again with a flow rate of 100 sccm, power of 100W, high valve set to 100, and etching time of 360 seconds. Under these conditions, remove the remaining SU8 photoresist to form the final patterned MoS2 material / silicon oxide wafer.

[0044] Example 2 uses MoS2 as the etching material, silicon dioxide (Si / SiO2) as the substrate, and a porous structure as the stamp. This example differs from Example 1 only in the use of a porous stamp (porosity of 50nm, diameter of 620nm, and period of 1100nm) in step 4 and the specific parameters in step 6. The corresponding steps and processes are the same as in Example 1. The specific parameters for step 6 in this example are:

[0045] The patterned MoS2 material / silicon oxide wafer is placed in a RIE electron beam etching machine. The first step involves introducing O2 at a flow rate of 50 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 120 s. Under these conditions, a portion of the SU8 photoresist is etched to expose the MoS2 material, creating what is known as an opening. The second step involves introducing SF6 at a flow rate of 15 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 100 s. Under these conditions, further etching is performed on the exposed MoS2 material. The etching depth can be further adjusted by controlling the etching time as needed. The third step involves introducing O2 again at a flow rate of 100 sccm, a power of 100 W, a high valve setting of 100, and an etching time of 360 s. Under these conditions, the remaining SU8 photoresist is removed, forming the final patterned MoS2 material / silicon oxide wafer.

[0046] Example 3 uses MoS2 as the etching material, quartz as the substrate, and a pillar structure as the stamp. This example differs from Example 1 only in the substrate material (quartz), the stamp structure parameters used in step 4 (pillar structure height 50nm, diameter 650nm, period 1200nm), and the specific parameters in step 6. The corresponding steps and processes are the same as in Example 1. The specific parameters for step 6 in this example are:

[0047] The patterned MoS2 material / quartz wafer is placed in a RIE electron beam etching machine. The first step involves introducing O2 at a flow rate of 50 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 200 s. Under these conditions, a portion of the SU8 photoresist is etched to expose the MoS2 material, creating what is known as an opening. The second step involves introducing SF6 at a flow rate of 15 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 120 s. Under these conditions, further etching is performed on the exposed MoS2 material. The etching depth can be further adjusted by controlling the etching time as needed. The third step involves introducing O2 again at a flow rate of 100 sccm, a power of 100 W, a high valve setting of 100, and an etching time of 360 s. Under these conditions, the remaining SU8 photoresist is removed, forming the final patterned MoS2 material / quartz wafer.

[0048] Example 4 uses MoS2 as the etching material, quartz as the substrate, and a porous structure as the stamp. This example differs from Example 1 only in the substrate material (quartz), the use of a porous stamp in step 4 (the porous structure has a height of 50 nm, a diameter of 650 nm, and a period of 1300 nm), and the specific parameters in step 6. The corresponding steps and processes are the same as in Example 1. The specific parameters for step 6 in this example are:

[0049] The patterned MoS2 material / quartz wafer is placed in a RIE electron beam etching machine. The first step involves introducing O2 at a flow rate of 50 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 120 s. Under these conditions, a portion of the SU8 photoresist is etched to expose the MoS2 material, creating what is known as an opening. The second step involves introducing SF6 at a flow rate of 15 sccm, a power of 30 W, a high valve setting of 100, and an etching time of 220 s. Under these conditions, the exposed MoS2 material is further etched, and the etching depth can be adjusted according to requirements via the etching time. The third step involves introducing O2 again at a flow rate of 100 sccm, a power of 100 W, a high valve setting of 100, and an etching time of 360 s. Under these conditions, the remaining SU8 photoresist is removed, forming the final patterned MoS2 material / quartz wafer.

[0050] The above four embodiments demonstrate that this method can successfully and cost-effectively pattern TMDC materials on different substrates over a large area, and has a certain degree of universality in this technical field.

[0051] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A method for patterning TMDC materials based on soft nanoimprinting, characterized in that: The method includes the following steps: Step 1: Cut the polydimethylsiloxane (PDMS) film to size and attach it to a glass slide to form a PDMS / glass slide structure; Step 2: The transition metal sulfide TMDC two-dimensional material is transferred to the PDMS film using a mechanical peeling method. The peripheral irrelevant PDMS film is removed by cutting with a blade to reduce the PDMS area attached to the glass slide, forming a TMDC / PDMS / glass slide structure. Step 3: The TMDC / PDMS / glass slide structure is transferred to the target substrate using a dry transfer method. The TMDC / PDMS / glass slide is fixed in the substrate slot of the transfer platform, and the target substrate is fixed to the sample stage using hot melt adhesive to form the TMDC / substrate structure. Step 4: Use a spin coater to spin coat a layer of SU8 film onto the TMDC / substrate, and heat it to form an SU8 film / TMDC / substrate structure; Step 5: Prepare the stamp by transferring the nanoarray pattern onto the SU8 thin film / TMDC / substrate through nanoimprinting, thus forming a patterned SU8 thin film / TMDC / substrate structure. Step 6: Use RIE plasma etching to pattern the SU8 thin film / TMDC / substrate to finally obtain the target patterned TMDC / substrate structure.

2. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 1, the polydimethylsiloxane (PDMS) film is cut into strips approximately 0.8 cm × 2 cm in size.

3. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 1, the PDMS film is treated with ozone for 5 minutes to reduce the surface stickiness of the PDMS.

4. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 2, the TMDC material used is MoS2, WS2, MoSe2 or WSe2 with a certain number of layers and thickness, approximately 10nm-250nm.

5. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 3, the substrate used is quartz, pure silicon wafer, or silicon oxide wafer.

6. The method for patterning TMDC materials based on soft nanoimprinting according to claim 5, characterized in that: In step 3, an O2 treatment is performed on the substrate surface using a RIE plasma etching machine to increase its hydrophilicity.

7. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 4, the heating step includes heating on a 60°C hot plate for 1 minute, and then heating on a 90°C hot plate for 1 minute.

8. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: In step 5, the stamp nanoarray pattern used consists of holes and pillars, which are inverse structures of each other. The diameter of a single structure is 500nm-750nm, and the period is 1000nm-1300nm.

9. The method for patterning TMDC materials based on soft nanoimprinting according to claim 1, characterized in that: Step 6, the RIE plasma etching patterning process is specifically divided into three steps: Step 6-1: Introduce O2 at a flow rate of 50 sccm, power of 30W, high valve setting of 100, and etching time of 120S. Under these conditions, etch part of the SU8 photoresist to expose the TMDC and complete the opening. Step 6-2: Introduce SF6 at a flow rate of 15 sccm, power of 30W, and high valve setting of 100. Adjust the duration of this step according to the thickness of the TMDC material. Step 6-3: Introduce O2 again at a gas flow rate of 100 sccm, a power of 100 W, a high valve setting of 100, and an etching time of 360 s. Under these conditions, remove the remaining SU8 photoresist to form the final patterned SU8 thin film / TMDC / substrate structure.

10. The method for patterning TMDC materials based on soft nanoimprinting according to claim 9, characterized in that: In step 6-2, when the TMDC material is completely etched through, the etching time in seconds is 5 seconds longer than the thickness value; when the TMDC material is not completely etched through, the etching time in seconds is equal to or less than the thickness value. Under these conditions, the exposed TMDC is further etched, and the etching depth is controlled by the etching time.

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