Method for fabricating suspended array device based on sacrificial layer and application thereof

Abstract

The application discloses a suspended array device preparation method based on a sacrifice layer and application thereof, and the method comprises the following steps: etching a channel, filling the channel with a sacrifice layer, polishing a sample surface, transferring a two-dimensional material, etching the two-dimensional material, evaporating source and drain electrodes, and removing the sacrifice layer. The application is applied to the field of micro-nano systems, in which an inorganic compound is evaporated as a temporary support in the suspended two-dimensional material device preparation process, so that the collapse and rupture of the two-dimensional material in the transfer process are overcome, a high-temperature gas reaction is used to remove the sacrifice layer, side etching and pollution caused by the commonly used wet etching are avoided, the surface tension caused by the contact between the two-dimensional material and the solution is avoided, a feasible scheme is provided for preparing a large-scale suspended two-dimensional material device which is stable in suspension, clean in surface and high in yield, and the large-scale suspended two-dimensional material array device prepared by the method can be used in large-area two-dimensional material light-emitting devices, nanoelectromechanical resonators, resonant sensors and other micro-nano systems.

Description

Technical Field

[0001] This invention relates to the field of micro-nano systems technology, specifically a method for fabricating large-scale suspended two-dimensional material array devices based on an inorganic compound sacrificial layer filling process and its application. Background Technology

[0002] Two-dimensional materials with suspended structures possess excellent physical and chemical properties. Taking graphene, the earliest discovered graphene, as an example, the suspended structure effectively avoids carrier scattering and phonon leakage caused by the substrate, allowing graphene's excellent mechanical, electrical, and thermal properties to be exhibited. Research results show that suspended graphene has a considerably high carrier mobility (2 × 10⁻⁶). 5 cm 2 / (V·s)), elastic stiffness (340N / m) and thermal conductivity (5×10 3 Excellent properties such as W / mK are also present. Furthermore, with continuous exploration in the field of two-dimensional materials, more and more different types of two-dimensional materials have been discovered and prepared. Two-dimensional materials can generally be divided into four categories: graphene-like materials, transition metal chalcogenides, non-transition metal chalcogenides, and layered oxides. Two-dimensional materials share the common characteristics of ultra-high surface area ratio and ultra-high sensitivity; suspended two-dimensional nanomaterial devices are highly sensitive to a variety of physical parameters. In addition to the common characteristics of two-dimensional materials, different two-dimensional materials also exhibit their unique properties. Therefore, suspended two-dimensional nanomaterials and devices have very broad application prospects, such as electromechanical resonators and high-precision sensors in micro-nano electromechanical systems; high-performance biomembranes and DNA sequence detection in the biological field; and light emission at different wavelengths and high-response photodetectors in the optical field.

[0003] As suspended two-dimensional devices move towards applications, the fabrication and production of their large-scale arrays are crucial. However, large-area fabrication of suspended two-dimensional material array devices remains a challenge. The fabrication process for a single suspended device is typically divided into top-down and bottom-up methods. In the top-down process, a pre-fabricated substrate is first prepared through processes such as photolithography, etching, and metal evaporation. Finally, the two-dimensional material is covered onto the pre-fabricated substrate by methods such as peeling, transfer, or direct growth to achieve suspension. However, transferring large areas of two-dimensional material onto the pre-fabricated substrate easily leads to breakage, collapse, and slippage of the two-dimensional material, resulting in low yield and making it difficult to fabricate array suspended devices. The bottom-up suspended graphene fabrication scheme first places the two-dimensional material on a substrate, then deposits electrodes and patterns the two-dimensional material, and finally uses methods such as etching to remove part of the substrate material beneath the two-dimensional material, achieving partial suspension of the two-dimensional material. Currently, the fabrication of large-scale suspended two-dimensional material devices typically employs a bottom-up approach. However, the commonly used wet etching method based on SiO2 substrates is prone to lateral etching and inevitably causes problems such as contamination, damage, curling, and wrinkling of the two-dimensional materials, severely affecting the performance of both the materials and the devices. Therefore, in the fabrication of large-scale suspended two-dimensional material array devices, how to balance fabrication efficiency and device quality, and optimize the fabrication process and technology to achieve stable suspension, clean surfaces, and high yield in large-scale suspended two-dimensional material array device fabrication, is a key technical challenge for advancing the application of suspended two-dimensional materials. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a method for fabricating large-scale suspended two-dimensional material array devices based on a sacrificial layer filling process and its application. The sacrificial layer is prepared by vapor deposition of inorganic compounds. By filling the channels with the sacrificial layer, the problems of side etching, contamination, breakage, curling, wrinkling, and low yield caused by traditional wet etching are overcome, thus achieving large-scale production of suspended two-dimensional material arrays with clean surfaces, high yield, and good process compatibility.

[0005] To achieve the above objectives, the present invention provides a method for fabricating a large-scale suspended two-dimensional material array device, comprising the following steps:

[0006] Step 1: Etch a channel array on the upper surface of the sample and deposit an inorganic compound as a sacrificial layer on the upper surface of the sample, so that the sacrificial layer fills all the channel arrays;

[0007] Step 2: Polish the upper surface of the sample, remove the sacrificial layer outside the channel array on the upper surface of the sample, and make the surface of the sacrificial layer inside the channel array flush with the outer surface of the trench array.

[0008] Step 3: Transfer a large area of ​​two-dimensional material onto the upper surface of the sample and cover all the channel arrays;

[0009] Step 4: Spin-coat photoresist on a large area of ​​two-dimensional material, expose and develop the two-dimensional material strip array pattern spanning the channel, and then etch the two-dimensional material outside the two-dimensional material strip array pattern to form two-dimensional material strips spanning the channel.

[0010] Step 5: Spin-coat photoresist on the upper surface of the sample, expose and develop the source and drain electrode array pattern, then vapor-deposit metal material on the upper surface of the sample, and form the source and drain electrode array through a stripping process.

[0011] Step 6: Use high-temperature gas reaction to remove the sacrificial layer in the channel array, thus forming a suspended two-dimensional material array device.

[0012] In one embodiment, step 1, the process of etching to form a channel array on the upper surface of the sample, is as follows:

[0013] Photoresist is spin-coated onto the upper surface of the sample, and the developed channel array pattern is exposed.

[0014] The upper surface of the sample is etched using inductively coupled plasma to form a channel array.

[0015] In one embodiment, the etching depth of the channel array is 0.1 μm to 1 μm, and the width of the channels in the channel array is 1 μm to 10 μm.

[0016] In one embodiment, in step 2, the polishing depth of the upper surface of the sample is greater than or equal to the thickness of the sacrificial layer on the upper surface of the sample, and the roughness of the upper surface of the sample after polishing does not exceed 2nm.

[0017] In one embodiment, in step 4, the two-dimensional material strips are respectively placed on both sides of the channel, and the width of the two-dimensional material strips does not exceed the length of the channel.

[0018] In one embodiment, in step 5, each group of source and drain electrodes in the source and drain electrode array contacts both ends of the two-dimensional material strip, and the thickness of each group of source and drain electrodes in the source and drain electrode array is 50nm to 100nm.

[0019] To achieve the above objectives, the present invention also provides an application of the above-described method for fabricating large-scale suspended two-dimensional material array devices, wherein the above-described method for fabricating large-scale suspended two-dimensional material array devices is used to fabricate large-scale suspended two-dimensional material array devices.

[0020] The large-scale suspended two-dimensional material array device consists of, from bottom to top, a bottom gate, an insulating layer, and two-dimensional materials and source / drain electrodes arranged in an array, wherein the insulating layer has channels arranged in an array.

[0021] In one embodiment, the two-dimensional material is at least one layer of graphene, boron nitride, two-dimensional transition metal chalcogenide, or layered oxide.

[0022] In one embodiment, the insulating layer is SiO2.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] 1. This invention selects an inorganic compound sacrificial layer as a temporary support in the fabrication process of suspended two-dimensional material devices, which overcomes the collapse and cracking of two-dimensional materials during the transfer process. Moreover, the sacrificial layer is easy to remove by high-temperature gas reaction, avoiding the side etching and contamination problems caused by commonly used wet etching. This provides a feasible solution for the fabrication of large-scale suspended two-dimensional material devices with stable suspension, clean surface and high yield.

[0025] 2. The large-scale suspended two-dimensional material array device provided by the present invention can be used in micro-nano systems such as large-area two-dimensional material light-emitting devices, nano-electromechanical resonators, and resonant sensors. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the method for fabricating a large-scale suspended two-dimensional material array device in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the fabrication process of a large-scale suspended two-dimensional material array device in an embodiment of the present invention;

[0029] Figure 3 This is a top view of a single device structure made of suspended two-dimensional material in an embodiment of the present invention;

[0030] Figure 4 This is a top view of the structure of a large-scale suspended two-dimensional material array device in an embodiment of the present invention.

[0031] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention 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 the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0034] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0035] like Figure 1 , Figure 2 The present embodiment discloses a method for fabricating a large-scale suspended two-dimensional material array device, which mainly includes the following steps 1 to 6.

[0036] Step 1 involves etching a channel array onto the upper surface of the sample and then covering the upper surface of the sample with a sacrificial layer 5, ensuring that the sacrificial layer 5 fills all the channel arrays. The specific implementation process is as follows:

[0037] First, a SiO2 / Si sample with a bottom gate 1 and an insulating layer 2 is selected, and photoresist 3 is spin-coated on the upper surface of the insulating layer 2 of the SiO2 / Si sample.

[0038] Then, after the channel array pattern is exposed and developed on the photoresist 3 on the upper surface of the SiO2 / Si sample insulating layer 2 by ultraviolet mask exposure, the channel array is formed by etching on the upper surface of the SiO2 / Si sample insulating layer 2 by inductively coupled plasma. The etching depth of the channel array is 0.1μm to 1μm, and the width of the channel 4 in the channel array is 1μm to 10μm.

[0039] Finally, a sacrificial layer 5 is placed on the upper surface of the insulating layer 2 with the channel array, and the sacrificial layer 5 fills all the channel arrays.

[0040] Step 2 involves polishing the upper surface of the sample, removing the sacrificial layer 5 outside the channel array on the upper surface of the sample, and making the surface of the sacrificial layer 5 within the channel array flush with the outer surface of the trench array. The specific implementation process is as follows:

[0041] Chemical mechanical polishing is used to remove the sacrificial layer 5 outside the trench 4 area on the upper surface of the insulating layer 2, and to make the surface of the sacrificial layer 5 inside the trench 4 flush with the outer surface of the trench. The polishing depth is greater than or equal to the thickness of the sacrificial layer 5 on the upper surface of the insulating layer 2. The upper surface of the insulating layer 2 should be smooth after polishing. Usually, the roughness of the upper surface of the insulating layer 2 after polishing does not exceed 2nm.

[0042] Step 3: Transfer the large-area two-dimensional material 6 to the upper surface of the sample, covering all the channel arrays. Specifically: Use methods such as transferring the large-area two-dimensional material 6 with a protective material to transfer it to the upper surface of the sample, covering all the channel arrays. The specific implementation process is as follows:

[0043] Large-area chemical vapor deposition (CVD) graphene from a copper substrate is transferred onto a sample using a transfer medium with a surface energy gradient distribution, such as polydimethylsiloxane (PDMS) / PMMA / borneol. PDMS serves as a support layer, enabling dry bonding of graphene to the target substrate and reducing interfacial water and oxygen doping. The easily volatile borneol acts as a small-molecule buffer layer, effectively preventing direct contact and residue contamination of the graphene by the upper PMMA polymer film, resulting in a clean graphene surface. The rigidity of the high-molecular-weight PMMA layer ensures that the graphene retains its ultra-flat properties after transfer.

[0044] Step 4: Spin-coat photoresist 3 onto a large area of ​​two-dimensional material 6, expose and develop the two-dimensional material strip array pattern spanning the channel 4 using ultraviolet mask exposure, then etch the two-dimensional material 6 outside the two-dimensional material strip array pattern to form two-dimensional material strips spanning the channel 4. The two-dimensional material strips are respectively placed on both sides of the channel 4, and the width of the two-dimensional material strips does not exceed the length of the channel 4.

[0045] Step 5: Spin-coat photoresist 3 onto the upper surface of the sample insulating layer 2 and the two-dimensional material strip. After exposing and developing the source and drain electrode array pattern by ultraviolet mask exposure, deposit a metal material with a thickness of 50nm to 100nm on the upper surface of the sample by metal evaporation technology. Then, form the source and drain electrode array by a stripping process, so that each group of source and drain electrodes 7 in the source and drain electrode array contacts the two ends of the two-dimensional material strip.

[0046] Step 6: The sacrificial layer 5 in the channel array is removed by high-temperature decomposition or gas reaction, thus forming a suspended two-dimensional material array device.

[0047] In this embodiment, the sacrificial layer 5 can be an inorganic compound, organic adhesive, or other material, but cannot be a conductive material. When removing the sacrificial layer 5 in the channel array by high-temperature decomposition or gas reaction in step 6, the process of removing the sacrificial layer 5 must not damage the two-dimensional material, metal electrode, or substrate.

[0048] A top view of the large-scale suspended two-dimensional material array device prepared by the above method is shown below. Figure 3 As shown, the top view of the array device is as follows Figure 4 As shown. In this embodiment, the large-scale suspended two-dimensional material array device consists of a bottom gate 1, an insulating layer 2, and arrayed two-dimensional materials 6 and source / drain electrodes 7, from bottom to top. The insulating layer 2 has arrayed channels 4. The bottom gate 1 is a highly doped silicon substrate, the insulating layer 2 is SiO2, and the two-dimensional material is graphene, boron nitride, two-dimensional transition metal chalcogenide, or layered oxide. The two-dimensional material can be a single layer, a few layers, or multiple layers.

[0049] The fabrication method of the large-scale suspended two-dimensional material array device in this embodiment will be further explained below with specific examples.

[0050] A method for fabricating large-scale suspended two-dimensional material array devices based on a sacrificial layer filling process includes the following steps:

[0051] Step 1: Spin-coat photoresist AZ5214 onto the surface of a highly doped silicon wafer with a 300nm insulating layer. After exposure and development of the channel array pattern and alignment marks using ultraviolet lithography, etch the silicon oxide layer using inductively coupled plasma, and remove the remaining photoresist with acetone to form the channel array and alignment marks. The channel width is approximately 2μm to 5μm, and the channel depth is 0.1μm to 1μm. After etching the channel array, deposit a vanadium dioxide layer with a thickness of approximately 300nm as a sacrificial layer on the sample surface using electron beam evaporation.

[0052] Step 2: Use chemical mechanical polishing to polish the sample surface to a depth of about 300 nm to make the vanadium dioxide surface inside the trench flush with the silicon oxide surface outside the trench.

[0053] Step 3: The monolayer graphene generated by large-area chemical vapor deposition is transferred to the sample surface formed in Step 2 by wet transfer and covers all channel arrays.

[0054] Step 4: Spin-coat the sample surface formed in step 3 with photoresist AZ5241, and use ultraviolet lithography to expose the graphene development strip array pattern. The width of the graphene strips is about 2μm-5μm. Then, etch the graphene in other areas outside the graphene development strips with oxygen plasma, and remove the remaining photoresist with acetone to form a graphene strip array spanning the channel.

[0055] Step 5: Spin-coat the sample surface formed in step 4 with photoresist AZ5214, and use ultraviolet lithography to expose and develop the source and drain electrode array pattern so that the source and drain electrodes are pressed onto both ends of the graphene strip respectively; then use electron beam evaporation to deposit 5nm chromium and 50nm gold on the sample surface in sequence, and use acetone to remove the remaining photoresist and metal through a stripping process to form the source and drain electrode array.

[0056] Step 6: Place the ammonium chloride material and the sample at the upstream and downstream ends of a vacuum tube furnace, respectively. Pour argon gas at a flow rate of 50-100 sccm into the furnace as a carrier gas and provide protection. The upstream ammonium chloride decomposes at 300-350℃, releasing hydrogen chloride gas. This gas reacts with the vanadium oxide layer on the sample surface at 350-400℃ in the downstream end, generating gaseous products. This removes the vanadium oxide in the channel, releasing the suspended graphene in the channel and forming a suspended two-dimensional material array device.

[0057] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for fabricating a suspended array device based on a sacrificial layer, characterized in that, Includes the following steps: Step 1: Etch a channel array on the upper surface of the sample and deposit an inorganic compound as a sacrificial layer on the upper surface of the sample, so that the sacrificial layer fills all the channel arrays, wherein the sacrificial layer is vanadium dioxide; Step 2: Polish the upper surface of the sample, remove the sacrificial layer outside the channel array on the upper surface of the sample, and make the surface of the sacrificial layer inside the channel array flush with the outer surface of the trench array. Step 3: Transfer a large area of ​​two-dimensional material onto the upper surface of the sample and cover all the channel arrays; Step 4: Spin-coat photoresist on a large area of ​​two-dimensional material, expose and develop the two-dimensional material strip array pattern spanning the channel, and then etch the two-dimensional material outside the two-dimensional material strip array pattern to form two-dimensional material strips spanning the channel. Step 5: Spin-coat photoresist on the upper surface of the sample, expose and develop the source and drain electrode array pattern, then vapor-deposit metal material on the upper surface of the sample, and form the source and drain electrode array through a stripping process. Step 6: Use high-temperature gas reaction to remove the sacrificial layer in the channel array, thus forming a suspended two-dimensional material array device.

2. The method for fabricating a suspended array device based on a sacrificial layer according to claim 1, characterized in that, In step 1, the process of etching a channel array on the upper surface of the sample is as follows: Photoresist is spin-coated onto the upper surface of the sample, and the developed channel array pattern is exposed. The upper surface of the sample is etched using inductively coupled plasma to form a channel array.

3. The method for fabricating a suspended array device based on a sacrificial layer according to claim 2, characterized in that, The etching depth of the channel array is 0.1 μm to 1 μm, and the width of the channels in the channel array is 1 μm to 10 μm.

4. The method for fabricating a suspended array device based on a sacrificial layer according to claim 1, 2, or 3, characterized in that, In step 2, the polishing depth of the sample surface is greater than or equal to the thickness of the sacrificial layer on the sample surface, and the roughness of the sample surface after polishing does not exceed 2nm.

5. The method for fabricating a suspended array device based on a sacrificial layer according to claim 1, 2, or 3, characterized in that, In step 4, the two-dimensional material strips are placed on both sides of the channel, and the width of the two-dimensional material strips does not exceed the length of the channel.

6. The method for fabricating a suspended array device based on a sacrificial layer according to claim 1, 2, or 3, characterized in that, In step 5, each group of source and drain electrodes in the source and drain electrode array contacts both ends of the two-dimensional material strip, and the thickness of each group of source and drain electrodes in the source and drain electrode array is 50nm~100nm.

7. The application of the method for fabricating a suspended array device based on a sacrificial layer according to any one of claims 1 to 6, characterized in that, Large-scale suspended two-dimensional material array devices are fabricated using the suspended array device fabrication method according to any one of claims 1 to 6; The large-scale suspended two-dimensional material array device consists of, from bottom to top, a bottom gate, an insulating layer, and two-dimensional materials and source / drain electrodes arranged in an array, wherein the insulating layer has channels arranged in an array.

8. The application of the method for fabricating a suspended array device based on a sacrificial layer according to claim 7, characterized in that, The two-dimensional material is at least one layer of graphene, boron nitride, two-dimensional transition metal chalcogenide, or layered oxide.

9. The application of the method for fabricating a suspended array device based on a sacrificial layer according to claim 7 or 8, characterized in that, The insulating layer is SiO2.

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