Nanowire fabrication method, gas sensor fabrication method and gas sensor

Abstract

This disclosure provides a method for fabricating nanowires, a method for fabricating a gas sensor, and a gas sensor. By employing block copolymer self-assembly technology, nanowires for high-performance nanowire gas sensors can be fabricated in large quantities at low cost. The process is simple and highly reproducible. The method includes: depositing a hard mask on a substrate with a material layer for fabricating nanowires on its surface; coating the hard mask with a block copolymer and allowing it to self-assemble; performing a first etching on the self-assembled block copolymer to form a random line pattern, and transferring the random line pattern to the hard mask; removing the block copolymer and performing a second etching using the hard mask as a template to transfer the pattern of the hard mask to the material layer of the substrate; and removing the hard mask, controlling the etching conditions of the second etching to create a bilayer structure in the etched material layer, with nanowires on top and a bottom layer thick enough to interconnect the nanowires.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a method for preparing nanowires, a method for preparing a gas sensor, and a gas sensor. Background Technology

[0002] A gas sensor is a device that converts parameters such as gas type and concentration into electrical signals. It can quickly and efficiently identify specific gases and provide timely monitoring and feedback on harmful waste gases generated in human industrial activities and social production, thereby regulating human production activities to ensure environmental safety.

[0003] With the increasing severity of air pollution, higher demands are being placed on gas detection technology, leading to the development of novel sensors based on nanomaterials. Among these, gas sensors based on silicon nanowires offer advantages such as higher sensitivity, lower operating temperature, and smaller device size. Furthermore, silicon nanowires have relatively standardized processing techniques and mature fabrication processes, giving them a significant advantage in the field of gas sensing.

[0004] Currently, the main methods for fabricating silicon nanowires include direct photolithography, sidewall transfer photolithography, metal-assisted catalytic etching, metal-catalytic assisted chemical vapor deposition (MCCVD), and guided self-assembly photolithography. Among these, direct photolithography is compatible with existing silicon-based device manufacturing processes and can mass-produce silicon nanowires smaller than 10 nm; however, the required photolithography equipment is very expensive, resulting in high costs. While sidewall transfer photolithography does not require high precision, it involves many photolithography, deposition, and etching steps, increasing process complexity and hindering cost reduction. Metal-assisted catalytic etching is beneficial for heterogeneous composites of silicon with other materials to improve the sensitivity of gas sensors, but its repeatability is low. Although metal-catalytic assisted chemical vapor deposition can generate high-quality, length-controllable single-crystal silicon nanowires, its growth process is slow, time-consuming, and prone to metal contamination. Guided self-assembly photolithography requires coordination with other photolithography techniques to guide the self-assembly process of block copolymers, thus introducing the inherent limitations of other photolithography techniques, such as the low efficiency and high cost of electron beam lithography.

[0005] Therefore, although silicon nanowire fabrication technology is relatively mature, problems such as high cost, low production efficiency, high process complexity and poor repeatability limit the large-scale application of silicon nanowire-based gas sensors. Summary of the Invention

[0006] The technical problem to be solved by the present invention

[0007] In view of the above, the purpose of this invention is to provide a simple and low-cost method for preparing nanowires, a method for preparing gas sensors, and a high-performance gas sensor.

[0008] Technical means for solving technical problems

[0009] To address the aforementioned technical problems, according to some exemplary embodiments of this disclosure, a method for preparing nanowires is provided, comprising:

[0010] The step of depositing a hard mask on a substrate having a material layer on its surface for fabricating the nanowires;

[0011] The step of coating the block copolymer onto the hard mask and allowing it to self-assemble;

[0012] The steps include: first etching the self-assembled block copolymer to form a random line pattern, and transferring the pattern of the random line pattern to the hard mask;

[0013] The steps of removing the block copolymer, performing a second etching using the hard mask as a template, and transferring the pattern of the hard mask to the material layer of the substrate; and

[0014] The step of removing the hard mask,

[0015] The etching conditions of the second etching are controlled so that the etched material layer has a bilayer structure with nanowires on the top and a bottom layer of thickness capable of interconnecting the nanowires.

[0016] In some embodiments, the etching conditions include etching time.

[0017] By controlling the etching time of the second etching, the etching depth of the material layer is made smaller than the thickness of the material layer.

[0018] In some embodiments, the substrate has a semiconductor-on-insulator structure, including a semiconductor substrate, a buried oxide layer as an insulating layer, and a semiconductor layer as the material layer.

[0019] The semiconductor substrate includes any one of the following semiconductor materials: silicon, germanium, germanium-silicon, gallium nitride, and indium gallium arsenide.

[0020] The buried oxide layer comprises any one of the insulating materials selected from silicon dioxide, aluminum oxide, and hafnium oxide.

[0021] The material layer includes any one of the following semiconductor materials: silicon, germanium, germanium silicon, gallium nitride, and indium gallium arsenide.

[0022] In some embodiments, the hard mask used includes one or more materials selected from silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.

[0023] In some embodiments, the block copolymer has an AB, ABA, or ABC structure, where A, B, and C represent different block components, and the mass content of one block component in the block copolymer is 30% to 60%.

[0024] In some embodiments, the block copolymer is PS-b-PMMA, wherein PS represents the block component of polystyrene and PMMA represents the block component of polymethyl methacrylate.

[0025] In some embodiments, the first etching is a dry etching using oxygen, argon plasma etching or fluorine-based plasma etching, or a wet etching using acetic acid, hydrochloric acid, sulfuric acid or hydrofluoric acid.

[0026] In some embodiments, the second etching is dry etching using halogen gas or wet etching using strong acid or strong alkali solution.

[0027] According to some exemplary embodiments of this disclosure, a method for preparing a gas sensor is also provided, comprising:

[0028] The steps of preparing nanowires using any of the above-described nanowire preparation methods, wherein the material layer is a sensing layer with gas sensing function; and

[0029] The steps include photolithography of the bilayer structure of the nanowires and deposition of source / drain metals.

[0030] In some embodiments, the source / drain metals used include one or more of the following materials: titanium, nickel, gold, silver, copper, cobalt, tungsten, thallium, tantalum, platinum, aluminum, palladium, and zinc.

[0031] According to some exemplary embodiments of this disclosure, a gas sensor is also provided, comprising:

[0032] Substrate;

[0033] A gas-sensing material layer disposed on the substrate; and

[0034] Source / drain metal disposed in a designated area of ​​the material layer

[0035] The material layer is etched to form a two-layer structure, with the upper layer being nanowires and the lower layer retaining the thickness to interconnect the nanowires.

[0036] Invention Effects

[0037] This invention employs block copolymer self-assembly technology as a nanowire manufacturing process for high-performance nanowire gas sensors. This allows for the low-cost, high-volume fabrication of nanowires, with a simple and highly reproducible process. Furthermore, by using unguided block copolymer self-assembled nanowires as templates and controlling etching parameters, a large number of long-range, disordered, random nanowires can be interconnected. This not only avoids the inherent limitations of introducing other photolithography techniques to achieve a guiding effect but also enables the formation of stable and effective devices using random nanowire templates, which are not widely used. This significantly expands the application potential of self-assembly technology in semiconductor device manufacturing. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the embodiments of the present disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a flowchart of the preparation method of the nanowire gas sensor according to Embodiment 1 of the present invention.

[0040] Figure 2 This is a process flow diagram of the nanowire gas sensor according to Embodiment 1 of the present invention.

[0041] Figure 3 This is a SEM planar view of the nanowire gas sensor according to Embodiment 1 of the present invention.

[0042] Figure 4 These are the measured device performance curves of the nanowire gas sensor according to Embodiment 1 of the present invention.

[0043] Figure 5 This is a graph showing the sensitivity of the nanowire gas sensor of Embodiment 1 of the present invention at different ammonia concentrations.

[0044] Figure 6 This is a flowchart of the preparation method of the nanowire gas sensor according to Embodiment 2 of the present invention.

[0045] Figure 7 This is a process flow diagram of the nanowire gas sensor according to Embodiment 2 of the present invention. Detailed Implementation

[0046] The following describes specific embodiments of this disclosure. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this disclosure, changes in design, manufacturing, or production based on the technical content disclosed in this disclosure are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0047] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar words used in this patent application description and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms “an” or “a” and similar words do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar words mean that the element or object preceding “comprising” or “including” encompasses the element or object listed following “comprising” or “including” and its equivalents, and do not exclude other elements or objects. The terms “connected,” “coupled,” or “linked” and similar words are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0048] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions. Similarly, unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0049] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0050] The following describes in detail, with reference to the accompanying drawings, the nanowire preparation method, the nanowire gas sensor preparation method, and the nanowire gas sensor provided according to embodiments of the present disclosure.

[0051] <Implementation Method 1>

[0052] Figure 1 This is a flowchart of the preparation method of the nanowire gas sensor according to Embodiment 1 of the present invention. Figure 2 This is a process flow diagram of the nanowire gas sensor according to Embodiment 1 of the present invention. In this Embodiment 1, a high-performance silicon nanowire gas sensor is fabricated on a silicon-on-insulator (SOI) substrate using block copolymer self-assembly technology as an example.

[0053] First, in step S101, a substrate is prepared and cleaned to obtain a clean surface. The substrate in this embodiment 1 is an SOI substrate with short-channel effect and low parasitic capacitance, such as... Figure 2 As shown in (a), the SOI substrate 20 has a stacked structure including a substrate 201, a buried oxide layer 202 as an insulating layer, and a silicon layer 203 as an upper channel. The substrate 201 can be a variety of semiconductors such as silicon, germanium, germanium-silicon, gallium nitride, or indium gallium arsenide, and the buried oxide layer 202 can be an insulating material such as silicon dioxide, aluminum oxide, or hafnium oxide. Furthermore, the cleaning method for the substrate 20 is not particularly limited; for example, the RCA standard cleaning method can be used. In addition, depending on the specific application scenario of the gas sensor, ion implantation can be performed on the substrate 20 to obtain a P-type or N-type SOI substrate.

[0054] Then, in step S102, a hard mask 21 is deposited on the substrate 20, as follows: Figure 2 As shown in (b). In this embodiment 1, the material of the hard mask 21 is silicon dioxide, but it is not limited to this, and it can also be one or more of the hard mask materials such as silicon nitride, aluminum oxide, and hafnium oxide. In addition, the process for depositing the hard mask 21 can be chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0055] Next, in step S103, the block copolymer 22 is coated onto the hard mask 21, and the self-assembly process is completed. In this embodiment 1, the self-assembly of PS-b-PMMA block copolymer material by spin coating is described as an example. The block copolymer 22 is a diblock copolymer with an AB structure, where A represents the block component of polystyrene (PS), B represents the block component of polymethyl methacrylate (PMMA), and the mass content of block component A is 30% to 60%. The structure of the block copolymer 22 is not limited to this; it can also be an ABA triblock copolymer, such as P2VP-b-PS-b-P2VP, where P2VP represents poly(2-vinylpyridine) and PS represents polystyrene. The block copolymer 22 can also be an ABC triblock copolymer or a copolymer of more blocks, such as PI-b-PS-b-P2VP, where PI represents polypyrrolidine, PS represents polystyrene, and P2VP represents poly(2-vinylpyridine). In addition, the block component A may also have a mass content of 30% to 60%, not limited to the case where the mass content of block component B or C is 30% to 60%.

[0056] The self-assembly process of the block copolymer in step S103 can be accomplished by vacuum heating annealing, solvent vapor annealing, or ultraviolet irradiation. When using vacuum heating annealing, the annealing temperature is 100℃~250℃, and the annealing time is 1min~24h. When using solvent vapor annealing, the annealing temperature is room temperature, and the annealing time is 1min~48h. Alternatively, ultraviolet irradiation can also cause microphase separation in the block copolymer, thereby completing the self-assembly.

[0057] In this embodiment 1, the PS-b-PMMA block copolymer 22 coated on the hard mask 21 completes self-assembly to form Figure 2 (c) shows PS phase 221 and PMMA phase 222.

[0058] Then, in step S104, the self-assembled block copolymer 22 is etched to remove the PMMA phase 222, and the PS phase 221 forms an initial random line pattern. Next, using the PS phase 221 as a template, further etching is performed to transfer the pattern to the hard mask 21, as shown below. Figure 2 As shown in (d). The etching used in step S104 can be dry etching or wet etching. Dry etching generally uses oxygen, argon plasma etching or fluorine-based plasma etching, while wet etching uses acetic acid, hydrochloric acid, sulfuric acid or hydrofluoric acid.

[0059] In step S105, the remaining PS phase 221 is removed by dry etching or wet etching, resulting in a layer on the substrate 20. Figure 2 (e) shows the patterned hard mask 21.

[0060] Then, in step S106, with Figure 2 (e) The hard mask 21 shown is a template, and its pattern is transferred to the silicon layer 203 on the upper surface of the SOI substrate 20 through etching. In this step, etching parameters such as etching time are controlled to prevent the silicon layer 203 from being etched through. Figure 2 As shown in (f), the silicon layer 203 was not completely etched, but a thin silicon layer of 3-5 nm was retained at its bottom. The etching used in this step can be either dry etching or wet etching. Dry etching can be performed using halogen gases, while wet etching can be performed using strong acid or strong alkali solutions.

[0061] In step S107, the hard mask 21 is removed to obtain a bilayer structure 23 with silicon nanowires on top and a thin silicon layer on the bottom, as shown below. Figure 2 As shown in (g), the upper silicon nanowires are a large number of long-range disordered random nanowires formed by the self-assembly properties of the block copolymer 22 through steps S104 to S106, while the lower thin silicon layer can ensure the interconnection between these nanowires.

[0062] Then, in step S108, for Figure 2 (g) The bilayer structure 23 shown is photolithographically etched to define the source and drain regions of the device. For example, source and drain metals 24 are deposited at the left and right ends as shown in the figure. After annealing, ohmic contacts are formed, resulting in a silicon nanowire gas sensor with a large number of random nanolines. The source and drain metals 24 here can be one or more of titanium, nickel, gold, silver, copper, cobalt, tungsten, thallium, tantalum, platinum, aluminum, palladium, and zinc.

[0063] Figure 3 This is a SEM planar image of the silicon nanowire gas sensor according to Embodiment 1 of the present invention. The linewidth of the silicon nanowire gas sensor prepared by steps S101 to S108 is 7 nm.

[0064] Figure 4 These are the measured device performance curves of the nanowire gas sensor according to Embodiment 1 of the present invention. In the figure, the vertical axis I... D The horizontal axis V represents the magnitude of the current flowing between the source and drain electrodes of the sensor. B This indicates the back grid voltage of the sensor. Figure 4 The diagram shows the source-drain current I under a fixed source-drain voltage (in this embodiment 1, the source-drain voltage is fixed at 1V). D With back gate voltage V B The changes. From Figure 4 It can be seen that the source-leakage current I of the nanowire gas sensor in Embodiment 1 of the present invention in air is... D With back gate voltage V BThe current gradually increases as it grows (as shown by the black curve in the figure), exhibiting clear characteristics of an N-channel device. When the sensor is exposed to nitrogen (N2), its characteristics are basically the same as in air, and it shows a significant current increase at higher back-gate voltages (as shown by the red curve in the figure). This is because when the sensor channel is exposed to air, oxidizing gases such as oxygen and carbon dioxide in the air adsorb onto the surface of the channel, taking electrons from the channel and keeping the channel current at a low level. However, nitrogen, as an inert gas, does not interact with electrons on the channel surface, thus reducing the amount of oxidizing gas on the sensor surface and causing the current to rise.

[0065] Figure 4 The blue and blue-green curves in the image represent the source and leakage current curves of the sensor under different concentrations of ammonia (NH3), respectively. Ammonia, as a reducing gas, injects electrons into the sensor's channel, reducing the channel resistance and increasing the current. Furthermore, the current increases with increasing ammonia concentration.

[0066] Figure 5 This is a graph showing the sensitivity of the silicon nanowire gas sensor according to Embodiment 1 of the present invention at different ammonia concentrations. Figure 5 The formula for calculating sensitivity is:

[0067]

[0068] Among them, I D This represents the source and leakage current value of the sensor in the target gas, where the target gas is ammonia (NH3).

[0069] I D0 This indicates the current value of the sensor in the reference gas, where the reference gas is nitrogen (N2).

[0070] according to Figure 4 The source and drain current values ​​shown in the different gases can be obtained Figure 5 The sensitivity shown indicates that the silicon nanowire gas sensor has extremely high sensitivity to ammonia (NH3). For example, when operating at room temperature, the sensitivity is 251.3% for 1.1 ppm ammonia and 8717.5% for 108 ppm ammonia.

[0071] Therefore, according to the method for fabricating a silicon nanowire gas sensor according to Embodiment 1, a large number of random nanowire patterns are obtained rapidly and at low cost by utilizing the self-assembly of block copolymers. Subsequently, the pattern is transferred to the substrate by precisely controlling the etching transfer process while retaining a thin silicon layer at the bottom, forming a bilayer structure with lines on the upper layer and thin silicon on the lower layer. The thin silicon layer on the lower layer is used to assist the interconnection of the long-range disordered lines on the upper layer, thereby constructing a stable and reliable device and realizing a highly sensitive gas sensing function.

[0072] <Implementation Method 2>

[0073] In the above embodiment 1, a silicon-on-insulator (SOI) substrate was used. The high-performance gas sensor was also fabricated based on silicon nanolines fabricated on the SOI substrate using self-assembly technology. The sensing function was completed by precisely controlling the etching to retain the thin silicon layer at the bottom and assisting the top lines to conduct electricity.

[0074] In the field of gas sensing, materials capable of sensing functions are not limited to silicon; they can also be metal oxide semiconductors, conductive polymers, and other composite materials with sensing capabilities. Therefore, in this second embodiment, a method for fabricating a nanowire gas sensor using other substrates will be described. In the following description, parts that differ from those in embodiment 1 will be described in detail, while parts that are the same or similar will be described briefly.

[0075] Figure 6 This is a flowchart of the preparation method of the nanowire gas sensor according to Embodiment 2 of the present invention. Figure 7 (a)~ Figure 7 (j) is a process flow diagram of the nanowire gas sensor of Embodiment 2 of the present invention.

[0076] First, in step S601, a substrate is prepared, for example... Figure 7 (a) shows the bulk silicon substrate 701. In addition to silicon, the substrate material can also be a variety of semiconductor materials such as germanium, germanium silicon, gallium nitride, or indium gallium arsenide.

[0077] Next, in step S602, an insulating layer 702 is grown on the bulk silicon substrate 701, as a substrate, such as... Figure 7 As shown in (b). The insulating layer 702 can be an insulating material such as silicon dioxide, aluminum oxide, and hafnium oxide.

[0078] In step S603, a semiconductor material for realizing the sensing function is deposited on the insulating layer 702, such as... Figure 7 As shown in (c), a sensing layer 703 is formed. As described above, the material of the sensing layer 703 is not limited to silicon, but can also be other composite materials with sensing functions, such as metal oxide semiconductors such as ZnO, SnO2, and WO3, conductive polymers such as polyaniline, polypyrrole, and polythiophene, and graphene-based composite materials.

[0079] After steps S601 to S603, a substrate comprising a substrate 701, an insulating layer 702, and a sensing layer 703, as described in Embodiment 2, is prepared. Then, a nanowire gas sensor of this embodiment is fabricated on this substrate, wherein the nanowires are formed from the material of the sensing layer 703. Specifically, steps S604 to S610 correspond to Embodiment 1. Figure 1 Steps S102 to S108 in the above. Below, in conjunction with... Figure 7 A brief explanation is provided.

[0080] First, such as Figure 7 As shown in (d), a hard mask 71, such as SiO2, is deposited on the upper surface of the sensing layer 703 of the substrate (step S604). Then, a PS-b-PMMA block copolymer 72, such as PS-b-PMMA, is coated onto the hard mask 71, and a self-assembly process is performed, as shown in (d). Figure 7 As shown in (e), after microphase separation, PS phase 721 and PMMA phase 722 are formed (step S605). Next, the PMMA phase 722 is removed by etching, forming an initial random line pattern composed of PS phase 721. This random line pattern is then used as a mask for further etching, transferring the pattern to hard mask 71, as shown in [example]. Figure 7 (f) is shown (step S606). Then, the PS phase 721 is removed to obtain... Figure 7 (g) The patterned hard mask 71 is shown (step S607). Using this hard mask 71 as a template, its pattern is transferred to the sensing layer 703 of the substrate by etching, as shown. Figure 7 As shown in (h), by controlling etching parameters such as etching time of sensing layer 703, the sensing layer 703 is prevented from being etched through, leaving a thin layer of a certain thickness at its bottom for interconnection of the upper line structure (step S608). Then, the hard mask 71 is removed to obtain a double-layer structure 73 formed by sensing layer 703 with nanowires on the upper layer and a thin layer on the lower layer, as shown in (h). Figure 7 (i) is shown in step S609. Here, the upper nanowires are a large number of long-range disordered random nanowires formed through steps S605 to S608 based on the self-assembly properties of the block copolymer 72, while the lower thin layer ensures the interconnection between these nanowires. Finally, in step S610, source and drain regions are defined at the left and right ends of the bilayer structure 73 and source and drain metals 74 are deposited to complete the fabrication of the gas sensor device.

[0081] According to the exemplary embodiments described above, a method for fabricating a nanowire gas sensor is provided, wherein the method for fabricating nanowires includes:

[0082] The step of depositing a hard mask on a substrate having a material layer on its surface for fabricating nanowires;

[0083] The step of coating a block copolymer onto a hard mask and allowing it to self-assemble;

[0084] The steps include: first etching the self-assembled block copolymer to form a random line pattern, and transferring the random line pattern to a hard mask;

[0085] The steps of removing the block copolymer and performing a second etching using a hard mask as a template to transfer the pattern of the hard mask to the material layer of the substrate; and,

[0086] The steps to remove the hard mask,

[0087] The etching conditions of the second etching are controlled so that the etched material layer has a bilayer structure with nanowires on top and a bottom layer of thickness capable of interconnecting the nanowires.

[0088] It also includes the steps of photolithography on the bilayer structure of the nanowires and deposition of source and drain metals.

[0089] Therefore, by using block copolymer self-assembly technology as the manufacturing process for nanowires in high-performance nanowire gas sensors, nanowires can be prepared in large quantities at low cost, with a simple process and high repeatability.

[0090] Meanwhile, by selecting unguided self-assembled lines of block copolymers as templates and controlling etching parameters, a large number of long-range disordered random nanowires can be interconnected. This not only avoids the inherent limitations of introducing other photolithography techniques to achieve the guiding effect, but also effectively utilizes random line templates, which are not widely used, to manufacture high-sensitivity and stable high-performance nanowire gas sensors, greatly expanding the application potential of guided self-assembly photolithography in semiconductor device manufacturing.

[0091] Moreover, in the gas sensor formed by the above method, the material layer with gas sensing function is etched to form a double-layer structure. The upper layer is a nanowire formed by the self-assembly technology of block copolymers, and the bottom layer retains the thickness to interconnect the nanowires. Thus, a large number of long-range disordered random nanowires can be interconnected. Compared with the straight lines formed by direct generation or photolithography and pattern transfer in the past, a longer line length can be achieved. Gas sensors with such nanowire structures can achieve a larger specific surface area when the length of the source and drain metals is the same, thereby obtaining a better sensing effect.

[0092] It should be understood that the above description is illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) can be used in combination with each other. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the various embodiments of this disclosure without departing from the scope of this disclosure. While the dimensions and types of materials described herein are used to define parameters of the various embodiments of this disclosure, the embodiments are not intended to be restrictive but are exemplary. Many other embodiments will become apparent to those skilled in the art upon reading the above description. Therefore, the scope of the various embodiments of this disclosure should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. A method for preparing nanowires, characterized in that, include: The step of depositing a hard mask on a substrate having a material layer on its surface for fabricating the nanowires; The step of coating the block copolymer onto the hard mask and allowing it to self-assemble; The steps include: first etching the self-assembled block copolymer to form a random line pattern, and transferring the pattern of the random line pattern to the hard mask; The steps include removing the block copolymer, performing a second etching using the hard mask as a template, and transferring the pattern of the hard mask to the material layer of the substrate; as well as The step of removing the hard mask, The etching conditions of the second etching are controlled so that the etched material layer has a bilayer structure with nanowires on the top and a bottom layer of thickness capable of interconnecting the nanowires.

2. The nanowire preparation method according to claim 1, characterized in that, The etching conditions include etching time. By controlling the etching time of the second etching, the etching depth of the material layer is made smaller than the thickness of the material layer.

3. The method for preparing nanowires as described in claim 1 or 2, characterized in that, The substrate has a semiconductor-on-insulator structure, including a semiconductor substrate, a buried oxide layer as an insulating layer, and a semiconductor layer as the material layer. The semiconductor substrate includes any one of the following semiconductor materials: silicon, germanium, germanium-silicon, gallium nitride, and indium gallium arsenide. The buried oxide layer comprises any one of the insulating materials selected from silicon dioxide, aluminum oxide, and hafnium oxide. The material layer includes any one of the following semiconductor materials: silicon, germanium, germanium silicon, gallium nitride, and indium gallium arsenide.

4. The method for preparing nanowires as described in claim 1 or 2, characterized in that, The hard mask used includes any one or more of the following materials: silicon oxide, silicon nitride, aluminum oxide, and hafnium oxide.

5. The method for preparing nanowires as described in claim 1 or 2, characterized in that, The block copolymer has an AB, ABA, or ABC structure, where A, B, and C represent different block components, and the mass content of one block component in the block copolymer is 30% to 60%.

6. The method for preparing nanowires as described in claim 5, characterized in that, The block copolymer is PS-b-PMMA, where PS represents the block component of polystyrene and PMMA represents the block component of polymethyl methacrylate.

7. The method for preparing nanowires as described in claim 1 or 2, characterized in that, The first etching is a dry etching method using oxygen, argon plasma etching or fluorine-based plasma etching, or a wet etching method using acetic acid, hydrochloric acid, sulfuric acid or hydrofluoric acid.

8. The method for preparing nanowires as described in claim 1 or 2, characterized in that, The second etching is dry etching using halogen gas or wet etching using strong acid or strong alkali solution.

9. A method for preparing a gas sensor, characterized in that, include: The step of preparing nanowires using the nanowire preparation method according to any one of claims 1 to 8, wherein the material layer is a sensing layer with gas sensing function; as well as The steps include photolithography of the bilayer structure of the nanowires and deposition of source / drain metals.

10. The method for preparing a gas sensor as described in claim 9, characterized in that, The source and drain metals used include one or more of the following materials: titanium, nickel, gold, silver, copper, cobalt, tungsten, thallium, tantalum, platinum, aluminum, palladium, and zinc.

11. A gas sensor, characterized in that, include: Substrate; A gas-sensing material layer disposed on the substrate; as well as Source / drain metal disposed in a designated area of ​​the material layer The material layer is etched to form a two-layer structure, with the upper layer being nanowires and the lower layer retaining the thickness to interconnect the nanowires.

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