Bridge structure air channel diode and preparation method thereof

Abstract

The application relates to the fields of semiconductor technology and micro-nano vacuum electron technology, in particular to a bridge structure air channel diode and a preparation method thereof. The diode comprises a substrate, a first metal layer, a second metal layer and an electrode structure arranged on the upper surface of the substrate; the electrode structure is located between the first metal layer and the second metal layer; the electrode structure comprises a lower electrode and a bridge upper electrode; the bridge upper electrode is made of a conductive material capable of being elastically deformed under an applied voltage, is coaxially sleeved outside the lower electrode, and has a gap with the lower electrode to form an air channel. The diode has the advantages of low threshold voltage, no insulation medium support, small electrode overlapping area, low inter-electrode capacitance, dynamically tunable air channel size and the like, and the preparation process is not dependent on high nano-processing equipment, and the preparation method of the vertical structure nano air channel diode can be batch-prepared.

Description

Technical Field

[0001] The present invention relates to the fields of semiconductor technology and micro-nano vacuum electronic technology, and in particular to a bridge-structured air channel diode and a preparation method thereof.

[0002] Micro-nano air channel devices (also known as micro-nano vacuum devices), particularly nanometer air channel devices with air channel dimensions smaller than the mean free path of electrons in air, combine the fast electron transit time and radiation resistance of vacuum devices with the small size, low power consumption, and easy integration of traditional solid-state electronic devices. Electrons can be transported ballistically through the air channel without scattering, achieving high-speed and high-frequency operation while reducing losses. They have a wide range of applications in switching, microwave rectification, and mixing circuits.

[0003] Nano air channel devices are divided into two types: horizontal structure and vertical structure. The preparation of air channels in horizontal structure devices usually uses processes such as FIB and IBE, which have high production costs, long process time, and are difficult to integrate on a large scale. There are also problems such as small device emission area, low current intensity, and easy damage. Vertical structure nano air channel devices add a dielectric layer between the upper and lower electrodes to play an insulating and supporting role, and selectively remove the dielectric material through a wet etching process to form a nano air channel. Compared with the horizontal structure, the vertical structure nano air channel device has more advantages in precision control and manufacturing cost. However, the following problems still exist:

[0004] 1. Due to the existence of the retained insulating dielectric layer, the utilization rate of the effective emission area of ​​the electrode is low and the parasitic capacitance of the device is large, making it difficult to effectively exert its advantages of high frequency and high speed; the film quality of the insulating dielectric layer affects the voltage and power tolerance of the device. When the insulating dielectric film is thin or the film quality is poor, soft breakdown is prone to occur.

[0005] 2. The depth of the nano-air channel is greatly affected by the etching process, resulting in relatively poor consistency of this type of device;

[0006] 3. The size of the nano-air channel is relatively fixed, which makes the tunable range of electrical properties small, and the tunable range of device electrical properties is small.

[0007] Therefore, designing a vertical structure nano air channel diode that does not require insulating dielectric support can not only increase the effective emission area of ​​the device and improve the emission current, but also reduce the inter-electrode capacitance to improve the high-frequency dynamic performance of the device, and ensure the consistency of device preparation and electrical performance, which has extremely important practical value. Summary of the Invention

[0008] In view of this, the present invention proposes a bridge-structured air channel diode and a preparation method thereof. The diode has the advantages of low threshold voltage, no insulating dielectric support, small electrode overlap area, low inter-electrode capacitance, and dynamically tunable air channel size. The preparation process does not rely on expensive nano-processing equipment and the preparation method of vertical structure nano air channel diodes can be mass-produced.

[0009] The technical solution of the present invention is:

[0010] A bridge-type air channel diode comprises a substrate and a first metal layer, a second metal layer and an electrode structure arranged on the upper surface of the substrate;

[0011] The electrode structure is located between the first metal layer and the second metal layer; it includes a lower electrode and a bridge-type upper electrode; the bridge-type upper electrode is made of a conductive material that can undergo elastic deformation under an external voltage, is coaxially sleeved outside the lower electrode, and leaves a gap between the lower electrode and the lower electrode to form an air channel.

[0012] Furthermore, the substrate material is an insulating material or a semiconductor material, preferably silicon.

[0013] Furthermore, the lower electrode material is a low-dimensional material or semiconductor material such as metal, metalloid, transparent conductive film, graphene, etc.; when light-assisted field emission enhancement is required, a transparent conductive material is preferred.

[0014] Furthermore, the lower electrode is processed using a semiconductor micro-nano process to obtain a lower electrode with a micro-nano structure having a field enhancement effect.

[0015] Furthermore, when the electrode is made of a transparent conductive material, light-assisted field emission enhancement can be achieved.

[0016] Furthermore, the first metal layer and the second metal layer are both made of conductive materials.

[0017] Furthermore, the lower electrode and the bridge-type upper electrode can both serve as electrodes for electron emission; when a negative bias is applied to the lower electrode and a positive bias is applied to the upper electrode, electrons are emitted from the lower electrode and collected by the bridge-type upper electrode; when a positive bias is applied to the lower electrode and a negative bias is applied to the bridge-type upper electrode, electrons are emitted from the bridge-type upper electrode and collected by the lower electrode.

[0018] Furthermore, the lower electrode is in a trapezoidal, comb-like or spherical shape, and the surface electric field strength of the lower electrode is enhanced by changing the shape of the lower electrode, thereby obtaining a larger current.

[0019] Furthermore, there are multiple lower electrodes, which are arranged in parallel, and each electrode does not contact each other. All electrodes are covered by the bridge-type upper electrode. A gap is left between each lower electrode and the bridge-type upper electrode to serve as an air channel, and all air channels are not connected to each other.

[0020] Furthermore, the size of the air channel is smaller than the mean free path of electron scattering in the air, which can ensure that electrons are ballistically transported in the air without scattering.

[0021] The method for preparing the bridge-type air channel diode comprises the following steps:

[0022] S1. Forming a lower electrode on the upper surface of the substrate using a semiconductor process, wherein the lower electrode is located in the middle of the upper surface;

[0023] S2, depositing a dielectric sacrificial layer on the upper surface of the structure obtained in S1, wherein the sacrificial layer covers the lower electrode;

[0024] S3, selectively removing part of the dielectric sacrificial layer by an overlay process, leaving only the sacrificial layer covering the lower electrode;

[0025] S4. Perform secondary photolithography on the upper surface of the structure obtained in S3 to form a bridge-type upper electrode and two metal conductive layers; the bridge-type upper electrode is coated on the remaining dielectric sacrificial layer, and the bridge-type upper electrode and the lower electrode together constitute an electrode structure, and the two metal conductive layers are located on both sides of the electrode structure, and the three metal conductive layers do not contact each other;

[0026] S5. Use a wet etching or dry etching process to completely remove the dielectric sacrificial layer between the lower electrode and the bridge upper electrode to form an air channel.

[0027] Furthermore, the dielectric sacrificial layer material is a metal, an insulator or a semiconductor that can be released by wet etching or dry etching.

[0028] Furthermore, the thickness of the dielectric sacrificial layer is greater than the thickness of the lower electrode.

[0029] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0030] 1. This invention completely eliminates the dielectric sacrificial layer. This allows the upper and lower electrodes to overlap and align vertically, resolving issues such as the difficulty in controlling electronic behavior and low electron collection efficiency seen in traditional vertical micro-nano air channel devices. Furthermore, it eliminates the impact of the dielectric sacrificial layer's film quality on the device's voltage and functional tolerance, ensuring consistent device performance.

[0031] 2. This invention enhances the electric field strength on the lower electrode surface by screening the work function of the electrode material and designing a rational lower electrode structure, thereby adjusting and optimizing the device threshold voltage and improving the electrode emission current. By applying an external bias to elastically deform the bridge structure, the air channel size can be dynamically tuned, further optimizing the device threshold voltage and enhancing the device's current emission characteristics.

[0032] Since the bridge-type upper electrode of the present invention is made of a conductive material capable of elastically deforming under an applied voltage, the elastic deformation under an applied voltage reduces the size of the air channel between the lower electrode and the bridge-type upper electrode, thereby enhancing the emission current.

[0033] 3. The present invention precisely controls the thickness of the sacrificial layer through semiconductor technology, achieving precise control of the air channel size at the nanoscale. By completely removing the sacrificial layer, the consistency of device performance is ensured, and it has practical potential for large-area wafer-level mass production.

[0034] 4. The nanometer air channel diode of the present invention significantly reduces the process requirements for the lower electrode and dielectric sacrificial layer during fabrication. It does not rely on expensive nanofabrication equipment, requiring only conventional UV lithography to achieve nanoscale air channels. It is applicable to a variety of substrates, including insulating substrates, inorganic semiconductors, and flexible organic semiconductors. It is also universally applicable to nanometer air channel devices with conductors, semiconductors, transparent conductive films, and graphene low-dimensional materials as electrode structures. Therefore, it is low-cost, simple, and can be fabricated at the wafer level over large areas, possessing excellent practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the lower electrode structure with surface field enhancement function proposed in the present invention. The lower electrode is processed on the substrate through semiconductor technology to form field enhancement structures such as step, spherical, serrated and comb shapes;

[0036] Figure 2 Schematic diagram of the operation of the bridge-structured air channel diode of Example 1;

[0037] Figure 3 Schematic diagram of the bridge-type air channel diode structure of Example 1;

[0038] Figure 4 Schematic diagram of the bridge-type air channel diode structure of Example 2;

[0039] Figure 5 Schematic diagram of the bridge-type air channel diode structure of Example 3;

[0040] Figure 6 Schematic diagram of the bridge-type air channel diode structure of Example 4;

[0041] Figure 7 Schematic diagram of the bridge-type air channel diode structure of Example 5;

[0042] Figure 8 The preparation method of the bridge structure air channel diode of Example 1;

[0043] Figure 9The preparation method of the bridge structure air channel diode of Example 2;

[0044] Figure 10 The preparation method of the bridge structure air channel diode of Example 3;

[0045] Figure 11 The preparation method of the bridge structure air channel diode of Example 4;

[0046] Figure 12 The preparation method of the bridge structure air channel diode of Example 5;

[0047] Reference numerals:

[0048] 1. Substrate, 2. Lower electrode, 53. Bridge metal upper electrode, 6. Nano air channel, 51. First metal conductive layer,

[0049] 55. Second metal conductive layer, 61. First nanometer air channel, 62. Second nanometer air channel, 21. First lower electrode, 22. Second lower electrode, 32. Dielectric sacrificial layer. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0051] Example 1

[0052] like Figure 3 As shown, this embodiment provides a bridge-type air channel diode, comprising a silicon substrate and a first metal layer, a second metal layer, and a metal electrode structure disposed on the upper surface of the silicon substrate. The electrode structure is located between the first metal layer and the second metal layer; it comprises a metal lower electrode and a bridge-type metal upper electrode; the bridge-type metal upper electrode is made of a conductive material capable of elastic deformation under an applied voltage, is coaxially sleeved outside the metal lower electrode, and a gap is left between the metal lower electrode to form an air channel. In this embodiment, the metal lower electrode is a trapezoidal structure with a thickness of 30nm; the air between the bridge-type metal upper electrode and the metal lower electrode is 60nm thick, and the metal conductive layer and the metal electrode structure together constitute a coplanar waveguide structure.

[0053] The working process of the device is as follows: Figure 2 As shown in the figure, a negative voltage is applied to the metal bottom electrode and a positive voltage is applied to the bridge metal top electrode. Under the action of the external electric field, electrons tunnel from the metal bottom electrode into the air channel and are collected by the bridge metal top electrode under the action of the external electric field. As the external bias increases, the bridge metal top electrode emits elastic deformation, and the gap between the upper and lower metal electrodes gradually decreases, thereby reducing the size of the air channel, increasing the electric field strength on the surface of the bottom electrode, and increasing the emission current.

[0054] like Figure 8 As shown, the method for preparing the bridge structure air channel diode of this embodiment includes the following steps:

[0055] S1. Spin-coat photoresist on a silicon substrate and pattern it using ultraviolet lithography. Then, deposit a 30nm thick metal conductive layer to naturally form a trapezoidal structure. Subsequently, remove the photoresist and the metal conductive layer thereon using acetone stripping, leaving only the metal bottom electrode on the silicon substrate.

[0056] S2. Deposit a 60nm thick SiO2 sacrificial dielectric layer on the upper surface of the structure obtained in S1 using an ALD process to completely cover the trapezoidal metal bottom electrode. At this point, a 60nm thick SiO2 sacrificial dielectric layer is formed on the trapezoidal metal bottom electrode. This sacrificial dielectric layer will determine the longitudinal dimensions of the device's micro-nano air channel and serve as an isolation dielectric between the upper and lower electrodes before release.

[0057] S3, selectively removing the dielectric sacrificial layer on the structure obtained in S2 through an overlay process, leaving only the sacrificial layer covering the lower metal electrode, thereby determining the lateral size of the air channel;

[0058] S4. Perform secondary photolithography on the structure obtained in S3 to form a bridge-type metal upper electrode and two metal conductive layers, each of which has a thickness of 400 nm. The bridge-type metal upper electrode and the metal lower electrode together constitute an electrode structure, and the two metal conductive layers are located on both sides of the electrode structure, and the three metal conductive layers do not contact each other.

[0059] S5. Etching is performed using a BOE solution to completely remove the dielectric sacrificial layer between the metal lower electrode and the bridge-type metal upper electrode to form a nano-air channel 6.

[0060] Example 2

[0061] like Figure 4As shown, a bridge-structured air channel diode includes a silicon substrate and a first metal layer, a second metal layer, and an electrode structure arranged on the upper surface of the silicon substrate. The electrode structure is located between the first metal layer and the second metal layer; it includes a first metal lower electrode, a second metal lower electrode, and a bridge-type upper electrode. The first metal lower electrode and the second metal lower electrode are arranged in parallel and do not contact each other. The bridge-type metal upper electrode simultaneously covers the first metal lower electrode and the second metal lower electrode. There is a gap between the first metal lower electrode and the bridge-type metal upper electrode, and between the second metal lower electrode and the bridge-type metal upper electrode, and the two gaps are not connected to each other. The gap between the first metal electrode and the bridge-type metal upper electrode forms a first air channel, and the gap between the second metal lower electrode and the bridge-type metal upper electrode forms a second air channel. In this embodiment, the two metal lower electrodes both adopt a trapezoidal structure and have the same thickness of 30nm. The thickness of the two air channels is 70nm. The metal conductive layer electrode structure together forms a coplanar waveguide structure.

[0062] The device operates as follows: Two metal bottom electrodes are applied with equal or different negative voltages, while a positive voltage is applied to the metal top electrode in a bridge structure. Under the action of an external electric field, electrons tunnel from the metal bottom electrodes into the air channel and are collected by the metal top electrode under the action of the external electric field. Because the voltage applied to the bridge top electrode is the same, the emission of each bottom electrode can be independently controlled by changing the bias voltage on each bottom electrode, thus realizing the function of the array.

[0063] like Figure 9 As shown, the method for preparing the bridge structure air channel diode of this embodiment includes the following steps:

[0064] S1. Spin-coating photoresist on an intrinsic silicon substrate 1 and patterning it using ultraviolet lithography is followed by depositing a 30 nm thick metal conductive layer to naturally form a trapezoidal structure. Then, stripping the photoresist and the metal conductive layer thereon using acetone is performed, leaving only the first metal bottom electrode and the second metal bottom electrode on the insulating silicon substrate.

[0065] S2. Deposit a 70nm thick Al2O3 dielectric layer 4 on the wafer using an ALD process to completely cover the two metal bottom electrodes. At this point, a 70nm thick Al2O3 dielectric sacrificial layer is formed. The thickness of this dielectric sacrificial layer will determine the longitudinal dimensions of the device's micro-nano air channel and serve as an isolation dielectric between the upper and lower electrodes before release.

[0066] S3, selectively removing the excess dielectric sacrificial layer on the structure obtained in S2 by an overlay process and determining the lateral size of the air channel, leaving only the dielectric sacrificial layer used to cover the two metal bottom electrodes;

[0067] S4: Perform secondary photolithography to pattern two metal layers and a bridge-type metal upper electrode on the structure obtained in S3, and then deposit them. The bridge-type metal upper electrode completely covers the first metal lower electrode and the second metal lower electrode. Tungsten metal is used for the two metal layers, and the deposition thickness is 400nm.

[0068] S5 , performing etching with a BOE solution to completely remove the dielectric sacrificial layer between the first metal lower electrode, the second metal lower electrode, and the bridge metal upper electrode to form a nanometer air channel 6 .

[0069] Example 3

[0070] like Figure 5 As shown, this embodiment provides an ITO substrate and a first metal layer, a second metal layer and a metal electrode structure arranged on the upper surface of the ITO substrate. The electrode structure is located between the first metal layer and the second metal layer; it includes a metal lower electrode and a bridge-type metal upper electrode; the bridge-type metal upper electrode is made of a conductive material that can undergo elastic deformation under an external voltage, is coaxially sleeved outside the metal lower electrode, and leaves a gap between the metal lower electrode and the metal lower electrode to form an air channel. In this embodiment, the metal lower electrode is a spherical metal lower electrode formed by self-assembly of a 70nm silver thin film. The unique curvature of the spherical structure is used to change its surface electric field strength and increase the emission current. The thickness of the air between the bridge-type metal upper electrode and the metal lower electrode is 120nm nm. The metal conductive layer and the metal electrode structure together constitute a coplanar waveguide structure.

[0071] The device operates as follows: a voltage is applied between the upper and lower metal electrodes. Under the influence of the applied electric field, electrons tunnel from the metal electrode into the air channel, where they are collected by the metal electrode under the influence of the applied electric field. As the applied bias voltage increases, the gap between the upper and lower electrodes gradually decreases due to the elastic deformation of the bridge-type upper electrode, thereby reducing the size of the air channel, increasing the electric field strength on the electrode surface, and increasing the emission current.

[0072] like Figure 10 As shown, a bridge-structured air channel diode of this embodiment has a preparation method comprising the following steps:

[0073] S1, spin-coating a photoresist on an ITO substrate and patterning it using ultraviolet lithography, then preparing a 70 nm thick metal conductive layer by magnetron sputtering a silver material; then, removing the photoresist and the metal conductive layer thereon by acetone stripping, leaving only the metal conductive layer 21 on the ITO substrate;

[0074] S2. The sputtered silver film is annealed in an Ar atmosphere at 300° C. for 20 minutes to allow the silver film on the substrate surface to self-assemble into a spherical metal bottom electrode;

[0075] S3. Deposit a 120nm thick Al2O3 dielectric layer on the upper surface of the structure obtained in S2 using an ALD process. A 120nm thick Al2O3 sacrificial dielectric layer is formed on the spherical metal lower electrode 22. The thickness of this insulating layer determines the longitudinal dimensions of the device's micro-nano air channel and serves as an insulating dielectric between the upper and lower electrodes before release.

[0076] S4, selectively removing the redundant dielectric sacrificial layer on the structure obtained in S2 by an overlay process, and determining the lateral size of the air channel;

[0077] S5. Perform secondary photolithography on the structure obtained in S4 to produce a bridge-type metal upper electrode and two metal conductive layers. The thickness of the two metal conductive layers is 400 nm and the material used is tungsten metal. The bridge-type metal upper electrode and the metal lower electrode together constitute an electrode structure. The two metal conductive layers are located on both sides of the electrode structure and do not contact each other.

[0078] S6. Use BOE solution to perform etching to completely remove the dielectric sacrificial layer between the spherical metal lower electrode and the bridge metal upper electrode to form a nano air channel.

[0079] Example 4

[0080] like Figure 6 As shown, the present embodiment provides a bridge-type air channel diode, comprising a sapphire substrate and a first metal layer, a second metal layer, and a metal electrode structure arranged on the upper surface of the sapphire substrate. The electrode structure is located between the first metal layer and the second metal layer; it comprises a metal lower electrode and a bridge-type metal upper electrode; the bridge-type metal upper electrode is made of a conductive material that can undergo elastic deformation under an external voltage, is coaxially sleeved outside the metal lower electrode, and leaves a gap between the metal lower electrode and the metal lower electrode to form an air channel. In this embodiment, the metal lower electrode is a comb-like structure, and the use of a comb-like structure can also enhance the electric field on the surface of the lower electrode. The thickness of the air between the bridge-type metal upper electrode and the metal lower electrode is 150nm, and the metal conductive layer and the metal electrode structure together constitute a coplanar waveguide structure.

[0081] The device operates as follows: a negative voltage is applied to the metal lower electrode, while a positive voltage is applied to the bridge-structured metal upper electrode. Under the influence of an external electric field, electrons tunnel from the metal lower electrode into the air channel, where they are collected by the metal upper electrode under the influence of the external electric field. As the applied bias voltage increases, the bridge-structured upper electrode undergoes elastic deformation, gradually reducing the gap between the upper and lower electrodes. This reduces the size of the air channel, increases the electric field strength on the lower electrode surface, and increases the emission current.

[0082] like Figure 11 As shown, a method for preparing a bridge-type air channel diode of this embodiment includes the following steps:

[0083] S1, forming a 100 nm thick metal conductive layer by evaporation on a sapphire substrate;

[0084] S2. Etching the metal conductive layer using EBL to separate the metal into isolated metal strips.

[0085] S3, using FIB etching to etch the middle metal strip to form a comb-shaped metal bottom electrode;

[0086] S4. Deposit a 150nm thick SiO2 dielectric layer on the structure obtained in S3 using an ALD process to completely cover the comb-shaped metal bottom electrode 25. At this point, a 150nm thick SiO2 dielectric sacrificial layer is formed on the comb-shaped metal bottom electrode 25. The thickness of this isolation layer will determine the longitudinal dimensions of the micro-nano air channel of the device and will serve as an isolation dielectric between the upper and lower electrodes before release.

[0087] S5, selectively removing the dielectric sacrificial layer on the structure obtained in S3 by an overlay process and determining the lateral size of the air channel;

[0088] S6. Perform secondary photolithography on the structure obtained in S5 to produce a bridge-type metal upper electrode and two metal conductive layers. The thickness of the two metal conductive layers is 300 nm. The bridge-type metal upper electrode is made of tungsten metal. The bridge-type metal upper electrode and the metal lower electrode together constitute an electrode structure. The two metal conductive layers are located on both sides of the electrode structure, and the three metal conductive layers do not contact each other.

[0089] S7. Use BOE solution to perform etching to completely remove the dielectric sacrificial layer in the comb-shaped metal lower electrode and the bridge-type metal upper electrode to form a nano-air channel.

[0090] Example 5

[0091] like Figure 7 As shown, the present embodiment provides a bridge-type air channel diode, comprising a sapphire substrate and a first metal layer, a second metal layer, and a metal electrode structure arranged on the upper surface of the sapphire substrate. The electrode structure is located between the first metal layer and the second metal layer; it comprises a metal lower electrode and a bridge-type metal upper electrode; the bridge-type metal upper electrode is made of a conductive material that can undergo elastic deformation under an applied voltage, is coaxially sleeved outside the metal lower electrode, and leaves a gap between the metal lower electrode and the metal lower electrode to form an air channel. In this embodiment, the metal lower electrode is a trapezoidal structure with a thickness of 30nm; the thickness of the air channel between the bridge-type metal upper electrode and the metal lower electrode is 1000Å, and the contact surface with the bridge-type metal upper electrode adopts a right angle at the top and side connection, and the metal conductive layer and the metal electrode structure together constitute a coplanar waveguide structure.

[0092] The device operates as follows: a positive voltage is applied to the metal lower electrode, while a negative voltage is applied to the bridge-structured metal upper electrode. Under the influence of an external electric field, electrons tunnel from the metal upper electrode into the air channel, where they are collected by the metal lower electrode under the influence of the external electric field. As the applied bias voltage increases, the bridge-structured upper electrode undergoes elastic deformation, gradually reducing the gap between the upper and lower electrodes. This reduces the size of the air channel, increases the electric field strength on the upper electrode surface, and increases the emission current.

[0093] like Figure 12 As shown, in this embodiment, a bridge-structure air channel diode is thinned using chemical mechanical polishing to thin the dielectric sacrificial layer, including the following steps:

[0094] S1, spin-coating photoresist on the sapphire substrate and patterning it using UV lithography, and then depositing a 30 nm thick metal conductive layer 3;

[0095] S2, removing the photoresist and the metal conductive layer thereon by acetone stripping, leaving the metal bottom electrode formed by the conductive layer 32 on the sapphire substrate;

[0096] S3. Deposit a 2 μm thick SiO2 dielectric layer on the structure obtained in S2 by PEVCD process, so that the dielectric layer completely covers the metal bottom electrode 32. Then, use chemical mechanical polishing to thin the SiO2 so that its thickness on the metal bottom electrode 32 does not exceed 100 nanometers.

[0097] S4. The dielectric sacrificial layer on the wafer structured in S2 is selectively removed by overlaying, leaving only the sacrificial layer covering the lower metal electrode, thereby determining the lateral dimensions of the air channel. Subsequently, a secondary photolithography process is performed to pattern the bridge-type metal upper electrode, completing the coplanar waveguide (CPW) structure and depositing a 350nm thick metal conductive layer.

[0098] S5. Use BOE solution to perform etching to completely remove the dielectric sacrificial layer in the metal lower electrode 32 and the bridge-type metal upper electrode 53 to form a micro-nano air channel.

[0099] From the above, it can be seen that the present invention provides a bridge-structured air channel diode, which covers the lower electrode with a bridge-type upper electrode, and cooperates with the completely removed dielectric sacrificial layer to make the upper and lower electrodes overlap and align naturally with each other in the vertical space. On the one hand, it improves the problems of traditional vertical structure micro-nano air channel devices such as difficult to control electronic behavior and low electron collection efficiency; on the other hand, it avoids the influence of the quality of the dielectric sacrificial layer film on the voltage and functional tolerance of the device, and ensures the consistency of device performance. In actual use, the shape of the lower electrode is not limited, and only the upper surface of the lower electrode can be changed, or the entire shape of the lower electrode can be changed. Figure 1As shown, it can be trapezoidal, comb-shaped, sawtooth-shaped, spherical, etc. By controlling the shape of the lower electrode, the overlap area between electrodes can be reduced and field enhancement can be achieved.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A bridge-type air channel diode comprising a substrate and a first metal layer, a second metal layer, and an electrode structure coplanarly disposed on an upper surface of the substrate, characterized in that: The electrode structure is located between the first metal layer and the second metal layer along the substrate plane direction; it includes a lower electrode and a bridge-type upper electrode; the bridge-type upper electrode is made of a conductive material that can undergo elastic deformation under an external voltage, is coaxially sleeved outside the lower electrode, and leaves a gap between the lower electrode and the lower electrode to form an air channel.

2. The bridge-type air channel diode according to claim 1, characterized in that: The substrate material is an insulating material or a semiconductor material; the first metal layer and the second metal layer are both made of a conductive material.

3. The bridge-type air channel diode according to claim 1, characterized in that: The lower electrode material is a low-dimensional material such as metal, metalloid, transparent conductive film, graphene, or a semiconductor material.

4. The bridge-type air channel diode according to claim 1, characterized in that: The lower electrode is processed by using semiconductor micro-nano technology.

5. The bridge-type air channel diode according to claim 1, characterized in that: The lower electrode and the bridge-type upper electrode can both serve as electrodes for electron emission; when a negative bias is applied to the lower electrode and a positive bias is applied to the upper electrode, electrons are emitted from the lower electrode and collected by the bridge-type upper electrode; when a positive bias is applied to the lower electrode and a negative bias is applied to the bridge-type upper electrode, electrons are emitted from the bridge-type upper electrode and collected by the lower electrode.

6. The bridge-type air channel diode according to any one of claims 1 to 5, characterized in that: The lower electrode is in a trapezoidal, comb-like or spherical shape, and the surface electric field strength is enhanced by changing the shape of the lower electrode, thereby obtaining a larger current.

7. The bridge-structure air channel diode according to claim 1, characterized in that: There are multiple lower electrodes, which are arranged in parallel, and each electrode does not touch each other, and all electrodes are covered by the bridge-type upper electrode. A gap is left between each lower electrode and the bridge-type upper electrode to serve as an air channel, and all the air channels are not connected to each other.

8. The bridge-structure air channel diode according to claim 1, characterized in that: The size of the air channel is smaller than the mean free path of electron scattering in the air, which can ensure that the electrons are ballistically transported in the air without scattering.

9. The bridge-structure air channel diode according to claim 1, characterized in that: The preparation method of the bridge structure air channel diode comprises the following steps: S1. Forming a lower electrode on the upper surface of the substrate using a semiconductor process, wherein the lower electrode is located in the middle of the upper surface; S2, depositing a dielectric sacrificial layer on the upper surface of the structure obtained in S1, wherein the sacrificial layer covers the lower electrode; S3, selectively removing part of the dielectric sacrificial layer by an overlay process, leaving only the sacrificial layer covering the lower electrode; S4. Perform secondary photolithography on the upper surface of the structure obtained in S3 to form a bridge-type upper electrode and two metal conductive layers; the bridge-type upper electrode is coated on the remaining dielectric sacrificial layer, and the bridge-type upper electrode and the lower electrode together constitute an electrode structure, and the two metal conductive layers are located on both sides of the electrode structure, and the three metal conductive layers do not contact each other; S5. Use a wet etching or dry etching process to completely remove the dielectric sacrificial layer between the lower electrode and the bridge upper electrode to form an air channel.

10. The bridge-type air channel diode according to claim 9, characterized in that : The dielectric sacrificial layer material is a metal, insulator or semiconductor that can be released by wet etching or dry etching; the thickness of the dielectric sacrificial layer is greater than the thickness of the lower electrode.

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