A vertical nanometer air channel diode and its preparation method

Abstract

The present invention discloses a vertical nanometer air channel diode and its preparation method, belonging to the field of semiconductor device technology. The structure of the present invention comprises a substrate, a buffer layer, an emitter, a dielectric layer and a receiving electrode layer stacked in sequence from bottom to top; the emitter has a doping concentration of 10 18 cm ‑3 The above n-type highly doped gallium nitride or AlGaN / GaN heterojunction increases the number of carriers and improves the energy band characteristics through two-dimensional electron gas emission at the n-type highly doped gallium nitride or AlGaN / GaN heterojunction interface, achieving a lower turn-on voltage and a higher emission current. The fabrication process of the present invention utilizes conventional plasma-enhanced chemical vapor deposition, photolithography, electron beam evaporation, stripping, and dry etching techniques, without relying on high-precision and high-cost nanofabrication techniques. It offers advantages such as low cost and ease of integration, making it suitable for mass production of wafer-scale nanometer air channel diode arrays.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a vertical nanometer air channel diode and a preparation method thereof. Background Art

[0002] Thanks to advanced nano-manufacturing technology, nano-air channel devices (also known as nano-vacuum devices, nano-air gap devices, etc.) combine the characteristics of vacuum devices such as fast electron transit time and radiation resistance, with the advantages of solid-state transistors such as small scale, low power consumption, and easy integration. The electrons are transported ballistically at high speed and without scattering in an air channel that is smaller than its mean free path (about 68nm), which makes the device have broad application prospects in high frequency, high power, radiation resistance and other fields.

[0003] Figure 1 For traditional vertical structure nano air channel diodes, such as Figure 1 As shown in the figure, this structure controls the distance between the emitter and the receiver by controlling the thickness of the dielectric layer, thereby achieving precise control of the air channel length. Compared with planar structure nano-air channel devices that require complex processes, this vertical structure device has more advantages in precision control and manufacturing costs. However, since most of these devices are silicon-based, they usually use a surround gate structure or shorten the air channel length to improve device performance, and realize device functions through surface electron emission or two-dimensional electron gas emission. When used in high output current, ultra-fast response, and high-frequency application scenarios, their high voltage resistance, radiation resistance, and high temperature resistance characteristics still cannot meet the use requirements.

[0004] Materials such as gallium nitride (GaN) have low or even negative electron affinities. Through doping or bandgap and polarization manipulation, different barrier morphologies can be designed, facilitating high-density electron emission and increasing device output current. Furthermore, GaN exhibits stable physical and chemical properties, a wide bandgap, and excellent radiation and high-temperature resistance. Its heterostructures offer highly tunable properties. Combining these excellent properties of materials like GaN, the research on a vertical nano-air channel device and its fabrication method is of great significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a vertical nanometer air channel diode and its preparation method, which achieves a lower turn-on voltage and a larger emission current through two-dimensional electron gas emission from bulk materials or material heterojunctions. The air channel length is precisely controlled by regulating the thickness of the dielectric layer, without relying on expensive nano-processing equipment. It is low-cost, can be integrated, and can also be produced in large quantities.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A vertical nanometer air channel diode comprises a substrate, a buffer layer, an emitter, a dielectric layer and a receiver layer stacked in sequence from bottom to top;

[0008] The emitter has a doping concentration of 10 18 cm -3 The above n-type highly doped gallium nitride or AlGaN / GaN heterojunction includes a first semiconductor layer and a second semiconductor layer; the first semiconductor layer is a stepped structure consisting of a square substrate and a column stacked on the square substrate, and the second semiconductor layer is stacked on the column and has the same structure and size as the column, and a two-dimensional electron gas is formed at the connection interface between the two;

[0009] The structure and size of the dielectric layer and the receiving electrode layer are the same as those of the second semiconductor. After the second semiconductor layer, the dielectric layer and the receiving electrode layer are stacked together in sequence, an air channel is formed between the upper surface of the square substrate and the receiving electrode layer.

[0010] Furthermore, when the emitter is an AlGaN / GaN heterojunction, the material of the first semiconductor layer is gallium nitride GaN, and the material of the second semiconductor layer is aluminum gallium nitride AlGaN.

[0011] Furthermore, the material used for the substrate includes but is not limited to silicon, sapphire, silicon carbide, and gallium nitride.

[0012] Furthermore, the buffer layer material is an insulating material, preferably a carbon-doped high-resistance gallium nitride material.

[0013] Furthermore, the dielectric layer material is an insulating material, including but not limited to silicon dioxide, aluminum oxide or silicon nitride.

[0014] Furthermore, the thickness of the dielectric layer does not exceed 70 nm.

[0015] Furthermore, the receiving electrode layer material is metal, including but not limited to titanium / gold composite thin film electrode.

[0016] A method for preparing a vertical nanometer air channel diode comprises the following steps:

[0017] S1. Depositing a buffer layer and an emitter on a substrate in sequence by metal organic chemical vapor deposition (MOCVD); depositing a dielectric layer on the emitter by plasma enhanced chemical vapor deposition (PECVD); wherein the emitter includes a first semiconductor layer and a second semiconductor layer stacked on the first semiconductor layer;

[0018] S2. First, a receiving electrode pattern is prepared on the dielectric layer by using a photolithography method, and then a metal receiving electrode layer is deposited;

[0019] S3, using acetone to remove the photoresist and the metal thereon by a stripping process, leaving behind a patterned metal receiving electrode layer;

[0020] S4. Use the metal receiving electrode layer as a mask and adopt dry etching to remove the dielectric layer and part of the emitter layer outside the area covered by the metal receiving electrode layer, leaving only the metal receiving electrode pattern area and the dielectric layer and emitter layer thereunder, exposing the stacked heterostructure, so that the second semiconductor layer, the dielectric layer, and the receiving electrode layer are stacked together in sequence to form an air channel between the upper surface of the square substrate and the receiving electrode layer.

[0021] After adopting the above technical solution, the present invention has the following beneficial effects:

[0022] 1. The vertical nanometer air channel diode of the present invention is to use a doping concentration of 10 18 cm -3 The above two-dimensional electron gas emission at the n-type highly doped gallium nitride or AlGaN / GaN heterojunction interface increases the number of carriers and improves the energy band characteristics; achieving a lower turn-on voltage and a larger emission current.

[0023] 2. The vertical nanometer air channel diode of the present invention has an air channel length that is precisely controlled at the nanometer level by regulating the thickness of the dielectric layer. Its size is close to or lower than the mean free path of electrons. The device can operate at atmospheric pressure without the need for vacuum conditions.

[0024] 3. The vertical nano-air channel diode of the present invention is prepared through conventional plasma-enhanced chemical vapor deposition, photolithography, electron beam evaporation, stripping, and dry etching processes, without relying on high-precision and high-cost nano-process preparation technology; it has the advantages of low cost and easy integration, and is suitable for mass production of wafer-level nano-air channel diode arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a traditional vertical structure nano air channel diode;

[0026] Figure 2 is a three-dimensional diagram of the vertical nano-air channel diode of Example 1;

[0027] Figure 3 A schematic diagram of the process flow of a method for preparing a vertical nanometer air channel diode based on a dry etching process proposed in the present invention;

[0028] Figure 4 Schematic diagram of electron transport in a vertical nanometer air channel diode according to an embodiment;

[0029] Reference numerals:

[0030] 1. Substrate layer; 2. Buffer layer; 3. First semiconductor layer; 3a. Unetched first semiconductor layer; 3b. Etched first semiconductor layer; 4. Second semiconductor layer; 5. Dielectric layer; 6. Receiver layer; 61. Receiver layer; 62. Receiver layer; 63. Receiver layer; 101. Photoresist; 102. Photoresist. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the technical solutions, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and Examples. It should be noted that the following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. It should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the claims appended hereto.

[0032] Example 1

[0033] like Figure 2 As shown, a vertical nanometer air channel diode provided by this embodiment includes a substrate 1, a buffer layer 2, an emitter, a dielectric layer 5 and a receiving electrode layer 6 stacked in sequence from bottom to top.

[0034] The emitter comprises a first semiconductor layer 3 and a second semiconductor layer 4; the first semiconductor layer 3 is a stepped structure consisting of a square substrate 3a and a column 3b superimposed on the square substrate, and the second semiconductor layer 4 is stacked on the column, and its structure and size are the same as the column 3b, and a two-dimensional electron gas is formed at the interface between the two. 18 cm -3 The above-mentioned highly doped gallium nitride structure, gallium nitride or gallium arsenide multilayer heterostructure can also be made of other semiconductor materials. Gallium nitride has many advantages in field emission materials, such as low electron affinity (2.7-3.3eV), good physical and chemical stability, large band gap (3.4eV) and high breakdown field strength (3.3MV / cm). In addition, AlGaN / GaN heterostructure can form a surface density of 1×10 due to the polarization effect under undoped conditions. 13 cm -2 The two-dimensional electron gas (2DEG) not only increases electron density but also improves the band distribution at the interface, providing excellent field emission characteristics with high current density and low turn-on voltage. In this embodiment, an AlGaN / GaN heterojunction is preferably used as the emitter to achieve excellent field emission performance. The first semiconductor layer of the heterojunction is made of gallium nitride (GaN), and the second semiconductor layer is made of aluminum gallium nitride (AlGaN).

[0035] The structure and size of the dielectric layer 5 and the receiving electrode layer are the same as those of the second semiconductor 4; after the second semiconductor 4, the dielectric layer 5, and the receiving electrode layer 6 are stacked together in sequence, an air channel is formed between the upper surface of the square substrate 3a and the receiving electrode layer 6 to achieve ballistic transport of electrons under atmospheric pressure.

[0036] In this embodiment, the substrate 1 can be made of materials such as silicon, sapphire, silicon carbide, and gallium nitride, preferably silicon carbide. The buffer layer 2 utilizes carbon-doped high-resistance gallium nitride. The dielectric layer 5 utilizes insulating materials including, but not limited to, silicon dioxide, aluminum oxide, and silicon nitride, with a thickness not exceeding 70 nm. The receiving electrode layer 6 is made of a metal material, preferably a titanium / gold composite thin film electrode.

[0037] When in use, AlGaN / GaN heterostructures will form a surface density of up to 10 due to spontaneous polarization and piezoelectric polarization effects on the GaN side close to AlGaN without external bias. 13 cm -3 The high-density two-dimensional electron gas (2DEG) with Coulomb repulsion between electrons at high concentrations modulates the band structure of the heterostructure-air interface, resulting in a low electron affinity. When a forward bias is applied to the receiver 6, the strong electric field pulls down and thins the barrier between the heterostructure and air, allowing electrons from the 2DEG to easily tunnel through the interface barrier to the air channel. There, they move against the direction of the electric field before being captured by the receiver, completing electron transport from the emitter to the receiver. When a reverse bias is applied to the receiver, the strong electric field near the receiver pulls down and thins the interface barrier between the receiver and air. Electrons from the receiver tunnel through the thin interface barrier to the air channel, then move against the direction of the electric field before being captured by the heterostructure, completing electron transport under reverse bias conditions.

[0038] like Figure 3 As shown, this embodiment also provides a method for preparing the vertical nanometer air channel diode, comprising the following steps:

[0039] S1. A buffer layer 2 and an emitter are sequentially deposited on a substrate 1 by metal organic chemical vapor deposition (MOCVD); a dielectric layer 5 is deposited on the emitter by plasma enhanced chemical vapor deposition (PECVD); wherein the emitter comprises a first semiconductor layer 3 and a second semiconductor layer 4 stacked on the first semiconductor layer 3; the materials used for each layer are as follows: sapphire is used for the substrate layer 1; the buffer layer 2 is an insulating material, preferably a carbon-doped high-resistance gallium nitride material; an AlGaN / GaN heterojunction is used for the emitter; the dielectric layer 5 is an insulating material, preferably aluminum oxide in this embodiment.

[0040] S2, firstly prepare a receiving electrode pattern on the dielectric layer 5 by photolithography, and then deposit a metal electrode layer;

[0041] S3, using acetone to remove the photoresist and the metal thereon using a stripping process, leaving the patterned metal receiving electrode layer 6;

[0042] S4. Use the metal receiving electrode layer 6 as a mask and adopt a dry etching method to etch the dielectric layer to remove the dielectric layer 5 and part of the emitter layer outside the protection area of ​​the metal receiving electrode layer 6, leaving only the metal receiving electrode pattern area and the dielectric layer 5 and emitter layer below it, exposing the stacked heterostructure; the second semiconductor 4, the dielectric layer 5, and the receiving electrode layer 6 are stacked together in sequence to form an air channel between the upper surface of the square substrate 3a and the receiving electrode layer.

[0043] Figure 4 FIG. 1 is a schematic diagram of electron transport of a vertical nanometer air channel diode according to an embodiment of the present invention. Figure 3 As shown in the figure, when a forward bias voltage (V) is applied between the receiver and emitter of the vertical nanometer air channel diode, in addition to the 2DEG generated by spontaneous polarization in the AlGaN / GaN heterojunction, the concentration of the 2DEG is greatly increased due to piezoelectric polarization. Electrons pass from the emitter to the receiver through the air channel, and accordingly, current (I) flows from the receiver to the emitter. When a reverse bias voltage is applied between the receiver and emitter of the diode, the metal receiver will act as a cathode to emit electrons, and the emitter will act as an anode to receive electrons, and the current will flow in opposite directions. This shows that the vertical nanometer air channel diode of this embodiment can achieve a lower turn-on voltage and a larger emission current.

Claims

1. A vertical nanometer air channel diode, comprising a substrate, a buffer layer, an emitter, a dielectric layer, and a receiver layer stacked sequentially from bottom to top, characterized in that: The emitter is an AlGaN / GaN heterojunction, comprising a first semiconductor layer and a second semiconductor layer. The first semiconductor layer is made of gallium nitride (GaN) and the second semiconductor layer is made of aluminum gallium nitride (AlGaN). The first semiconductor layer is a stepped structure consisting of a square substrate and a column stacked on the square substrate. The second semiconductor layer is stacked on the column and has the same structure and dimensions as the column. A two-dimensional electron gas is formed at the interface between the two. The structure and size of the dielectric layer and the receiving electrode layer are the same as those of the second semiconductor. After the second semiconductor layer, the dielectric layer and the receiving electrode layer are stacked together in sequence, an air channel is formed between the upper surface of the square substrate and the receiving electrode layer.

2. The vertical nanometer air channel diode according to claim 1, characterized in that: The substrate is made of silicon, sapphire, silicon carbide or gallium nitride.

3. The vertical nanometer air channel diode according to claim 1, characterized in that: The buffer layer material is a carbon-doped high-resistance gallium nitride material.

4. The vertical nanometer air channel diode according to claim 1, characterized in that: The dielectric layer is made of silicon dioxide, aluminum oxide or silicon nitride.

5. The vertical nanometer air channel diode according to claim 1, characterized in that: The thickness of the dielectric layer does not exceed 70 nm.

6. The vertical nanometer air channel diode according to any one of claims 1 to 5, characterized in that: The receiving electrode layer material is titanium / gold composite film.

7. A method for preparing a vertical nanometer air channel diode, comprising the steps of: S1. Depositing a buffer layer and an emitter on the substrate in sequence by using a metal organic chemical vapor deposition (MOCVD) method; depositing a dielectric layer on the emitter by using a plasma enhanced chemical vapor deposition (PECVD) method; The emitter includes a first semiconductor layer and a second semiconductor layer; the first semiconductor layer is stacked on the second semiconductor layer, the material of the first semiconductor layer is gallium nitride (GaN), and the material of the second semiconductor layer is aluminum gallium nitride (AlGaN); S2, first prepare a receiving electrode pattern on the dielectric layer by using a photolithography method, and then deposit a metal receiving electrode layer; S3, using acetone to remove the photoresist and the metal thereon by a stripping process, leaving behind a patterned metal receiving electrode layer; S4. Use the metal receiving electrode layer as a mask and adopt dry etching to remove the dielectric layer and part of the emitter layer outside the area covered by the metal receiving electrode layer, leaving only the metal receiving electrode pattern area and the dielectric layer and emitter layer thereunder, exposing the stacked heterostructure, so that the second semiconductor, the dielectric layer, and the receiving electrode layer are stacked together in sequence to form an air channel between the upper surface of the square substrate and the receiving electrode layer.

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