Low-voltage GaN radio frequency device with self-aligned electrode contact wall structure and preparation method of low-voltage GaN radio frequency device
By using the self-aligning electrode contact wall structure and magnetron sputtering to form the reactive metal layer in GaN radio frequency devices, the problems of on-resistance and knee voltage at low operating voltage are solved, efficient output power density and power additional efficiency are achieved, and the process is simplified to suit large-scale production.
Patent Information
- Application Number
- CN202411940915.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-04
AI Technical Summary
Existing GaN RF devices are difficult to effectively reduce the on-resistance and knee voltage at low operating voltage, resulting in low output power density and power additive efficiency.
A low-voltage GaN radio frequency device design adopts a self-aligning electrode contact wall structure. By setting an electrode contact wall on the AlGaN/GaN heterojunction epitaxial layer and using magnetron sputtering technology to form a reactive metal layer such as TiN or TaN, simplifying the process and reducing the on-resistance.
It realizes high output power density and power additional efficiency at low operating voltages, and the process is simple and suitable for large-scale production.
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Figure CN119767731A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a low-voltage GaN radio frequency device with a self-aligned electrode contact wall and a preparation method thereof. Background Art
[0002] Gallium nitride high electron mobility transistors have made remarkable progress in the fields of radar, satellite communications, mobile communication base stations, etc., and have provided excellent output performance due to their wide bandgap, high electron velocity, large two-dimensional electron gas density, high critical breakdown field strength and other characteristics. In the field of mobile terminals, RF devices need to work at low voltage. Compared with traditional GaAs RF devices, GaN RF devices can provide higher power added efficiency and lower power consumption at low operating voltage, making GaN technology competitive in the field of low-voltage RF.
[0003] In order to improve the output power density and power added efficiency of the device at low operating voltage, it is necessary to increase the maximum output current density of the device and reduce the on-resistance and knee voltage. By using AlN or InAlN barrier layers with higher 2DEG density and lower material contact resistance, the access resistance of the device can be reduced (S Liu, et al. Improved Breakdown Voltage and Low Damage E-Mode Operation of AlON / AlN / GaN HEMTs Using Plasma Oxidation Treatment[J]. IEEE Electron Device Letters, 2022, 43(10): 1621-1624. Qin J, Zhou QB, Liao BY, Chen JX, Wang H. A Comprehensive Analysis of the 2-DEG Transport Properties in In x Al 1-xN / AlN / GaN Heterostructure: Experiments and Numerical Simulations. IEEE Transactions on Electron Devices, 2020, 67(12): 5427-5433.). In addition, the ohmic metal process is optimized (H Sun, MH Liu, P Liu, et al. Optimization of Au-free ohmic contact based on the gate-first double-metal AlGaN / GaN MIS-HEMTsand SBDs process[J]. IEEE Transactions on Electron Devices, 2018, 65(2): 622-628.) and the re-growth of n + GaN technology can also effectively reduce R on (YW Zhou, MH Mi, M Yang, et al. High performance millimeter-wave InAlN / GaN HEMT for low voltage RF applications via regrown Ohmic contact with contact ledge structure [J]. Applied Physics Letters, 2022, 120(6):062104.).
[0004] However, the above methods have difficulties in epitaxial layer growth and additional process steps introduced by complex structures. Therefore, finding a simple, reliable, low-cost technology that can reduce device on-resistance and knee voltage and improve output power density and power added efficiency is an urgent problem to be solved for low-voltage RF devices. Summary of the invention
[0005] The purpose of the present invention is to reduce the on-resistance and knee voltage of GaN radio frequency devices, improve their power density and power added efficiency at low operating voltages, and propose a low-voltage GaN radio frequency device with an electrode contact wall structure and a preparation method thereof from the perspective of device structure design. The process is simple and can meet the needs of large-scale production with high efficiency and high yield.
[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.
[0007] Self-aligned electrode contact wall structure low voltage GaN RF device, including AlGaN / GaN heterojunction epitaxial layer;
[0008] The AlGaN / GaN heterojunction epitaxial layer is a planar structure;
[0009] A cap layer is grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer, and a source electrode and a drain electrode are respectively arranged on both sides of the upper surface of the AlGaN / GaN heterojunction epitaxial layer;
[0010] Electrode contact walls are provided on both sides of the source electrode and the drain electrode on the upper surface of the AlGaN / GaN heterojunction epitaxial layer, and on both sides of the upper surface of the source electrode and the drain electrode;
[0011] A gate electrode is disposed on the upper surface of the cap layer.
[0012] Furthermore, the gate electrode includes a Ni layer and an Au layer stacked from bottom to top; the gate electrode is vertically arranged on the upper surface of the cap layer; the thickness is defined as the distance between the upper surface and the lower surface of the AlGaN / GaN heterojunction epitaxial layer; the thickness of the Ni layer and the Au layer in the gate electrode are 20-50nm and 200-400nm respectively; the length is defined as the distance between the upper surfaces of the AlGaN / GaN heterojunction epitaxial layer; the distance between the gate electrodes on the upper surfaces of the AlGaN / GaN heterojunction epitaxial layer, that is, the length is 80-300nm.
[0013] Furthermore, the thickness of the AlGaN / GaN heterojunction epitaxial layer is 600-1000 μm, the cap layer is GaN or SiN, and the thickness of the cap layer is 2-5 nm.
[0014] Further, the source electrode and the drain electrode include a Ti layer, an Al layer, a Ni layer and an Au layer stacked sequentially from bottom to top;
[0015] The thicknesses of the Ti layer, Al layer, Ni layer, and Au layer are 10-25 nm, 80-110 nm, 5-10 nm, and 80-110 nm, respectively;
[0016] The spacing between the source electrode and the drain electrode is 1-2 μm.
[0017] Furthermore, the cap layer includes GaN or SiN; and the length of the cap layer is 2 nm.
[0018] Furthermore, the electrode contact wall comprises TiN, TaN, TiN / TiSi x Stacked or TaN / TaSi x Lamination;
[0019] If the cap layer is GaN, the electrode contact wall is a reactive metal layer TiN generated by the reaction of magnetron sputtered metal Ti and nitrogen, or the electrode contact wall is a reactive metal layer TaN generated by the reaction of magnetron sputtered metal Ta and nitrogen;
[0020] If the cap layer is SiN, the electrode contact wall is a reactive metal layer TiN / TiSi generated by the reaction of magnetron sputtered metal Ti with nitrogen and SiN. x The stack, or electrode contact wall, is a reactive metal layer TaN / TaSi generated by the reaction of magnetron sputtered metal Ta with nitrogen and SiN x Overlay.
[0021] Furthermore, the extended length of the electrode contact wall on both sides of the source electrode and the drain electrode, that is, the length of the contact portion of the electrode contact wall (5) with the upper surface of the cap layer (2) is 0.4-0.8 μm;
[0022] The electrode contact walls on both sides of the source electrode and the drain electrode are symmetrically arranged about the source electrode and the drain electrode, and the electrode contact walls on both sides of the upper surface of the source electrode and the drain electrode are symmetrically arranged about the center of the upper surface of the source electrode and the drain electrode; the electrode contact walls cover the upper surface and side of the source electrode or the drain electrode.
[0023] The method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure comprises the following steps:
[0024] S1. Preparation and cleaning of AlGaN / GaN heterojunction epitaxial layer: Prepare AlGaN / GaN heterojunction epitaxial layer by metal organic vapor deposition MOCVD, then immerse the AlGaN / GaN heterojunction epitaxial layer in an acidic solution to remove the surface oxide layer, and then use an organic solvent to remove organic matter on the AlGaN / GaN heterojunction epitaxial layer;
[0025] Wherein, the cap layer on the upper surface of the AlGaN / GaN heterojunction epitaxial layer is GaN or SiN grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer when the AlGaN / GaN heterojunction epitaxial layer is grown by a metal organic compound chemical vapor deposition device, or SiN grown by a plasma enhanced chemical vapor deposition device after the AlGaN / GaN heterojunction epitaxial layer is cleaned;
[0026] S2. Source and drain electrodes and preparation: define the metal position and pattern of the source and drain electrodes by negative photolithography, and deposit the metal stack of the source and drain electrodes by electron beam deposition;
[0027] S3, electrode contact wall preparation: Based on step S2, without stripping the source electrode and drain electrode metal, Ti or Ta metal is continuously deposited on the position of the source electrode and drain electrode metal stack by magnetron sputtering, and after stripping, annealing is performed in a nitrogen atmosphere to form a TiN / TiSi x Stacked or TaN / TaSi x The stacked reactive metal layer; removing the excess reactive metal layer in the middle area of the upper surface of the source electrode and the drain electrode by inductively coupled plasma etching technology to form an electrode contact wall;
[0028] S4. Prepare the gate electrode by stripping process: Use a photolithography machine to expose the gate electrode pattern between the source electrode and the drain electrode, and then deposit a gate electrode material layer on the upper surface of the cap layer between the source electrode and the drain electrode by electron beam evaporation to prepare a Ni / Au gate electrode by stripping.
[0029] Further, in step S3, the thickness of Ti or Ta metal deposited on the source electrode and drain electrode metal layers by magnetron sputtering is 10-50 nm, and the length of the deposited Ti or Ta metal on the left and right sides of the source electrode and the drain electrode is 0.4-0.8 μm;
[0030] In a nitrogen atmosphere, annealing is performed at a temperature of 800°C-900°C for a time range of 30-90 seconds, so that the source electrode and the drain electrode form an ohmic contact with the AlGaN / GaN heterojunction epitaxial layer, and the magnetron sputtered metal Ti or Ta reacts with nitrogen to generate a reactive metal layer; the excess reactive metal layer in the middle area on the upper surface of the source electrode and the drain electrode is removed by inductively coupled plasma etching technology to form an electrode contact wall.
[0031] Further, when the cap layer is GaN, the reactive metal layer generated by the reaction of magnetron sputtered metal Ti and nitrogen is TiN, forming an electrode contact wall, or the reactive metal layer generated by the reaction of magnetron sputtered metal Ta and nitrogen is TaN, forming an electrode contact wall;
[0032] When the cap layer is SiN, the reaction metal layer formed by the magnetron sputtering of metal Ti, nitrogen and SiN is TiN / TiSi x The stacking forms the electrode contact wall, or the reaction metal layer formed by the magnetron sputtering of metal Ta and nitrogen and SiN is TaN / TaSi x The layers are stacked to form electrode contact walls.
[0033] Compared with the prior art, the present invention has the following beneficial effects and advantages:
[0034] Compared with conventional techniques such as regrowth of n+GaN electrode contact walls, the GaN RF device with a self-aligned electrode contact wall structure prepared by the present invention has a simple process, can achieve deep submicron source-drain spacing and low on-resistance, and is suitable for batch and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 is a flow chart of a method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure in an embodiment of the present invention;
[0036] Figure 2 is a schematic diagram of an epitaxial layer (1) and a cap layer (2) in an embodiment of the present invention;
[0037] Figure 3 is a schematic diagram of a source electrode (3) and a drain electrode (4) after growing on an epitaxial layer (1) and a cap layer (2) in an embodiment of the present invention;
[0038] Figure 4 In the embodiment of the present invention Figure 3 Schematic diagram of the self-aligned electrode contact wall (5) after growth on the base;
[0039] Figure 5 In the embodiment of the present invention Figure 4 Schematic diagram of the structure of a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure after a gate electrode (6) is grown on the foundation
[0040] Figure 6 Schematic diagram of output characteristic curve of low-voltage GaN radio frequency device with self-aligned electrode contact wall structure in an embodiment of the present invention;
[0041] Figure 7 It is a schematic diagram of large signal output power and efficiency of a device without electrode contact wall and a device with electrode contact wall in an embodiment of the present invention. DETAILED DESCRIPTION
[0042] The specific implementation of the present invention is further described below in conjunction with the drawings and embodiments, but the implementation and protection of the present invention are not limited thereto. It should be pointed out that any processes or process parameters that are not particularly described in detail below can be implemented by those skilled in the art with reference to the prior art.
[0043] Embodiment 1:
[0044] Self-aligned electrode contact wall structure low voltage GaN RF devices, such as Figure 5 As shown, it includes an AlGaN / GaN heterojunction epitaxial layer 1;
[0045] The AlGaN / GaN heterojunction epitaxial layer 1 is a planar structure;
[0046] A cap layer 2 is grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1, and a source electrode 3 and a drain electrode 4 are respectively arranged on both sides of the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1;
[0047] Electrode contact walls 5 are provided on both sides of the source electrode 3 and the drain electrode 4 on the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1, and on both sides of the upper surface of the source electrode 3 and the drain electrode 4;
[0048] A gate electrode 6 is disposed on the upper surface of the cap layer 2 .
[0049] Furthermore, the gate electrode 6 includes a Ni layer and an Au layer stacked from bottom to top; the gate electrode 6 is vertically arranged on the upper surface of the cap layer 2; the thickness is defined as the distance between the upper surface and the lower surface of the AlGaN / GaN heterojunction epitaxial layer 1; the thickness of the Ni layer and the Au layer in the gate electrode 6 are 20nm and 400nm respectively; the length is defined as the distance between the upper surfaces of the AlGaN / GaN heterojunction epitaxial layer 1; the distance between the gate electrodes 6 on the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1, that is, the length is 300nm.
[0050] In this embodiment, the thickness of the AlGaN / GaN heterojunction epitaxial layer 1 is 800 μm, the cap layer 2 is GaN or SiN, and the thickness of the cap layer 2 is 2-5 nm.
[0051] In this embodiment, the source electrode 3 and the drain electrode 4 include a Ti layer, an Al layer, a Ni layer and an Au layer stacked in sequence from bottom to top;
[0052] The thicknesses of the Ti layer, Al layer, Ni layer, and Au layer are 20 nm, 100 nm, 10 nm, and 100 nm, respectively;
[0053] In this embodiment, the distance between the source electrode 3 and the drain electrode 4 is 2 μm.
[0054] Furthermore, the cap layer 2 includes GaN or SiN; and the length of the cap layer 2 is 2 nm.
[0055] Furthermore, the electrode contact wall 5 comprises TiN, TaN, TiN / TiSi x Stacked or TaN / TaSi x Lamination;
[0056] If the cap layer 2 is GaN, the electrode contact wall 5 is a reactive metal layer TiN generated by the reaction of metal Ti and nitrogen generated by magnetron sputtering, or the electrode contact wall 5 is a reactive metal layer TaN generated by the reaction of metal Ta and nitrogen generated by magnetron sputtering;
[0057] If the cap layer 2 is SiN, the electrode contact wall 5 is a reactive metal layer TiN / TiSi generated by the reaction of metal Ti, nitrogen and SiN by magnetron sputtering. x The stack, or electrode contact wall 5, is a reactive metal layer TaN / TaSi generated by the reaction of magnetron sputtered metal Ta with nitrogen and SiN. x Overlay.
[0058] In this embodiment, the extension length of the electrode contact wall 5 on both sides of the source electrode 3 and the drain electrode 4 is 0.5 μm;
[0059] The electrode contact walls 5 on both sides of the source electrode 3 and the drain electrode 4 are symmetrically arranged about the source electrode 3 and the drain electrode 4, respectively, and the electrode contact walls 5 on both sides of the upper surfaces of the source electrode 3 and the drain electrode 4 are symmetrically arranged about the center of the upper surfaces of the source electrode 3 and the drain electrode 4, respectively; the electrode contact walls 5 cover the upper surface and side surfaces of the source electrode 3 or the drain electrode 4.
[0060] In this embodiment, a method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure is as follows: Figure 1 As shown, the following steps are included:
[0061] S1, such as Figure 2 As shown, the AlGaN / GaN heterojunction epitaxial layer 1 is prepared and cleaned: the AlGaN / GaN heterojunction epitaxial layer 1 is prepared by metal organic vapor deposition MOCVD, and then the AlGaN / GaN heterojunction epitaxial layer 1 is immersed in a H2SO4:H2O2=4:1 (mass ratio) solution for 20 minutes (H2SO4 and H2O2 are both commercially available) to remove the surface oxide layer, and then acetone and isopropanol are used to remove organic matter on the AlGaN / GaN heterojunction epitaxial layer 1;
[0062] Wherein, the cap layer 2 on the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1 is GaN or SiN grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer 1 when the GaN / GaN heterojunction epitaxial layer 1 is grown by a metal organic compound chemical vapor deposition device, or SiN grown by a plasma enhanced chemical vapor deposition device after the AlGaN / GaN heterojunction epitaxial layer 1 is cleaned;
[0063] S2, such as Figure 3 As shown, the source and drain electrodes 3 and 4 are prepared by defining the metal positions and patterns of the source electrode 3 and the drain electrode 4 by negative photolithography, and depositing Ti / Al / Ni / Au in sequence from bottom to top by electron beam evaporation;
[0064] S3, such as Figure 4 As shown, the electrode contact wall 5 is prepared: on the basis of step S2, the source electrode 3 and the drain electrode 4 metal are not stripped, and Ti metal is continuously deposited on the position of the source electrode 3 and the drain electrode 4 metal stack by magnetron sputtering. In this embodiment, the thickness of the deposited Ti metal is 20nm; in a nitrogen atmosphere, annealing is performed at a temperature of 850°C for 60 seconds, so that the source electrode 3 and the drain electrode 4 form an ohmic contact with the AlGaN / GaN heterojunction epitaxial layer 1, and the magnetron sputtered metal Ti reacts with nitrogen and the SiN cap layer to generate a reactive metal layer; after stripping, annealing is performed in a nitrogen atmosphere to form a TiN / TiSi xstack; remove the excess reactive metal layer in the middle region of the upper surface of the source electrode 3 and the drain electrode 4 by inductively coupled plasma etching technology to form an electrode contact wall 5; in this embodiment, the length of the electrode contact wall 5 on both sides of the source electrode 3 and the drain electrode 4 is 0.5μm
[0065] S4, such as Figure 5 As shown, the gate electrode 6 is prepared by a stripping process: a photolithography machine is used to expose the gate electrode 6 pattern between the source electrode 3 and the drain electrode 4, and then a Ni / Au thin film is deposited on the upper surface of the cap layer 2 between the source electrode 3 and the drain electrode 4 by electron beam evaporation, wherein the growth rate of Ni is 0.2A / s, and the growth rate of Au is 2A / s, and a Ni / Au gate electrode 6 is prepared by stripping.
[0066] In a nitrogen atmosphere, annealing is performed at a temperature of 800°C-900°C for 30-90 seconds, so that the source electrode 3 and the drain electrode 4 form an ohmic contact with the AlGaN / GaN heterojunction epitaxial layer 1, and the magnetron sputtered metal Ti or Ta reacts with nitrogen to generate a reactive metal layer; the excess reactive metal layer in the middle area on the upper surface of the source electrode 3 and the drain electrode 4 is removed by inductively coupled plasma etching technology to form an electrode contact wall 5.
[0067] Further, when the cap layer 2 is GaN, the reactive metal layer generated by the reaction of the magnetron sputtered metal Ti and nitrogen is TiN, forming the electrode contact wall 5, or the reactive metal layer generated by the magnetron sputtered metal Ta and nitrogen is TaN, forming the electrode contact wall 5;
[0068] When the cap layer 2 is SiN, the reaction metal layer formed by the magnetron sputtering of metal Ti, nitrogen and SiN is TiN / TiSi x The stacking forms the electrode contact wall 5, or the reaction metal layer formed by the reaction of the magnetron sputtered metal Ta with nitrogen and SiN is TaN / TaSi x The layers are stacked to form the electrode contact wall 5.
[0069] Embodiment 2:
[0070] The difference from Example 1 is that in this embodiment, the material of the cap layer 2 in step S1 is 2nm GaN; the metal deposited by magnetron sputtering in step S3 is 20nm Ta, and after annealing, the Ta deposited by magnetron sputtering reacts with nitrogen to generate TaN, forming electrode contact walls 5 on both sides of the source electrode 3 and the drain electrode 4.
[0071] Taking the GaN RF device with a self-aligned electrode contact wall structure prepared in Example 1 as an example, the device forms a self-aligned electrode contact wall structure by adopting a magnetron sputtering method. The DC output characteristic curve and the RF power output characteristic curve are as follows: Figure 6 and Figure 7 As shown. The output power and efficiency at low operating voltage are improved. The processes used in the examples are all mature processes for industrialized semiconductor production, and the preparation method is simple and does not require additional photolithography steps, realizing a self-aligned contact wall structure. The above-mentioned GaN RF device with a self-aligned electrode contact wall structure and the preparation method are suitable for large-scale production, and are used to improve the output power density and power added efficiency of the device at low operating voltage.
[0072] The above embodiments are only preferred examples of the present invention and do not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, they can make various modifications and changes in form and details according to the method of the present invention without departing from the principles and scope of the present invention. However, these modifications and changes based on the present invention are still within the scope of protection of the claims of the present invention.
Claims
1. A low-voltage GaN RF device with a self-aligned electrode contact wall structure, characterized in that: It comprises an AlGaN / GaN heterojunction epitaxial layer (1); The AlGaN / GaN heterojunction epitaxial layer (1) is a planar structure; A cap layer (2) is grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1), and a source electrode (3) and a drain electrode (4) are respectively arranged on both sides of the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1); Electrode contact walls (5) are provided on both sides of the source electrode (3) and the drain electrode (4) on the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1), and on both sides of the upper surface of the source electrode (3) and the drain electrode (4); A gate electrode (6) is provided on the upper surface of the cap layer (2).
2. The low-voltage GaN RF device with a self-aligned electrode contact wall structure according to claim 1, characterized in that: The gate electrode (6) comprises a Ni layer and an Au layer stacked from bottom to top; the gate electrode (6) is vertically arranged on the upper surface of the cap layer (2); the thicknesses of the Ni layer and the Au layer in the gate electrode (6) are 20-50nm and 200-400nm respectively; and the distance between the gate electrode (6) and the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1), i.e., the length, is 80-300nm.
3. The low-voltage GaN RF device with a self-aligned electrode contact wall structure according to claim 1, characterized in that: The thickness of the AlGaN / GaN heterojunction epitaxial layer (1) is 600-1000 μm, the cap layer (2) is GaN or SiN, and the thickness of the cap layer (2) is 2-5 nm.
4. The low-voltage GaN RF device with a self-aligned electrode contact wall structure according to claim 1, characterized in that: The source electrode (3) and the drain electrode (4) include a Ti layer, an Al layer, a Ni layer and an Au layer stacked in sequence from bottom to top; The thicknesses of the Ti layer, Al layer, Ni layer, and Au layer are 10-25 nm, 80-110 nm, 5-10 nm, and 80-110 nm, respectively; The distance between the source electrode (3) and the drain electrode (4) is 1-2 μm.
5. The low-voltage GaN RF device with a self-aligned electrode contact wall structure according to claim 1, characterized in that: The cap layer (2) comprises GaN or SiN; the length of the cap layer (2) is 2 nm.
6. The low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure according to claim 5, characterized in that: The electrode contact wall (5) includes TiN, TaN, TiN / TiSi x Stacked or TaN / TaSi x Lamination; If the cap layer (2) is GaN, the electrode contact wall (5) is a reactive metal layer TiN generated by the reaction of metal Ti and nitrogen generated by magnetron sputtering, or the electrode contact wall (5) is a reactive metal layer TaN generated by the reaction of metal Ta and nitrogen generated by magnetron sputtering; If the cap layer (2) is SiN, the electrode contact wall (5) is a reactive metal layer TiN / TiSi generated by the reaction of metal Ti, nitrogen and SiN by magnetron sputtering. x The stack, or electrode contact wall (5) is a reactive metal layer TaN / TaSi generated by magnetron sputtering of metal Ta and nitrogen and SiN x Overlay.
7. The low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure according to claim 1, characterized in that: The extended length of the electrode contact wall (5) on both sides of the source electrode (3) and the drain electrode (4), that is, the length of the contact portion of the electrode contact wall (5) with the upper surface of the cap layer (2) is 0.4-0.8 μm; The electrode contact walls (5) on both sides of the source electrode (3) and the drain electrode (4) are respectively arranged symmetrically with respect to the source electrode (3) and the drain electrode (4); the electrode contact walls (5) on both sides of the upper surfaces of the source electrode (3) and the drain electrode (4) are respectively arranged symmetrically with respect to the center of the upper surfaces of the source electrode (3) and the drain electrode (4); and the electrode contact walls (5) cover the upper surface and side surfaces of the source electrode (3) or the drain electrode (4).
8. A method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure, characterized in that: The following steps are involved: S1. Preparation and cleaning of an AlGaN / GaN heterojunction epitaxial layer (1): preparing an AlGaN / GaN heterojunction epitaxial layer (1) by metal organic vapor deposition (MOCVD), then immersing the AlGaN / GaN heterojunction epitaxial layer (1) in an acidic solution to remove a surface oxide layer, and then using an organic solvent to remove organic matter on the AlGaN / GaN heterojunction epitaxial layer (1); The cap layer (2) on the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1) is GaN or SiN grown at the center of the upper surface of the AlGaN / GaN heterojunction epitaxial layer (1) when the AlGaN / GaN heterojunction epitaxial layer (1) is grown by a metal organic compound chemical vapor deposition device, or SiN grown by a plasma enhanced chemical vapor deposition device after the AlGaN / GaN heterojunction epitaxial layer (1) is cleaned; S2, preparation of source and drain electrodes (3) and (4): defining the metal positions and patterns of the source electrode (3) and the drain electrode (4) by negative photolithography, and depositing the metal stack of the source electrode (3) and the drain electrode (4) by electron beam deposition; S3, preparation of electrode contact wall (5): Based on step S2, without stripping the source electrode (3) and the drain electrode (4) metal, Ti or Ta metal is continuously deposited on the position of the source electrode (3) and the drain electrode (4) metal stack by magnetron sputtering, and after stripping, annealing is performed in a nitrogen atmosphere to form a TiN / TiSi x Stacked or TaN / TaSi x The stacked reactive metal layer; removing the excess reactive metal layer in the middle region of the upper surface of the source electrode (3) and the drain electrode (4) by inductively coupled plasma etching technology to form an electrode contact wall (5); S4. Prepare the gate electrode (6) by a stripping process: use a photolithography machine to expose the gate electrode (6) pattern between the source electrode (3) and the drain electrode (4), and then deposit a gate electrode (6) material layer on the upper surface of the cap layer (2) between the source electrode (3) and the drain electrode (4) by electron beam evaporation, and prepare a Ni / Au gate electrode (6) by stripping.
9. The method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure according to claim 8, characterized in that: In step S3, the thickness of Ti or Ta metal deposited on the metal layer of the source electrode (3) and the drain electrode (4) by magnetron sputtering is 10-50 nm, and the length of the deposited Ti or Ta metal on the left and right sides of the source electrode (3) and the drain electrode (4) is 0.4-0.8 μm; Annealing is performed at a temperature of 800°C-900°C in a nitrogen atmosphere for a time range of 30-90 seconds, so that the source electrode (3) and the drain electrode (4) form an ohmic contact with the AlGaN / GaN heterojunction epitaxial layer (1), and the magnetron sputtered metal Ti or Ta reacts with nitrogen to generate a reactive metal layer; and the excess reactive metal layer in the middle area of the upper surface of the source electrode (3) and the drain electrode (4) is removed by inductively coupled plasma etching technology to form an electrode contact wall (5).
10. The method for preparing a low-voltage GaN radio frequency device with a self-aligned electrode contact wall structure according to claim 8, characterized in that: When the cap layer (2) is GaN, the reactive metal layer generated by the reaction of magnetron sputtered metal Ti and nitrogen is TiN, forming an electrode contact wall (5), or the reactive metal layer generated by the reaction of magnetron sputtered metal Ta and nitrogen is TaN, forming an electrode contact wall (5); When the cap layer (2) is SiN, the reaction metal layer formed by the reaction of magnetron sputtered metal Ti with nitrogen and SiN is TiN / TiSi x The stacking forms an electrode contact wall (5), or the reaction metal layer formed by the reaction of magnetron sputtered metal Ta with nitrogen and SiN is TaN / TaSi x The layers are stacked to form an electrode contact wall (5).