阅读说明：本技术 阳极边缘浮空的GaN微波二极管及制备方法 (GaN microwave diode with floating anode edge and preparation method thereof ) 是由 张进成 党魁 周弘 张涛 张苇杭 宁静 郝跃 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种阳极边缘浮空的GaN微波二极管制备方法,主要解决GaN横向微波二极管电容大,频率响应慢的问题。自下而上包括衬底(1)、GaN缓冲层(2)、GaN沟道层(3)和AlGaN势垒层(4),该沟道层及势垒层上设有圆形凹槽(5),凹槽的外围势垒层上设有环形阴极(6),凹槽的底部、侧壁及凹槽边缘势垒层上方设有阳极(7),且凹槽边缘势垒层上方的阳极与下方势垒层之间设有80-300nm的间隙,形成长度为0.3-2μm的部分阳极浮空结构。本发明能大幅降低GaN微波二极管结电容,显著提高器件频率响应,可广泛应用于微波整流和微波限幅。(The invention discloses a preparation method of a GaN microwave diode with an empty anode edge, which mainly solves the problems of large capacitance and slow frequency response of a GaN transverse microwave diode. The GaN-based floating anode structure comprises a substrate (1), a GaN buffer layer (2), a GaN channel layer (3) and an AlGaN barrier layer (4) from bottom to top, wherein circular grooves (5) are formed in the channel layer and the barrier layer, annular cathodes (6) are arranged on the peripheral barrier layer of each groove, anodes (7) are arranged above the bottom, the side wall and the edge barrier layer of each groove, and a gap of 80-300nm is formed between each anode above the edge barrier layer of each groove and the barrier layer below the corresponding groove to form a partial anode floating structure with the length of 0.3-2 mu m. The invention can greatly reduce the junction capacitance of the GaN microwave diode, obviously improve the frequency response of the device, and can be widely applied to microwave rectification and microwave amplitude limiting.)

1. A GaN microwave diode with an anode edge floating structure comprises a substrate (1), a GaN buffer layer (2), a GaN channel layer (3) and an AlGaN barrier layer (4) from bottom to top, and is characterized in that circular grooves (5) are formed in the channel layer (3) and the barrier layer (4), annular cathodes (6) are arranged on the peripheral barrier layer of the grooves (5), anodes (7) are arranged on the bottoms and the side walls of the grooves (5) and above the groove edge barrier layer, and an 80-300nm gap is formed between the anode above the groove edge barrier layer and the barrier layer below the groove edge barrier layer, so that a partial anode floating structure with the length of 0.3-2 mu m is formed.

2. The diode of claim 1, wherein the depth of the recess (5) is 5-25nm below the AlGaN barrier and GaN surface.

3. The diode according to claim 1, characterized in that the substrate (1) is a SiC substrate with a thickness of 400 μm-600 μm or a sapphire substrate with a thickness of 400 μm-600 μm or a Si substrate with a thickness of 400 μm-1000 μm.

4. The diode according to claim 1, characterized in that the epitaxial buffer layer (2) is a GaN buffer layer with a thickness of 1 μm-6 μm or a AlGaN graded buffer layer with a thickness of 1 μm-6 μm.

5. A diode according to claim 1, characterized in that the GaN channel layer (3) is unintentionally doped GaN with a thickness of 100-400 nm.

6. Diode according to claim 1, characterised in that the anode (7) is a stack of Ni metal with a thickness of 30-200nm and Au metal with a thickness of 0-200 nm.

7. A preparation method of a GaN microwave diode with an empty anode edge is characterized by comprising the following steps:

1) cleaning an epitaxial wafer:

soaking an epitaxial wafer with an AlGaN/GaN structure in an HF acid solution or an HCl acid solution for 30s, sequentially placing the epitaxial wafer in an acetone solution, an absolute ethyl alcohol solution and deionized water, ultrasonically cleaning for 5min respectively, and then drying by using nitrogen;

2) manufacturing a GaN microwave diode cathode:

2a) sequentially carrying out glue homogenizing, glue drying, device cathode region photoetching and developing on a clean epitaxial wafer, and depositing a Ti/Al/Ni/Au metal lamination on the epitaxial wafer by using electron beam evaporation equipment;

2b) soaking an epitaxial wafer deposited with the Ti/Al/Ni/Au metal lamination layer in an acetone solution to strip metal in a photoresist area, then sequentially putting the epitaxial wafer into acetone, absolute ethyl alcohol and a deionized water solution to perform ultrasonic cleaning for 5 minutes respectively, blow-drying by nitrogen, and then putting the epitaxial wafer into a rapid annealing furnace to perform annealing to form a device cathode;

3) manufacturing a table top for isolation:

3a) carrying out glue homogenizing, glue drying mesa isolation photoetching and developing on the epitaxial wafer subjected to cathode ohmic contact;

3b) etching the area outside the GaN mesa by using an ICP etching machine;

3c) sequentially putting the etched epitaxial wafer into a clean acetone solution, an absolute ethyl alcohol solution and a deionized water solution for ultrasonic cleaning for 5 minutes respectively, and drying by using nitrogen to form device isolation;

4) depositing 80-300nm metal Ge on the epitaxial wafer with the mesa isolation by using electron beam evaporation equipment;

5) manufacturing an anode groove:

5a) sequentially carrying out glue homogenizing, glue drying, anode groove photoetching and developing on the epitaxial wafer deposited with the metal Ge;

5b) etching Ge metal in an anode open pore region of the epitaxial wafer to the surface of the barrier layer by using an RIE etching machine, etching the barrier layer and the channel layer to a position 5-25nm below an AlGaN/GaN interface by using an ICP etching machine, sequentially putting the barrier layer and the channel layer into solutions of acetone, absolute ethyl alcohol and deionized water, ultrasonically cleaning for 5 minutes respectively, drying by using nitrogen, and finishing the manufacture of an anode groove;

6) manufacturing an anode of the GaN microwave diode:

6a) sequentially carrying out glue homogenizing, glue drying, device anode area photoetching and developing on the epitaxial wafer etched with the anode groove, and depositing metal Ni with the thickness of 30-200nm and then depositing metal Au with the thickness of 0-200nm on the epitaxial wafer by using electron beam evaporation equipment;

6b) soaking the epitaxial wafer subjected to the operation of 6a) in an acetone solution to strip metal on a photoresist area, sequentially putting the epitaxial wafer into a clean acetone solution, an absolute ethyl alcohol solution and a deionized water solution, ultrasonically cleaning for 5 minutes respectively, and drying by using nitrogen to finish the manufacture of the anode of the diode;

7) ge metal wet etching:

putting the epitaxial wafer with the anode into H with the temperature of 40-80 DEG C₂O₂Soaking the solution for 3-5 minutes, taking out, washing with deionized water, and blow-drying with nitrogen to complete the manufacture of the GaN microwave diode with the floating anode edge.

8. The method of claim 7, wherein Ge metal is etched in 5b) under the following process conditions:

CF₄flow of gas：6-10sccm；

CHF₃Gas flow rate: 8-12 sccm;

flow rate of He gas: 120-;

radio frequency power: 150-300W;

reaction chamber pressure: 1000 and 2000 mTorr.

9. The method as claimed in claim 7, wherein the buffer layer and the barrier layer are etched in the step 5b), and the process conditions are as follows:

BCl₃gas flow rate: 20-40 sccm;

radio frequency power: 45-65W;

reaction chamber pressure: 15-25 mTorr.

Technical Field

The invention belongs to the technical field of microelectronics, and particularly relates to a GaN microwave diode with an anode with an edge floating, which can be used for microwave rectification or microwave amplitude limiting.

Technical Field

As a wide bandgap semiconductor material, a GaN material has great electrical performance advantages, an AlGaN/GaN heterojunction structure can induce high-concentration two-dimensional electron gas on one side of GaN near an interface due to strong spontaneous polarization and piezoelectric polarization effects, ionized impurity scattering and alloy disordered scattering are small due to the fact that electrons are contained in a potential well and impurity doping in the region is extremely small, and the two-dimensional electron gas has high mobility and electron saturation rate. And because of the inherent wide bandgap property of the material, the GaN has extremely high critical breakdown field intensity, and is suitable for manufacturing high-power high-frequency microwave devices. In order to further improve the frequency response of the GaN diode device, it is necessary to reduce the capacitance and resistance of the device.

Disclosure of Invention

The invention aims to overcome the defects of a GaN microwave diode, provides the GaN microwave diode based on anode edge floating and a preparation method thereof, and aims to reduce junction capacitance, improve device performance and greatly improve device working frequency by combining a groove anode etching process.

In order to realize the aim, the GaN microwave diode with the floating anode edge comprises a substrate, a GaN buffer layer, a GaN channel layer and an AlGaN barrier layer from bottom to top, and is characterized in that circular grooves are arranged on the channel layer and the barrier layer, an annular cathode is arranged on the peripheral barrier layer of each groove, anodes are arranged at the bottom and the side wall of each groove and above the barrier layer at the edge of each groove, and a gap of 80-300nm is arranged between the anode above the barrier layer at the edge of each groove and the barrier layer below the barrier layer to form a partial anode floating structure with the length of 0.3-2 mu m.

Preferably, the depth of the recess is 5 to 25nm below the AlGaN barrier and the GaN surface.

Preferably, the substrate is a SiC substrate having a thickness of 400 μm to 600 μm, a sapphire substrate having a thickness of 400 μm to 600 μm, or a Si substrate having a thickness of 400 μm to 1000 μm.

Preferably, the epitaxial buffer layer is a GaN buffer layer having a thickness of 1 μm to 6 μm or an AlGaN graded buffer layer having a thickness of 1 μm to 6 μm.

Preferably, the GaN channel layer is formed of unintentionally doped GaN having a thickness of 100nm to 400 nm.

Preferably, the anode is a stack of Ni metal with a thickness of 30-200nm and Au metal with a thickness of 0-200 nm.

In order to achieve the purpose, the invention discloses a method for preparing a GaN microwave diode with an anode with a floating edge, which has the technical key points that: evaporating 80nm-300nm metal Ge on a device with cathode ohmic contact and mesa isolation by electron beam, etching the Ge metal in an anode region by adopting an RIE (reactive ion etching) dry etching process, etching a barrier layer and a channel layer to 5-25nm below an AlGaN/GaN heterojunction interface by adopting an ICP (inductively coupled plasma) etching process, manufacturing an anode with Ni/Au metal, and then passing through H₂O₂The floating structure is realized by selectively etching the characteristics of Ge metal, so as to achieve the purpose of reducing the deviceThe purpose of junction capacitance. The method comprises the following specific steps:

1) cleaning an epitaxial wafer:

soaking an epitaxial wafer with an AlGaN/GaN structure in an HF acid solution or an HCl acid solution for 30s, sequentially placing the epitaxial wafer in an acetone solution, an absolute ethyl alcohol solution and deionized water, ultrasonically cleaning for 5min respectively, and then drying by using nitrogen;

2) manufacturing a GaN microwave diode cathode:

2a) sequentially carrying out glue homogenizing, glue drying, device cathode region photoetching and developing on a clean epitaxial wafer, and depositing a Ti/Al/Ni/Au metal lamination on the epitaxial wafer by using electron beam evaporation equipment;

2b) soaking an epitaxial wafer deposited with the Ti/Al/Ni/Au metal lamination layer in an acetone solution to strip metal in a photoresist area, then sequentially putting the epitaxial wafer into acetone, absolute ethyl alcohol and a deionized water solution to perform ultrasonic cleaning for 5 minutes respectively, blow-drying by nitrogen, and then putting the epitaxial wafer into a rapid annealing furnace to perform annealing to form a device cathode;

3) manufacturing a table top for isolation:

3a) carrying out glue homogenizing, glue drying mesa isolation photoetching and developing on the epitaxial wafer subjected to cathode ohmic contact;

3b) etching the area outside the GaN mesa by using an ICP etching machine;

3c) sequentially putting the etched epitaxial wafer into a clean acetone solution, an absolute ethyl alcohol solution and a deionized water solution for ultrasonic cleaning for 5 minutes respectively, and drying by using nitrogen to form device isolation;

4) depositing 80-300nm metal Ge on the epitaxial wafer with the mesa isolation by using electron beam evaporation equipment;

5) manufacturing an anode groove:

5a) sequentially carrying out glue homogenizing, glue drying, anode groove photoetching and developing on the epitaxial wafer deposited with the metal Ge;

5b) etching Ge metal in an anode open pore region of the epitaxial wafer to the surface of the barrier layer by using an RIE etching machine, etching the barrier layer and the channel layer to a position 5-25nm below an AlGaN/GaN interface by using an ICP etching machine, sequentially putting the barrier layer and the channel layer into solutions of acetone, absolute ethyl alcohol and deionized water, ultrasonically cleaning for 5 minutes respectively, drying by using nitrogen, and finishing the manufacture of an anode groove;

6) manufacturing an anode of the GaN microwave diode:

6a) sequentially carrying out glue homogenizing, glue drying, device anode area photoetching and developing on the epitaxial wafer etched with the anode groove, and depositing metal Ni with the thickness of 30-200nm and then depositing metal Au with the thickness of 0-200nm on the epitaxial wafer by using electron beam evaporation equipment;

6b) soaking the epitaxial wafer subjected to the operation of 6a) in an acetone solution to strip metal on a photoresist area, sequentially putting the epitaxial wafer into a clean acetone solution, an absolute ethyl alcohol solution and a deionized water solution, ultrasonically cleaning for 5 minutes respectively, and drying by using nitrogen to finish the manufacture of the anode of the diode;

7) ge metal wet etching:

putting the epitaxial wafer with the anode into H with the temperature of 40-80 DEG C₂O₂Soaking the solution for 3-5 minutes, taking out, washing with deionized water, and blow-drying with nitrogen to complete the fabrication of the GaN microwave diode with the floating anode edge.

The invention has the following advantages:

1. the invention adopts a groove anode structure, so that the Schottky metal is directly contacted with the side wall of the two-dimensional electron gas area, and the two-dimensional electron gas in the etching area is removed, therefore, the anode metal and the lower capacitor do not exist in the area, the junction capacitance of the device is greatly reduced, the anode of the device is allowed to be made into a larger circle, the manufacturing cost is reduced, and the yield is improved.

2. The invention utilizes heated H₂O₂The method has the characteristics that the solution reacts with Ge metal but does not react with Ni/Au, the Ge metal deposited between the edge of the anode of the device and the barrier layer is removed, the anode structure with the floating edge of the anode is realized, the capacitance introduced by the part of the anode is further reduced, the frequency characteristic of the device is greatly improved, and the method is simple, effective and high in operability.

Drawings

FIG. 1 is a schematic cross-sectional view of a conventional GaN lateral diode;

FIG. 2 is a schematic view of a cross-sectional structure of a conventional trench anode GaN lateral diode;

FIG. 3 is a schematic cross-sectional view of a GaN microwave diode with an empty anode edge according to the present invention;

fig. 4 is a schematic flow chart of the present invention for manufacturing the diode of fig. 3.

Detailed Description

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

Referring to fig. 3, the device of the invention is carried out on an AlGaN/GaN epitaxial wafer, which comprises a substrate 1, an epitaxial buffer layer 2, a GaN channel layer 3 and an AlGaN barrier layer 4 from bottom to top, wherein the substrate 1 adopts a SiC substrate with a thickness of 400 μm-600 μm or a sapphire substrate with a thickness of 400 μm-600 μm or a Si substrate with a thickness of 400 μm-1000 μm, the epitaxial buffer layer 2 adopts a GaN buffer layer with a thickness of 1 μm-6 μm or an AlGaN graded buffer layer with a thickness of 1 μm-6 μm, the GaN channel layer 3 adopts unintentional doped GaN with a thickness of 100nm-400nm, and the AlGaN barrier layer 4 has a thickness of 20-30 nm. Circular grooves 5 are arranged on the channel layer 3 and the barrier layer 4, the depth of each groove is 5-25nm below the interface of the AlGaN barrier layer and the GaN channel layer, an annular cathode 6 is arranged on the barrier layer on the periphery of the groove 5, an anode 7 is arranged above the barrier layer on the bottom, the side wall and the edge of the groove 5, and the anode 7 is formed by laminating Ni metal with the thickness of 30-200nm and Au metal with the thickness of 0-200 nm. The length of the anode above the barrier layer at the edge of the groove is 0.3-2 μm, and a gap of 80-300nm is arranged between the anode and the barrier layer below the groove to form a floating structure of a part of the anode.

Referring to fig. 4, the method for preparing a microwave diode with floating GaN at the anode edge of the invention provides the following three examples: