WO2020186700A1 - Schottky diode, and manufacturing method for same - Google Patents

Abstract

A Schottky diode, and a manufacturing method for the same. The Schottky diode comprises: a gallium oxide substrate (102); an epitaxial gallium oxide layer (103) located on the gallium oxide substrate (102), wherein a side of the epitaxial gallium oxide layer (103) away from the gallium oxide substrate (102) is provided with multiple trenches; multiple p-type material structures (105) located in the multiple trenches; a first electrode (104) covering the p-type material structures (105) and the epitaxial gallium oxide layer (103); and a second electrode (101) located at a side of the gallium oxide substrate (102) away from the epitaxial gallium oxide layer (103). A PN heterojunction structure is formed between the p-type material structures (105) and the epitaxial gallium oxide layer (103), so as to overcome technical difficulties and high costs in forming a p-type doped material from a gallium oxide material for manufacturing high-performance Schottky diodes. In addition, Schottky diodes manufactured by the invention have a low turn-on voltage and a high reverse breakdown voltage under a high voltage and a large current, thereby improving operational stability of the Schottky diodes.

Description

Schottky diode and preparation method thereof

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office with an application number of 201910209930.0 on March 19, 2019. The entire content of this application is incorporated into this application by reference.

Technical field

The embodiments of the present application relate to semiconductor technology, for example, to a Schottky diode and a manufacturing method thereof.

Background technique

Gallium oxide is a wide band gap semiconductor material. The band gap of β-Ga ₂ O ₃ is about 4.85 eV. Its critical breakdown electric field is as high as 8 MV/cm. It also has controllable n-type doping, radiation resistance, and high melting point. Suitable for making high-voltage power electronic devices. Its applications include power electronic devices, radio frequency electronic devices, ultraviolet detectors, gas sensors, etc., and have broad application prospects in solid-state lighting, communications, consumer electronics, as well as new energy vehicles, smart grids and other fields. Gallium oxide has better high voltage resistance characteristics than third-generation semiconductor materials such as silicon carbide. Its Baliga's figure merit (BFOM) is about 4 times higher than that of gallium nitride and 9 times higher than that of silicon carbide. The substrate can be processed in a melt, so it has broad application prospects and meets the national requirements for energy conservation and emission reduction, intelligent manufacturing, communication and information security.

The research on gallium oxide is still in its infancy. Although experiments show that the breakdown electric field test value of gallium oxide devices has exceeded the theoretical value of gallium nitride and silicon carbide, the electrical characteristics of gallium oxide devices under current process conditions are compared with other The third-generation semiconductor devices still have a certain gap. Due to the deep acceptor energy level of gallium oxide and the hole self-binding effect, it is difficult for traditional p-type acceptor elements to be doped into gallium oxide to form a p-type material, and the related technology uses gallium oxide material to achieve PN The knot is usually accompanied by high technical difficulty and high cost. This largely limits the use of gallium oxide materials to make Schottky diodes, that is, it is impossible to use gallium oxide materials to make high-performance Schottky diodes.

Summary of the invention

The following is an overview of the topics detailed in this article. This summary is not intended to limit the scope of protection of the claims.

The application provides a Schottky diode and a preparation method thereof, so as to realize a high-performance Schottky diode using gallium oxide material.

In the first aspect, an embodiment of the present application provides a Schottky diode, the Schottky diode includes: a gallium oxide substrate; a gallium oxide epitaxial layer on the gallium oxide substrate, wherein the gallium oxide The side of the epitaxial layer away from the gallium oxide substrate is provided with multiple trenches; multiple p-type material structures located in the multiple trenches; covering the p-type material structure and the gallium oxide epitaxial layer First electrode; a second electrode located on the side of the gallium oxide substrate away from the gallium oxide epitaxial layer.

In one embodiment, the p-type material structure adopts a p-type In _x Al _y Ga _z N single-layer structure, a p-type In _x Al _y Ga _z N multilayer overlap structure or a p-type silicon carbide; In the p-type In _x Al _y Ga _z N, X+Y+Z=1.

In one embodiment, the thickness of the p-type material structure ranges from 20 nanometers to 500 nanometers.

In one embodiment, the grooves are periodically arranged, and the grooves are strip-shaped grooves or annular grooves.

In an embodiment, the gallium oxide substrate is an α-Ga ₂ O ₃ substrate, a β-Ga ₂ O ₃ substrate, a γ-Ga ₂ O ₃ substrate, a δ-Ga ₂ O ₃ substrate, or ε-Ga ₂ O ₃ substrate.

In an embodiment, both the first electrode and the second electrode include at least one of Ni, Ti, Al, Au, TiN, W, Pt, Pd, Mo, and ITO.

In an embodiment, the first electrode includes a field plate structure.

In a second aspect, an embodiment of the present application also provides a method for manufacturing a Schottky diode. The method includes: providing a gallium oxide substrate including an epitaxial layer; forming a plurality of trenches on the gallium oxide epitaxial layer; A plurality of p-type material structures are formed in the plurality of trenches; a first electrode is formed on the gallium oxide epitaxial layer and the p-type material structure; on the side of the gallium oxide substrate away from the gallium oxide epitaxial layer The second electrode is formed.

In an embodiment, forming a plurality of p-type material structures in the plurality of trenches includes: growing a p-type material film on the epitaxial layer of gallium oxide, the p-type material film filling the plurality of trenches Groove; remove the p-type material film outside the plurality of groove structures.

In one embodiment, forming the first electrode on the epitaxial layer of gallium oxide and the p-type material structure includes: fabricating the first electrode on the epitaxial layer of gallium oxide and the p-type material structure by metal evaporation. Electrode; forming a second electrode on the side of the gallium oxide substrate away from the epitaxial layer of gallium oxide includes: fabricating the second electrode on the side of the gallium oxide substrate away from the epitaxial layer of gallium oxide by metal evaporation The second electrode.

After reading and understanding the drawings and detailed description, other aspects can be understood.

Description of the drawings

FIG. 1 is a schematic structural diagram of a Schottky diode provided by an embodiment of the application;

2 is a flowchart of a method for manufacturing a Schottky diode according to an embodiment of the application;

3-6 are schematic diagrams of the structure of the film formed by the manufacturing method of the Schottky diode provided by the embodiment of the application.

detailed description

The application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the example embodiments described here are only used to explain the application, but not to limit the application. In addition, it should be noted that, for ease of description, the drawings only show a part of the structure related to the present application instead of all of the structure.

Referring to FIG. 1, FIG. 1 is a schematic structural diagram of a Schottky diode provided by an embodiment of the application. The Schottky diode includes a gallium oxide substrate 102; a gallium oxide epitaxial layer 103 on the gallium oxide substrate 102, wherein, The gallium oxide epitaxial layer 103 is provided with multiple trenches on the side away from the gallium oxide substrate 102; the p-type material structure 105 located in the multiple trenches; the first electrode covering the p-type material structure 105 and the gallium oxide epitaxial layer 103 104; the second electrode 101 located on the side of the gallium oxide substrate 102 away from the gallium oxide epitaxial layer 103.

In one embodiment, the gallium oxide substrate 102 is n-type highly doped (n+) gallium oxide, and the gallium oxide epitaxial layer 103 is n-type lowly doped (n-); the second electrode 101 and the gallium oxide substrate 102 There may be an ohmic contact between the first electrode 104, the gallium oxide epitaxial layer 103 and the plurality of p-type material structures 105, and the p-type material structure 105 may be placed in the trench. Concentrating on the bottom of the trench improves the voltage division capability of the depletion region in other parts and effectively increases the reverse breakdown voltage of the Schottky diode. The majority carriers in the p-type material structure 105 are holes, and the majority carriers in the gallium oxide epitaxial layer 103 are electrons, and the majority carriers (holes) in the p-type material structure 105 are directed to the gallium oxide epitaxial layer. 103, and the majority carriers (electrons) in the gallium oxide epitaxial layer 103 move to the p-type material structure 105, and a hetero PN junction structure is formed between the p-type material structure 105 and the gallium oxide epitaxial layer 103; and the first electrode A Schottky junction structure is formed between 104 and the gallium oxide epitaxial layer 103; and because the manufacturing technology of the p-type material structure 105 is relatively low, it only needs to grow on the gallium oxide epitaxial layer 103, that is, the p-type material structure 105 The formation of the structure has lower technical difficulty and cost compared with the use of gallium oxide materials to form p-type semiconductor materials, thereby greatly reducing the difficulty and cost of using gallium oxide materials to form PN junctions; when the Schottky diode is working in the forward direction, When a small operating voltage is applied between the first electrode 104 and the second electrode 101, because the Schottky junction has a small turn-on voltage, the Schottky junction is turned on first. As the applied voltage increases, the heterogeneous PN The junction also begins to conduct, and the N-type material begins to inject a large amount of electrons into the drift region, thereby reducing the on-resistance in the drift region. That is, when the Schottky diode is working at a large current, its forward voltage is also lower. At the same time, after the PN junction is turned on, the pressure drop of the PN junction remains unchanged.

The technical solution of this embodiment adopts a Schottky diode including a gallium oxide substrate, a gallium oxide epitaxial layer, multiple p-type material structures, a first electrode and a second electrode, and the p-type material structure and the gallium oxide epitaxial layer Heterogeneous PN junction structure is formed between them, thereby avoiding the high technical difficulty and high cost that accompany the production of Schottky diodes due to the difficulty of forming p-type doped materials with gallium oxide materials. The diode has a lower turn-on voltage and a higher reverse breakdown voltage in the case of high voltage and large current, which improves the stability of the Schottky diode.

In one embodiment, the p-type material structure 105 adopts a p-type In _x Al _y Ga _z N single-layer structure, a p-type In _x Al _y Ga _z N multilayer overlap structure or a p-type silicon carbide; when the p-type material structure When 105 adopts a p-type In _x Al _y Ga _z N single-layer structure or a p-type In _x Al _y Ga _z N multilayer overlap structure, the p-type material structure 105 is doped with magnesium; when the p-type material structure 105 adopts In the case of p-type silicon carbide, the p-type material structure 105 is doped with aluminum.

It can be understood that when the p-type material structure 105 adopts a p-type In _x Al _y Ga _z N single-layer structure or a p-type In _x Al _y Ga _z N multilayer structure, the doped p-type material structure 105 The element may also be other elements except magnesium; when p-type silicon carbide is used in the p-type material structure 105, the element doped in the p-type material structure 105 may also be other elements other than aluminum.

In one embodiment, the thickness of the p-type material structure 105 ranges from 20 nanometers to 500 nanometers. If the p-type material structure 105 is too thin, it cannot provide effective holes, and if the p-type material structure 105 is too thick, it will introduce more material defects, increase the body resistance and capacitance, and affect the performance of the Schottky diode. performance. By controlling the thickness of the p-type material structure 105, the thickness of the depletion layer between the p-type material structure 105 and the gallium oxide epitaxial layer 103 can reach a better level, which further improves the performance of the Schottky diode, such as p-type The thickness of the material structure 105 may be 100 nanometers.

In one embodiment, the gallium oxide substrate 102 uses an α-Ga ₂ O ₃ substrate, a β-Ga ₂ O ₃ substrate, a γ-Ga ₂ O ₃ substrate, a δ-Ga ₂ O ₃ substrate, or ε -Ga ₂ O ₃ substrate.

Exemplarily, the β-Ga ₂ O ₃ substrate has high conductivity, low cost, and good chemical and thermal stability, and β-Ga ₂ O ₃ can be used as the substrate.

In an embodiment, both the first electrode 101 and the second electrode 104 include at least one of Ni, Ti, Al, Au, TiN, W, Pt, Pd, Mo, and ITO.

In an embodiment, the first electrode 101 and the second electrode 104 may be a metal or a compound, or may be a laminated structure composed of multiple metals or compounds to improve the conductivity of the first electrode 101 and the second electrode 104 performance.

In one embodiment, the first electrode 101 may include a field plate structure or a terminal protection structure. For example, a floating p-type guard ring may be used to improve the electric field distribution of the Schottky diode, so as to further improve the Schottky diode. The breakdown voltage of the base diode enhances the stability of the Schottky diode.

In an embodiment, the grooves are periodically arranged, and the grooves are strip-shaped grooves or annular grooves.

Exemplarily, the trench can be a bar-gate structure, or a concentric ring structure with equal intervals; by providing a periodic trench structure, the difficulty of manufacturing Schottky diodes can be reduced, and the Schottky diode can be further improved. The electric field distribution of the diode makes the electric field distribution in the Schottky diode more uniform and enhances the performance of the Schottky diode.

Referring to FIG. 2, FIG. 2 is a flow chart of a method for manufacturing a Schottky diode according to an embodiment of the application; FIGS. 3-6 are diagrams of a film formed by the method for manufacturing a Schottky diode according to an embodiment of the application. Schematic diagram of the structure; the preparation method of the Schottky diode includes step 201 to step 204.

Step 201, forming a plurality of trenches on the epitaxial layer of gallium oxide.

Exemplarily, a gallium oxide substrate including an epitaxial layer can be used, such as a gallium oxide substrate in the related art; if a substrate including a gallium oxide epitaxial layer is not used, a corresponding layer can be grown on the gallium oxide substrate first. For the epitaxial layer, step 201 is performed again.

Referring to Fig. 3, dry etching or wet etching can be used to prepare multiple trenches; since wet etching is generally used to make larger devices, and dry etching has good anisotropic etching properties, So as to ensure the fidelity of small graphics after transfer. For example, dry etching is used to produce multiple trenches, and the gas used in the dry etching is one or a mixture of SF ₆ , CF ₄ , BCl ₃ , Cl ₂ , and Ar ₂ .

Step 202, forming a plurality of p-type material structures in the plurality of trenches.

In an embodiment, referring to FIGS. 4 and 5, forming a plurality of p-type material structures 105 in a plurality of trenches includes: growing a p-type material film 301 on the epitaxial layer 103 of gallium oxide, and filling the p-type material film 301 with Multiple grooves.

Exemplarily, the growth method of the p-type material film 301 may be Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), and Hydride Vapor Phase Epitaxy (HVPE). ) Or Atom Layer Deposition (ALD). If the MOCVD method is used to grow p-type gallium nitride, the element doped in the p-type material film 301 can be magnesium, and the reaction source and carrier gas used for the growth of the p-type material film 301 are mainly trimethylgallium ( TMGa), trimethylaluminum (TMA), NH ₃ , Cp ₂ Mg, H ₂ , N ₂ and so on. The growth temperature of the p-type material film 301 is between 1000° C. and 1100° C., and magnesium cerene provides p-type dopants. If the MBE method is adopted, the nitrogen source is a nitrogen radio frequency nitrogen plasma source, solid gallium is used as a gallium source, solid magnesium is used as a magnesium source, the V/III ratio is 1/1, and the growth chamber pressure is 1.1×10 ^-4 mbar. It is understandable that the above-mentioned p-type material film 301 uses p-type aluminum indium gallium nitride as an example. If the p-type material film 301 uses p-type silicon carbide, hot wall CVD or LPCVD (Low Pressure Chemical Vapor Deposition, low-pressure chemical vapor deposition) is used to grow p-type silicon carbide, the reaction gas is pure silane and pure propane, the carrier gas is hydrogen, and the p-type dopant is trimethylaluminum.

The part of the p-type material film 301 outside the trench structure is removed.

Exemplarily, referring to FIG. 5, dry etching or chemical mechanical polishing (Chemical Mechanical Polishing, CMP) or laser lift-off may be used to remove the part of the p-type material film 301 located outside the trench structure, for example, the CMP method is used to expose The gallium oxide epitaxial layer 103 is formed, and a plurality of p-type material structures 105 are formed in the trench.

Step 203, forming a first electrode 104 on the epitaxial layer of gallium oxide and the p-type material structure.

In one embodiment, referring to FIG. 6, the first electrode 104 can be fabricated on the gallium oxide epitaxial layer 103 and the p-type material structure 105 by a metal evaporation method; the material of the first electrode 104 can be Ni, Ti, Al, One of Au, TiN, W, Pt, Pd, Mo and ITO, or a laminated structure composed of multiple. Evaporation methods include magnetron sputtering, electron beam evaporation, chemical plating and other programs. The metal of the first electrode 104 and the gallium oxide epitaxial layer 103 and the p-type material structure 105 form a Schottky contact structure.

Step 204, forming a second electrode 101 on a side of the gallium oxide substrate away from the epitaxial layer of gallium oxide.

In one embodiment, the second electrode 101 is made by metal evaporation on the side of the gallium oxide substrate 102 away from the gallium oxide epitaxial layer 103, and the material of the second electrode 101 can be Ni, Ti, Al, Au , TiN, W, Pt, Pd, Mo and ITO, or a laminated structure composed of multiple. Evaporation methods include magnetron sputtering, electron beam evaporation, chemical plating and other programs. Then, the metal of the second electrode 101 is thermally annealed using a high-temperature rapid annealing device, so that the metal of the first electrode 101 and the gallium oxide substrate 102 form an ohmic contact structure. Among them, the annealing temperature is generally 500 degrees to 900 degrees, and the annealing environment can be a nitrogen environment. It is understandable that the second electrode 101 can also be fabricated first, and then the first electrode 104 can be fabricated, which is not specifically limited in the embodiment of the present application.

The technical solution of this embodiment provides a method for preparing Schottky diodes to form a heterogeneous PN junction structure between the p-type material structure and the gallium oxide epitaxial layer, thereby avoiding the difficulty of forming the p-type material with the gallium oxide material. Doped materials are used to make Schottky diodes with high technical difficulty and high cost. At the same time, the manufactured Schottky diodes have a lower turn-on voltage under the condition of high voltage and large current, and have a higher reaction. The breakdown voltage improves the stability of the Schottky diode.

Claims (10)

1. A Schottky diode, the Schottky diode includes:

   Gallium oxide substrate;

   A gallium oxide epitaxial layer located on the gallium oxide substrate, wherein a plurality of trenches are provided on the gallium oxide epitaxial layer away from the gallium oxide substrate;

   A plurality of p-type material structures located in the plurality of trenches;

   A first electrode covering the p-type material structure and the gallium oxide epitaxial layer;

   A second electrode located on the side of the gallium oxide substrate away from the gallium oxide epitaxial layer.
2. The Schottky diode according to claim 1, wherein the p-type material structure adopts a p-type In _x Al _y Ga _z N single layer structure, a p-type In _x Al _y Ga _z N multilayer structure or a p Type silicon carbide;

   Wherein the p-type In _x Al _y Ga _z N in, X + Y + Z = 1 .
3. 4. The Schottky diode of claim 2, wherein the thickness of the p-type material structure ranges from 20 nanometers to 500 nanometers.
4. The Schottky diode according to claim 1, wherein the trenches are periodically arranged, and the trenches are strip-shaped trenches or annular trenches.
5. The Schottky diode according to claim 1, wherein the gallium oxide substrate is an α-Ga ₂ O ₃ substrate, a β-Ga ₂ O ₃ substrate, a γ-Ga ₂ O ₃ substrate, and a δ-Ga ₂ O ₃ substrate. Ga ₂ O ₃ substrate, or ε-Ga ₂ O ₃ substrate.
6. The Schottky diode according to claim 1, wherein the first electrode and the second electrode each comprise at least one of Ni, Ti, Al, Au, TiN, W, Pt, Pd, Mo, and ITO Kind.
7. The Schottky diode of claim 1, wherein the first electrode includes a field plate structure.
8. A preparation method of Schottky diodes includes:

   Provide a gallium oxide substrate including an epitaxial layer;

   Forming multiple trenches on the epitaxial layer of gallium oxide;

   Forming a plurality of p-type material structures in the plurality of trenches;

   Forming a first electrode on the epitaxial layer of gallium oxide and the p-type material structure;

   A second electrode is formed on the side of the gallium oxide substrate away from the epitaxial layer of gallium oxide.
9. 8. The method for manufacturing a Schottky diode according to claim 8, wherein forming a plurality of p-type material structures in the plurality of trenches comprises:

   Growing a p-type material film on the epitaxial layer of gallium oxide, the p-type material film filling the plurality of trenches;

   Removing the part of the p-type material film located outside the plurality of trench structures.
10. 8. The method for manufacturing a Schottky diode according to claim 8, wherein forming a first electrode on the epitaxial layer of gallium oxide and the p-type material structure comprises:

    Fabricating the first electrode by a metal evaporation method on the epitaxial layer of gallium oxide and the p-type material structure;

    Forming a second electrode on a side of the gallium oxide substrate away from the epitaxial layer of gallium oxide includes:

    The first electrode is fabricated on the side of the gallium oxide substrate away from the epitaxial layer of gallium oxide by a metal evaporation method.

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