Gallium nitride diode and manufacturing method thereof

Abstract

The invention discloses a gallium nitride diode and a manufacturing method thereof, and the gallium nitride diode comprises a gallium nitride substrate which comprises a first surface and a second surface which are opposite to each other; the gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate, and the gallium nitride epitaxial structure comprises a first gallium nitride transition layer, a gallium nitride intrinsic layer, a second gallium nitride transition layer and a gallium nitride contact layer which are sequentially stacked from bottom to top; wherein the gallium nitride epitaxial structure comprises an inclined mesa structure with a big lower part and a small upper part; the passivation layer is at least formed on the surface of the side wall of the inclined mesa structure; the first electrode is in contact with the gallium nitride substrate; and the second electrode is in contact with the gallium nitride contact layer. According to the gallium nitride diode and the manufacturing method thereof, electric field line gathering can be relieved, and the overall breakdown voltage of a device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a gallium nitride diode and a manufacturing method thereof. Background Art

[0002] Power electronic devices are widely used in all aspects of life, including autonomous driving, high-speed communications, switching power supplies, etc. As a third-generation semiconductor material, gallium nitride (GaN) has the advantages of large bandgap (much higher than silicon and silicon carbide), high thermal conductivity, high electron mobility and high breakdown field strength. Therefore, power electronic devices based on GaN often have better electrical performance than traditional Si-based devices.

[0003] However, most of the current commercial GaN power electronic devices are GaN lateral structure devices grown on foreign substrates, including silicon carbide (SiC), silicon (Si) and sapphire (Sapphire) substrates. Such lateral structure devices often require a larger area, and the use of foreign substrates also requires consideration of the adverse effects of factors such as lattice mismatch and thermal mismatch between different materials.

[0004] In recent years, a variety of GaN-based power electronic devices have developed rapidly, including high electron mobility transistors (HEMTS), Schottky diodes, PIN diodes, etc. GaN PIN diodes have excellent properties such as high breakdown voltage, low on-resistance, and short reverse recovery time, and are expected to be widely used.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a gallium nitride diode and a method for manufacturing the same, which can alleviate the concentration of electric field lines and improve the breakdown voltage of the entire device.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A gallium nitride diode, comprising:

[0009] A gallium nitride substrate having a first doping type, the gallium nitride substrate comprising a first surface and a second surface disposed opposite to each other;

[0010] A gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate, wherein the gallium nitride epitaxial structure comprises, from bottom to top, a first gallium nitride transition layer with a first doping type, a gallium nitride intrinsic layer with the first doping type, a second gallium nitride transition layer with a second doping type, and a gallium nitride contact layer with the second doping type, which are stacked in sequence;

[0011] Wherein, the gallium nitride epitaxial structure includes an inclined table structure with a larger bottom and a smaller top;

[0012] A passivation layer formed at least on the sidewall surface of the inclined mesa structure;

[0013] A first electrode in contact with the gallium nitride substrate; and

[0014] The second electrode is in contact with the gallium nitride contact layer.

[0015] In one or more embodiments of the present invention, the gallium nitride contact layer, the second gallium nitride transition layer, and the gallium nitride intrinsic layer together form an inclined mesa structure that is larger at the bottom and smaller at the top.

[0016] In one or more embodiments of the present invention, the tilt angle of the tilted table structure is 5°-10°.

[0017] In one or more embodiments of the present invention, the doping concentration of the gallium nitride substrate is in the range of 1e18 cm -3 -5e18cm -3 and / or,

[0018] The doping concentration range of the first gallium nitride transition layer is 1e18cm -3 -5e18cm -3 , with a thickness of 0.5 μm-1 μm; and / or,

[0019] The doping concentration of the gallium nitride contact layer is in the range of 5e19cm -3 -1e20cm -3 , thickness is 0.01μm-0.02μm.

[0020] In one or more embodiments of the present invention, the doping concentration of the GaN intrinsic layer is in the range of 2e15cm -3 -8e15cm -3 , thickness is 3μm-4μm;

[0021] The doping concentration range of the second gallium nitride transition layer is 3e18cm -3 -1e19cm -3 , thickness is 0.3μm-0.5μm.

[0022] In one or more embodiments of the present invention, the doping concentration of the GaN intrinsic layer is 2e15cm -3 , having a thickness of 3.5 μm; and / or,

[0023] The doping concentration of the second gallium nitride transition layer is in the range of 5e18cm -3 , thickness is 0.3μm.

[0024] In one or more embodiments of the present invention, the material of the second electrode includes Ni / Au; and / or,

[0025] The material of the first electrode includes Ti / Al / Ti / Au.

[0026] In one or more embodiments of the present invention, the first doping type is N-type, and the second doping type is P-type; or,

[0027] The first doping type is P type, and the second doping type is N type.

[0028] A method for manufacturing a gallium nitride diode, comprising:

[0029] Providing a gallium nitride substrate having a first doping type, the gallium nitride substrate comprising a first surface and a second surface disposed opposite to each other;

[0030] Growing a gallium nitride epitaxial structure on the first surface of the gallium nitride substrate, the gallium nitride epitaxial structure comprising, from bottom to top, a first gallium nitride transition layer with a first doping type, a gallium nitride intrinsic layer with the first doping type, a second gallium nitride transition layer with a second doping type, and a gallium nitride contact layer with the second doping type, which are stacked in sequence;

[0031] Etching the gallium nitride epitaxial structure to form an inclined mesa structure with a larger bottom and a smaller top;

[0032] forming a first electrode in contact with the gallium nitride substrate;

[0033] A passivation layer is formed at least on the sidewall surface of the inclined mesa structure and a second electrode is formed in contact with the gallium nitride contact layer.

[0034] In one or more embodiments of the present invention, etching the gallium nitride epitaxial structure to form an inclined mesa structure with a larger bottom and a smaller top includes:

[0035] forming a photoresist on the surface of the gallium nitride contact layer;

[0036] Performing high temperature baking on the photoresist to make the photoresist reflow and form an inclined angle;

[0037] Dry etching is performed to transfer the tilt angle of the photoresist to the GaN epitaxial structure to form a mesa structure with a tilted sidewall.

[0038] In one or more embodiments of the present invention, the doping concentration of the gallium nitride substrate is in the range of 1e18 cm -3 -5e18cm -3 and / or,

[0039] The doping concentration range of the first gallium nitride transition layer is 1e18cm -3 -5e18cm -3 , with a thickness of 0.5 μm-1 μm; and / or,

[0040] The doping concentration of the gallium nitride contact layer is in the range of 5e19cm -3 -1e20cm -3 , with a thickness of 0.01 μm-0.02 μm; and / or,

[0041] The doping concentration range of the GaN intrinsic layer is 2e15cm -3 -8e15cm -3 , with a thickness of 3 μm-4 μm; and / or,

[0042] The doping concentration range of the second gallium nitride transition layer is 3e18cm -3 -1e19cm -3 , thickness is 0.3μm-0.5μm.

[0043] Compared with the prior art, the gallium nitride diode and the manufacturing method thereof of the present invention use gallium nitride as a substrate to manufacture the gallium nitride diode, thereby avoiding the problems of lattice mismatch and thermal mismatch of the heterogeneous structure. In addition, the gallium nitride substrate has excellent thermal conductivity, which can greatly improve the stability and voltage resistance of the device as a whole, and can also reduce the overall area of ​​the device and increase space utilization.

[0044] The gallium nitride diode and the manufacturing method thereof of the present invention, by introducing the junction terminal extension technology, manufactures a device with an inclined table structure terminal, which can effectively alleviate the electric field line aggregation at the electrode edge, make the electric field distribution inside the device more uniform, and effectively improve the breakdown voltage of the device.

[0045] The gallium nitride diode and the manufacturing method thereof of the present invention prepare the inclined table structure terminal by a photoresist reflow method, which has simple process and low cost.

[0046] The gallium nitride diode and the manufacturing method thereof of the present invention further improve the breakdown voltage of the device by reducing the doping concentration of the gallium nitride intrinsic layer and regulating the doping concentration of the second gallium nitride transition layer, thereby greatly enhancing the reverse performance of the device and achieving avalanche breakdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 A schematic diagram of the structure of a gallium nitride diode in one embodiment of the present invention;

[0049] Figure 2 This is a process flow chart of a method for manufacturing a gallium nitride diode in one embodiment of the present invention;

[0050] Figure 3a-3f The present invention is a process structure diagram of a method for manufacturing a gallium nitride diode in one embodiment of the present invention;

[0051] Figure 4a The doping concentration of the second GaN transition layer is fixed at 1e19 cm-1 when the doping concentration of the second GaN transition layer is fixed at 1e19 cm-1 obtained by TCAD simulation in Example 1 of the present invention. -3 The doping concentration of the GaN intrinsic layer is 2e15cm -3 The electric field distribution diagram of the GaN diode during reverse breakdown;

[0052] Figure 4b The doping concentration of the second GaN transition layer is fixed at 1e19 cm-1 obtained by TCAD simulation in Example 1 of the present invention. -3 The doping concentration of the GaN intrinsic layer is 2e15cm -3 The breakdown curve of the GaN diode during reverse breakdown (voltage on the horizontal axis, current on the vertical axis);

[0053] Figure 5a The doping concentration of the second GaN transition layer is fixed at 1e19 cm-1 when the doping concentration of the second GaN transition layer is fixed at 1e19 cm-1. -3 The doping concentration of the GaN intrinsic layer is 2e16cm -3 The electric field distribution diagram of the GaN diode during reverse breakdown;

[0054] Figure 5b The doping concentration of the second GaN transition layer is fixed at 1e19 cm-1 when the doping concentration of the second GaN transition layer is fixed at 1e19 cm-1. -3 The doping concentration of the GaN intrinsic layer is 2e16cm -3 The breakdown curve of the GaN diode during reverse breakdown (voltage on the horizontal axis, current on the vertical axis);

[0055] Figure 6aThe doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 when the doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 obtained by TCAD simulation in Example 2 of the present invention. -3 The doping concentration of the second GaN transition layer is 5e18cm -3 The electric field distribution diagram of the GaN diode during reverse breakdown;

[0056] Figure 6b The doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 when the doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 obtained by TCAD simulation in Example 2 of the present invention. -3 The doping concentration of the second GaN transition layer is 5e18cm -3 Breakdown curve of the gallium nitride diode during reverse breakdown (voltage on the horizontal axis, current on the vertical axis).

[0057] Figure 7 The doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 when the doping concentration of the GaN intrinsic layer is fixed at 2e15 cm-1 in Comparative Example 2 of the present invention. -3 The doping concentration of the second GaN transition layer is 2e18cm -3 Electric field distribution diagram of the GaN diode during reverse breakdown. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0059] First, most of the current commercial GaN power electronic devices are GaN lateral structure devices grown on heterogeneous substrates, which leads to larger area, lattice mismatch and thermal mismatch. GaN self-supporting substrates can be used. GaN self-supporting substrates can be used to prepare devices with vertical structures. Without increasing the size of the device, vertical structure devices can obtain higher breakdown voltage and better heat dissipation performance, and will not be affected by lattice mismatch factors.

[0060] Secondly, the reverse breakdown voltage of existing GaN-based diodes often cannot reach the theoretical performance. Theoretically, the breakdown performance of GaN diodes when they are broken down under a strong electric field should be determined by the collision ionization of carriers in the internal active region, which eventually causes the device to avalanche breakdown. In practice, directly manufactured devices generally cannot achieve avalanche breakdown because there is electric field crowding inside the device, which reduces the device breakdown voltage.

[0061] When power electronic devices operate in a high-voltage blocking state, the edge effect of the device begins to appear. Unlike the relatively uniform electric field distribution inside the active area, the electric field lines at the edge of the device electrode are more densely distributed and the electric field is higher. When the local electric field exceeds the critical breakdown field strength of the semiconductor, the device will be partially broken down and damaged in advance, reducing the overall breakdown voltage and failing to achieve avalanche breakdown.

[0062] In order to solve this problem, it is necessary to introduce an edge terminal structure into the device. The terminal structure can alleviate the concentration of electric field lines, make the electric field more evenly distributed in the device, and improve the overall breakdown voltage. Currently, the widely used terminal structures include field plate structure, guard ring structure, junction terminal extension structure, mesa structure, etc.

[0063] The gallium nitride diode and the manufacturing method thereof of the present invention prepare a PIN diode on a gallium nitride substrate and manufacture a device with an inclined table structure terminal by introducing a junction terminal extension technology, thereby alleviating the concentration of electric field lines and improving the overall breakdown voltage of the device. Furthermore, by reducing the doping concentration of the gallium nitride intrinsic layer, the breakdown voltage of the device is further improved, thereby greatly enhancing the reverse performance of the device.

[0064] like Figure 1 As shown, a gallium nitride diode in an embodiment of the present invention includes a gallium nitride substrate 10 , a gallium nitride epitaxial structure 20 , a passivation layer 30 , a first electrode 40 and a second electrode 50 .

[0065] The gallium nitride substrate 10 has a first doping type with a doping concentration of 1e18 cm -3 -5e18cm -3 The gallium nitride substrate 10 includes a first surface and a second surface that are opposite to each other.

[0066] The gallium nitride epitaxial structure 20 is formed on the first surface of the gallium nitride substrate 10. The gallium nitride epitaxial structure 20 includes a first gallium nitride transition layer 21 with a first doping type, a gallium nitride intrinsic layer 22 with a first doping type, a second gallium nitride transition layer 23 with a second doping type, and a gallium nitride contact layer 24 with a second doping type, which are stacked in sequence from bottom to top. The gallium nitride epitaxial structure 20 includes an inclined mesa structure with a larger bottom and a smaller top. Specifically, the gallium nitride contact layer 24, the second gallium nitride transition layer 23, and the gallium nitride intrinsic layer 22 together form an inclined mesa structure with a larger bottom and a smaller top. The inclination angle of the inclined mesa structure is 5°-10°, preferably 6°.

[0067] The first doping type may be N-type, and the second doping type may be P-type; or the first doping type may be P-type, and the second doping type may be N-type.

[0068] In a preferred embodiment, the first GaN transition layer 21 is heavily N-type doped, with a doping concentration ranging from 1e18 cm -3 -5e18cm -3 , with a thickness of 0.5μm-1μm. The GaN intrinsic layer 22 is N-type lightly doped, with a doping concentration range of 2e15cm -3 -8e15cm -3 The second GaN transition layer 23 is P-type doped, the doping source is Mg, and the doping concentration range is 3e18cm -3 -1e19cm -3 The GaN contact layer 24 is heavily doped with P-type, the doping source is Mg, and the doping concentration range is 5e19cm -3 -1e20cm -3 , thickness is 0.01μm-0.02μm.

[0069] The passivation layer 30 is formed on the sidewall surface of the inclined mesa structure. The material of the passivation layer 30 is preferably SiO2, and the number of layers of the passivation layer 30 is at least two.

[0070] The first electrode 40 is formed on the second surface of the gallium nitride substrate 10 and contacts the gallium nitride substrate 10. The material of the first electrode 40 includes Ti / Al / Ti / Au.

[0071] The second electrode 50 is formed at the center of the inclined mesa structure and is located on the surface of the gallium nitride contact layer 24, and is disposed in contact with the gallium nitride contact layer 24. The material of the second electrode 50 includes Ni / Au.

[0072] like Figure 2 As shown, an embodiment of the present invention further provides a method for manufacturing the above-mentioned gallium nitride diode, which specifically includes the following steps:

[0073] S1, providing a gallium nitride substrate having a first doping type. The gallium nitride substrate comprises a first surface and a second surface arranged opposite to each other.

[0074] S2, growing a gallium nitride epitaxial structure on the first surface of the gallium nitride substrate. The gallium nitride epitaxial structure includes, from bottom to top, a first gallium nitride transition layer with a first doping type, a gallium nitride intrinsic layer with the first doping type, a second gallium nitride transition layer with a second doping type, and a gallium nitride contact layer with the second doping type, which are stacked in sequence.

[0075] The doping concentration of GaN substrate ranges from 1e18cm -3 -5e18cm -3 The doping concentration of the first GaN transition layer ranges from 1e18cm -3 -5e18cm -3, with a thickness of 0.5μm-1μm. The doping concentration of the GaN contact layer ranges from 5e19cm -3 -1e20cm -3 , with a thickness of 0.01μm-0.02μm. The doping concentration of the GaN intrinsic layer ranges from 2e15cm -3 -8e15cm -3 , with a thickness of 3μm-4μm. The doping concentration of the second GaN transition layer ranges from 3e18cm -3 -1e19cm -3 , thickness is 0.3μm-0.5μm.

[0076] S3, etching the GaN epitaxial structure to form an inclined mesa structure with a larger bottom and a smaller top.

[0077] Specifically, first, a photoresist is formed on the surface of the gallium nitride contact layer; secondly, the photoresist is baked at a high temperature to make the photoresist reflow and form a tilt angle; then, dry etching is performed to transfer the photoresist tilt angle to the gallium nitride epitaxial structure to form a mesa structure with inclined sidewalls; finally, the remaining photoresist is removed.

[0078] S4, forming a first electrode in contact with the gallium nitride substrate.

[0079] S5, forming a passivation layer at least on the sidewall surface of the inclined mesa structure and forming a second electrode in contact with the gallium nitride contact layer.

[0080] Specifically, a second electrode can be first formed on the surface of the gallium nitride contact layer, and then a passivation layer can be grown on the side wall surface and the upper surface of the inclined mesa structure as a whole. Then, the area where the second electrode is located is defined by photolithography, and finally a window is opened by wet etching to leak the second electrode.

[0081] Figure 3a-3f A process step diagram of a method for manufacturing a gallium nitride diode according to an embodiment of the present invention is shown. The method for manufacturing a gallium nitride diode according to the present invention will be described in detail below in conjunction with the accompanying drawings.

[0082] like Figure 3a As shown, an N-type gallium nitride substrate 10 is provided. The doping concentration of the gallium nitride substrate 10 is 1e18 cm -3 -5e18cm -3 The gallium nitride substrate 10 includes a first surface 10 a and a second surface 10 b that are opposite to each other.

[0083] like Figure 3b As shown, an N-type heavily doped first gallium nitride transition layer 21 is grown on the first surface 10a of the gallium nitride substrate 10 by MOCVD. The doping concentration of the first gallium nitride transition layer 21 is 1e18cm -3 -5e18cm -3The thickness is about 0.5 μm-1 μm. The N-type lightly doped GaN intrinsic layer 22 is grown on the N-type heavily doped first GaN transition layer 21 by MOCVD. The doping concentration of the GaN intrinsic layer 22 is in the range of 2e15 cm -3 -8e15cm -3 , with a thickness of 3μm-4μm. A P-type second GaN transition layer 23 is grown on the N-type lightly doped GaN intrinsic layer 22 by MOCVD. The doping source of the second GaN transition layer 23 is Mg, and the doping concentration range is 3e18cm -3 -1e19cm -3 , with a thickness of 0.3μm-0.5μm. A P-type heavily doped gallium nitride contact layer 24 is grown on the P-type second gallium nitride transition layer 23 by MOCVD to form a P-type ohmic contact with the electrode metal. The doping source of the gallium nitride contact layer 24 is Mg, and the doping concentration range is 5e19cm -3 -1e20cm -3 , thickness is 0.01μm-0.02μm.

[0084] like Figure 3c and Figure 3d As shown, the inclined mesa structure terminal is manufactured by photoresist reflow method.

[0085] For example, after photolithography development is performed on the surface of the gallium nitride contact layer 24 using AZ4620 photoresist, the photoresist 60 is baked at a high temperature to reflow and form a tilt angle, and then ICP etching is used to transfer the tilt angle of the photoresist to the gallium nitride epitaxial structure 20 to form a mesa structure with a tilted sidewall. After the etching is completed, the photoresist on the surface of the gallium nitride epitaxial structure 20 is removed, and the tilted mesa structure can be transferred to the gallium nitride epitaxial structure. This method can form a tilt angle of about 5°-10°.

[0086] like Figure 3e As shown, the second electrode region is defined on the surface of the gallium nitride contact layer 24 by photolithography, and the anode metal Ni / Au is plated on the gallium nitride contact layer 24 by electron beam evaporation. After cleaning and debonding, annealing is performed to form a P-type ohmic contact, and the second electrode 50 is prepared.

[0087] like Figure 3f As shown, a cathode electrode Ti / Al / Ti / Au is plated on the second surface 10 b of the gallium nitride substrate 10 by magnetron sputtering, and the first electrode 40 is prepared.

[0088] like Figure 1 As shown, a double-layer passivation layer 30 is grown on the anode metal of the second electrode 50 and the side wall surface of the inclined mesa structure using ALD+PECVD, and the second electrode area is defined by photolithography and then a window is opened by wet etching to expose the anode metal of the second electrode 50.

[0089] Embodiment 1:

[0090] A gallium nitride diode comprises a gallium nitride substrate, a gallium nitride epitaxial structure, a passivation layer, a first electrode and a second electrode.

[0091] The GaN substrate is an N-type substrate with a doping concentration of 1e18cm -3 The gallium nitride substrate includes a first surface and a second surface that are oppositely disposed.

[0092] The gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate. The gallium nitride epitaxial structure includes an N-type first gallium nitride transition layer, an N-type gallium nitride intrinsic layer, a P-type second gallium nitride transition layer and a P-type gallium nitride contact layer stacked in sequence from bottom to top. The gallium nitride contact layer, the second gallium nitride transition layer and the gallium nitride intrinsic layer together form an inclined mesa structure with a larger bottom and a smaller top. The inclined angle of the inclined mesa structure is 6°.

[0093] The doping concentration of the first GaN transition layer is 5e18cm -3 , with a thickness of 0.5 μm. The doping concentration of the GaN intrinsic layer is 2e15 cm -3 , with a thickness of 3.5 μm. The doping concentration of the second GaN transition layer is 1e19 cm -3 , with a thickness of 0.3 μm. The doping concentration of the GaN contact layer ranges from 1e20 cm -3 , thickness is 0.02μm.

[0094] The passivation layer is formed on the sidewall surface of the inclined mesa structure. The material of the passivation layer is preferably SiO2, and the number of layers of the passivation layer is two.

[0095] The first electrode is formed on the second surface of the gallium nitride substrate and is in contact with the gallium nitride substrate. The material of the first electrode is Ti / Al / Ti / Au.

[0096] The second electrode is formed at the center of the inclined mesa structure and is located on the surface of the gallium nitride contact layer, and is arranged in contact with the gallium nitride contact layer. The material of the second electrode is Ni / Au.

[0097] Comparative Example 1:

[0098] A gallium nitride diode comprises a gallium nitride substrate, a gallium nitride epitaxial structure, a passivation layer, a first electrode and a second electrode.

[0099] The GaN substrate is an N-type substrate with a doping concentration of 1e18cm -3 The gallium nitride substrate includes a first surface and a second surface that are oppositely disposed.

[0100] The gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate. The gallium nitride epitaxial structure includes an N-type first gallium nitride transition layer, an N-type gallium nitride intrinsic layer, a P-type second gallium nitride transition layer and a P-type gallium nitride contact layer stacked in sequence from bottom to top. The gallium nitride contact layer, the second gallium nitride transition layer and the gallium nitride intrinsic layer together form an inclined mesa structure with a larger bottom and a smaller top. The inclined angle of the inclined mesa structure is 6°.

[0101] The doping concentration of the first GaN transition layer is 5e18cm -3 , with a thickness of 0.5 μm. The doping concentration of the GaN intrinsic layer is 2e16 cm -3 , with a thickness of 3.5 μm. The doping concentration of the second GaN transition layer is 1e19 cm -3 , with a thickness of 0.3 μm. The doping concentration of the GaN contact layer ranges from 1e20 cm -3 , thickness is 0.02μm.

[0102] The passivation layer is formed on the sidewall surface of the inclined mesa structure. The material of the passivation layer is preferably SiO2, and the number of layers of the passivation layer is two.

[0103] The first electrode is formed on the second surface of the gallium nitride substrate and is in contact with the gallium nitride substrate. The material of the first electrode is Ti / Al / Ti / Au.

[0104] The second electrode is formed at the center of the inclined mesa structure and is located on the surface of the gallium nitride contact layer, and is arranged in contact with the gallium nitride contact layer. The material of the second electrode is Ni / Au.

[0105] Embodiment 2:

[0106] A gallium nitride diode comprises a gallium nitride substrate, a gallium nitride epitaxial structure, a passivation layer, a first electrode and a second electrode.

[0107] The GaN substrate is an N-type substrate with a doping concentration of 1e18cm -3 The gallium nitride substrate includes a first surface and a second surface that are oppositely disposed.

[0108] The gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate. The gallium nitride epitaxial structure includes an N-type first gallium nitride transition layer, an N-type gallium nitride intrinsic layer, a P-type second gallium nitride transition layer and a P-type gallium nitride contact layer stacked in sequence from bottom to top. The gallium nitride contact layer, the second gallium nitride transition layer and the gallium nitride intrinsic layer together form an inclined mesa structure with a larger bottom and a smaller top. The inclined angle of the inclined mesa structure is 6°.

[0109] The doping concentration of the first GaN transition layer is 5e18cm -3 , with a thickness of 0.5 μm. The doping concentration of the GaN intrinsic layer is 2e15 cm-3 , with a thickness of 3.5 μm. The doping concentration of the second GaN transition layer is 5e18 cm -3 , with a thickness of 0.3 μm. The doping concentration of the GaN contact layer ranges from 1e20 cm -3 , thickness is 0.02μm.

[0110] The passivation layer is formed on the sidewall surface of the inclined mesa structure. The material of the passivation layer is preferably SiO2, and the number of layers of the passivation layer is two.

[0111] The first electrode is formed on the second surface of the gallium nitride substrate and is in contact with the gallium nitride substrate. The material of the first electrode is Ti / Al / Ti / Au.

[0112] The second electrode is formed at the center of the inclined mesa structure and is located on the surface of the gallium nitride contact layer, and is arranged in contact with the gallium nitride contact layer. The material of the second electrode is Ni / Au.

[0113] Comparative Example 2:

[0114] A gallium nitride diode comprises a gallium nitride substrate, a gallium nitride epitaxial structure, a passivation layer, a first electrode and a second electrode.

[0115] The GaN substrate is an N-type substrate with a doping concentration of 1e18cm -3 The gallium nitride substrate includes a first surface and a second surface that are oppositely disposed.

[0116] The gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate. The gallium nitride epitaxial structure includes an N-type first gallium nitride transition layer, an N-type gallium nitride intrinsic layer, a P-type second gallium nitride transition layer and a P-type gallium nitride contact layer stacked in sequence from bottom to top. The gallium nitride contact layer, the second gallium nitride transition layer and the gallium nitride intrinsic layer together form an inclined mesa structure with a larger bottom and a smaller top. The inclined angle of the inclined mesa structure is 6°.

[0117] The doping concentration of the first GaN transition layer is 5e18cm -3 , with a thickness of 0.5 μm. The doping concentration of the GaN intrinsic layer is 2e15 cm -3 , with a thickness of 3.5 μm. The doping concentration of the second GaN transition layer is 2e18 cm -3 , with a thickness of 0.3 μm. The doping concentration of the GaN contact layer ranges from 1e20 cm -3 , thickness is 0.02μm.

[0118] The passivation layer is formed on the sidewall surface of the inclined mesa structure. The material of the passivation layer is preferably SiO2, and the number of layers of the passivation layer is two.

[0119] The first electrode is formed on the second surface of the gallium nitride substrate and is in contact with the gallium nitride substrate. The material of the first electrode is Ti / Al / Ti / Au.

[0120] The second electrode is formed at the center of the inclined mesa structure and is located on the surface of the gallium nitride contact layer, and is arranged in contact with the gallium nitride contact layer. The material of the second electrode is Ni / Au.

[0121] By changing the doping concentration of the GaN intrinsic layer and the second GaN transition layer of the GaN diode and comparing them, while keeping the doping concentration of other layers unchanged, it can be found that with the change of the doping concentration of the GaN intrinsic layer and the second GaN transition layer, the breakdown voltage of the GaN diode can be effectively improved. The doping concentration of the GaN intrinsic layer is 2e15cm -3 The doping concentration of the second GaN transition layer is 5e18cm -3 The GaN diode and the GaN intrinsic layer doping concentration are 2e16cm -3 The doping concentration of the second GaN transition layer is 1e19cm -3 Compared with the GaN diode, the breakdown voltage has been improved by about 200 V. On this basis, it is difficult to further reduce the doping concentration of the GaN intrinsic layer in terms of technology, and further reducing the doping concentration of the second GaN transition layer will cause the tilted mesa structure terminal to fail.

[0122] Figure 4a and Figure 4b 1 is an electric field distribution diagram and a breakdown curve of the gallium nitride diode of Example 1 during reverse breakdown. Figure 5a and Figure 5b The electric field distribution diagram and breakdown curve of the gallium nitride diode of comparative example 1 during reverse breakdown. Figure 6a and Figure 6b 1 and 2 are the electric field distribution diagram and breakdown curve of the gallium nitride diode of Example 2 during reverse breakdown. Figure 7 This is a diagram showing the electric field distribution of the gallium nitride diode of Example 3 during reverse breakdown.

[0123] pass Figure 4a , Figure 4b , Figure 5a , Figure 5b , Figure 6a , Figure 6b and Figure 7 It can be seen that by further adjusting the doping concentration of the second GaN transition layer, the doping concentrations of other layers remain unchanged. By increasing the Mg doping concentration of the second GaN transition layer from 1e19 cm -3 Reduced to 5e18cm -3 , which can further improve the breakdown voltage of the device and more effectively alleviate the electric field concentration effect. When the Mg doping concentration in the second GaN transition layer is reduced to 2e18cm -3When the peak electric field is transferred from the body to the outside, the terminal structure fails, which can be explained by the Mg doping concentration of the second GaN transition layer of 5e18cm -3 、GaN intrinsic layer doping concentration is 2e15cm -3 When the voltage is 0.04V, the GaN diode has the best performance and the highest breakdown voltage.

[0124] Compared with the prior art, the gallium nitride diode and the manufacturing method thereof of the present invention use gallium nitride as a substrate to manufacture the gallium nitride diode, thereby avoiding the problems of lattice mismatch and thermal mismatch of the heterogeneous structure. In addition, the gallium nitride substrate has excellent thermal conductivity, which can greatly improve the stability and voltage resistance of the device as a whole, and can also reduce the overall area of ​​the device and increase space utilization.

[0125] The gallium nitride diode and the manufacturing method thereof of the present invention, by introducing the junction terminal extension technology, manufactures a device with an inclined table structure terminal, which can effectively alleviate the electric field line aggregation at the electrode edge, make the electric field distribution inside the device more uniform, and effectively improve the breakdown voltage of the device.

[0126] The gallium nitride diode and the manufacturing method thereof of the present invention prepare the inclined table structure terminal by a photoresist reflow method, which has simple process and low cost.

[0127] The gallium nitride diode and the manufacturing method thereof of the present invention further improve the breakdown voltage of the device by reducing the doping concentration of the gallium nitride intrinsic layer and regulating the doping concentration of the second gallium nitride transition layer, thereby greatly enhancing the reverse performance of the device and achieving avalanche breakdown.

[0128] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0129] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A gallium nitride diode, characterized in that: include: A gallium nitride substrate having a first doping type, the gallium nitride substrate comprising a first surface and a second surface disposed opposite to each other; A gallium nitride epitaxial structure is formed on the first surface of the gallium nitride substrate, wherein the gallium nitride epitaxial structure comprises, from bottom to top, a first gallium nitride transition layer with a first doping type, a gallium nitride intrinsic layer with the first doping type, a second gallium nitride transition layer with a second doping type, and a gallium nitride contact layer with the second doping type, which are stacked in sequence; Wherein, the gallium nitride epitaxial structure includes an inclined table structure with a larger bottom and a smaller top; A passivation layer formed at least on the sidewall surface of the inclined mesa structure; A first electrode in contact with the gallium nitride substrate; and The second electrode is in contact with the gallium nitride contact layer.

2. The gallium nitride diode according to claim 1, characterized in that: The gallium nitride contact layer, the second gallium nitride transition layer and the gallium nitride intrinsic layer together form an inclined mesa structure which is larger at the bottom and smaller at the top.

3. The gallium nitride diode according to claim 2, characterized in that: The tilt angle of the tilted table structure is 5°-10°.

4. The gallium nitride diode according to claim 1, characterized in that: The doping concentration of the GaN substrate is in the range of 1e18 cm -3 -5e18cm -3 and / or, The doping concentration range of the first gallium nitride transition layer is 1e18cm -3 -5e18cm -3 , with a thickness of 0.5 μm-1 μm; and / or, The doping concentration of the gallium nitride contact layer is in the range of 5e19cm -3 -1e20cm -3 , with a thickness of 0.01 μm-0.02 μm; and / or, The doping concentration range of the GaN intrinsic layer is 2e15cm -3 -8e15cm -3 , with a thickness of 3 μm-4 μm; and / or, The doping concentration range of the second gallium nitride transition layer is 3e18cm -3 -1e19cm -3 , thickness is 0.3μm-0.5μm.

5. The gallium nitride diode according to claim 1, characterized in that: The doping concentration of the GaN intrinsic layer is 2e15cm -3 , having a thickness of 3.5 μm; and / or, The doping concentration range of the second gallium nitride transition layer is 5e18cm -3 , thickness is 0.3μm.

6. The gallium nitride diode according to claim 1, characterized in that: The material of the second electrode includes Ni / Au; and / or, The material of the first electrode includes Ti / Al / Ti / Au.

7. The gallium nitride diode according to claim 1, characterized in that: The first doping type is N-type, and the second doping type is P-type; or, The first doping type is P type, and the second doping type is N type.

8. A method for manufacturing a gallium nitride diode, characterized in that: include: Providing a gallium nitride substrate having a first doping type, the gallium nitride substrate comprising a first surface and a second surface disposed opposite to each other; Growing a gallium nitride epitaxial structure on the first surface of the gallium nitride substrate, the gallium nitride epitaxial structure comprising, from bottom to top, a first gallium nitride transition layer with a first doping type, a gallium nitride intrinsic layer with the first doping type, a second gallium nitride transition layer with a second doping type, and a gallium nitride contact layer with the second doping type, which are stacked in sequence; Etching the gallium nitride epitaxial structure to form an inclined mesa structure with a larger bottom and a smaller top; forming a first electrode in contact with the gallium nitride substrate; A passivation layer is formed at least on the sidewall surface of the inclined mesa structure and a second electrode is formed in contact with the gallium nitride contact layer.

9. The method for manufacturing a gallium nitride diode according to claim 8, characterized in that: Etching the GaN epitaxial structure to form an inclined mesa structure with a larger bottom and a smaller top, comprising: forming a photoresist on the surface of the gallium nitride contact layer; Performing high temperature baking on the photoresist to make the photoresist reflow and form an inclined angle; Dry etching is performed to transfer the tilt angle of the photoresist to the GaN epitaxial structure to form a mesa structure with a tilted sidewall.

10. The method for manufacturing a gallium nitride diode according to claim 8, characterized in that: The doping concentration of the GaN substrate is in the range of 1e18 cm -3 -5e18cm -3 and / or, The doping concentration range of the first gallium nitride transition layer is 1e18cm -3 -5e18cm -3 , with a thickness of 0.5 μm-1 μm; and / or, The doping concentration of the gallium nitride contact layer is in the range of 5e19cm -3 -1e20cm -3 , with a thickness of 0.01 μm-0.02 μm; and / or, The doping concentration range of the GaN intrinsic layer is 2e15cm -3 -8e15cm -3 , with a thickness of 3 μm-4 μm; and / or, The doping concentration range of the second gallium nitride transition layer is 3e18cm -3 -1e19cm -3 , thickness is 0.3μm-0.5μm.

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