Gallium nitride bidirectional TVS device and method of manufacture

Abstract

This invention provides a gallium nitride bidirectional TVS device and its fabrication method. The device includes: a substrate; an insulating gallium nitride layer on the upper surface of the substrate; a first mesa structure, a second mesa structure, and a passivation layer on the upper surface of the insulating gallium nitride layer; the two mesa structures are, from bottom to top, a P- gallium nitride layer and a P+ gallium nitride layer, both embedded within the passivation layer; the lower surfaces of the two mesa structures are spaced apart by a predetermined distance; a first positive electrode is located on the upper surface of the first mesa structure, and a second positive electrode is located on the upper surface of the second mesa structure; the two positive electrodes are embedded within the passivation layer; and a first electrode hole is provided on the passivation layer at a position corresponding to the first positive electrode, and a second electrode hole is provided on the passivation layer at a position corresponding to the second positive electrode. This invention allows adjustment of the breakdown voltage of the gallium nitride bidirectional TVS device by adjusting the predetermined distance between the lower surfaces of the two mesa structures, thereby facilitating the operation of a low clamping voltage.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a gallium nitride bidirectional TVS device and its fabrication method. Background Technology

[0002] Transient voltage suppression (TVS) diodes have advantages such as fast response speed, large power absorption, low leakage current, and stable clamping voltage. These devices can clamp transient voltages and surges caused by lightning, system switching, electromagnetic pulses, and static electricity, thereby reducing the occurrence of burnout or breakdown of semiconductor devices in the whole machine and system, and thus ensuring the reliable operation of electronic circuits and precision components.

[0003] In existing technologies, the most commonly used high-efficiency transient voltage protection devices include unidirectional TVS devices and bidirectional TVS devices. A unidirectional TVS device typically includes a diode operating under an avalanche breakdown model, providing protection in one direction. A bidirectional TVS device is generally implemented using two back-to-back avalanche diodes, providing protection in both forward and reverse directions. Compared to unidirectional TVS devices, bidirectional TVS devices have a more complex structure, more stringent manufacturing requirements, and place greater demands on the properties of semiconductor materials. Currently, TVS diode devices are mainly implemented using silicon processes. However, the main problems with silicon-based bidirectional TVS diodes include: 1) low current, resulting in low power; 2) low voltage, limiting application range; 3) high series resistance, leading to thermal burnout. Therefore, the reliable operation of silicon-based bidirectional TVS diodes in electronic circuits and precision devices may not be guaranteed.

[0004] Therefore, gallium nitride (GaN), a third-generation wide-bandgap semiconductor material, possesses significant advantages in TVS device applications due to its high current density, low parasitic resistance, and low turn-on voltage. However, GaN diodes used in TVS devices need to operate in an avalanche breakdown model, but current research on GaN-based avalanche diodes is limited both domestically and internationally. The vertical structure is currently the dominant structure for TVS devices; however, for GaN, this structure is not conducive to achieving avalanche breakdown at lower breakdown voltages, thus hindering the reduction of the clamping voltage in bidirectional GaN TVS devices. Therefore, how to provide a bidirectional GaN TVS device capable of operating in an avalanche breakdown state at a lower breakdown voltage to clamp transient voltages and surges, thereby meeting the reliability requirements of electronic circuits and precision devices, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a gallium nitride bidirectional TVS device and its fabrication method to solve the problem that the structure of gallium nitride bidirectional TVS devices in the prior art is difficult to achieve a low clamping voltage.

[0006] In a first aspect, embodiments of the present invention provide a gallium nitride bidirectional TVS device, comprising:

[0007] Substrate;

[0008] An insulating gallium nitride layer located on the upper surface of the substrate;

[0009] A first mesa structure, a second mesa structure, and a passivation layer are located on the upper surface of the insulating gallium nitride layer; wherein the first mesa structure and the second mesa structure are embedded in the passivation layer; and the lower surface of the first mesa structure and the lower surface of the second mesa structure are spaced apart by a predetermined distance; and the first mesa structure and the second mesa structure are, from bottom to top, a P- gallium nitride layer and a P+ gallium nitride layer, respectively.

[0010] A first positive electrode is located on the upper surface of the first mezzanine structure, and a second positive electrode is located on the upper surface of the second mezzanine structure; wherein the first positive electrode and the second positive electrode are embedded in the passivation layer; and a first electrode hole is provided on the passivation layer at a position corresponding to the first positive electrode, and a second electrode hole is provided on the passivation layer at a position corresponding to the second positive electrode.

[0011] In one possible implementation, the preset distance is 10 nm to 10 μm.

[0012] In one possible implementation, the angle between the inner sidewall of the first mesa structure and the upper surface of the insulating gallium nitride layer, and the angle between the inner sidewall of the second mesa structure and the upper surface of the insulating gallium nitride layer, are in the range of 5° to 85°.

[0013] In one possible implementation, the first positive electrode and the second positive electrode are at least one of palladium-gold electrode, titanium-gold electrode and nickel-gold electrode.

[0014] In one possible implementation, the doping concentration of the insulating gallium nitride layer is less than 1e. 16 cm -3 .

[0015] In one possible implementation, the passivation layer is a silicon dioxide layer, a silicon nitride layer, or a quartz glass layer.

[0016] Secondly, embodiments of the present invention provide a method for fabricating a gallium nitride bidirectional TVS device, comprising:

[0017] Obtain a substrate, and sequentially prepare an insulating gallium nitride layer, a P- gallium nitride layer, and a P+ gallium nitride layer on the upper surface of the substrate;

[0018] The P+ gallium nitride layer and the P- gallium nitride layer are etched based on a mask layer with a preset pattern, forming a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer.

[0019] A first positive electrode is prepared on the upper surface of the P+ gallium nitride layer in the first mesa structure, and a second positive electrode is prepared on the upper surface of the P+ gallium nitride layer in the second mesa structure.

[0020] A passivation layer covering the first mesa structure, the second mesa structure, the first positive electrode, and the second positive electrode is prepared on the upper surface of the insulating gallium nitride layer. A first electrode hole is prepared on the upper surface of the passivation layer at the position corresponding to the first positive electrode, and a second electrode hole is prepared on the upper surface of the passivation layer at the position corresponding to the second positive electrode, thereby obtaining a gallium nitride bidirectional TVS device.

[0021] In one possible implementation, the mask layer based on a preset pattern etches the P+ gallium nitride layer and the P- gallium nitride layer to form a first mesa structure and a second mesa structure with their lower surfaces spaced at a preset distance on the upper surface of the insulating gallium nitride layer, including:

[0022] Based on a mask layer with a preset pattern, the P+ gallium nitride layer and the P- gallium nitride layer are etched to form a first mesa structure and a second mesa structure on the upper surface of the insulating gallium nitride layer with a preset distance between them and the inner sidewall of the mesa structure forming a preset angle with the upper surface of the insulating gallium nitride layer.

[0023] The preset included angle ranges from 5° to 85°.

[0024] In one possible implementation, the preset distance is 10 nm to 10 μm.

[0025] In one possible implementation, the mask layer is any one of photoresist, silicon dioxide, silicon nitride, or metal.

[0026] This invention provides a gallium nitride bidirectional TVS device and its fabrication method. The gallium nitride bidirectional TVS device includes: a substrate; an insulating gallium nitride layer on the upper surface of the substrate; a first mesa structure, a second mesa structure, and a passivation layer on the upper surface of the insulating gallium nitride layer; wherein the first mesa structure and the second mesa structure are embedded in the passivation layer; and the lower surface of the first mesa structure and the lower surface of the second mesa structure are spaced apart by a predetermined distance; and the first mesa structure and the second mesa structure are, from bottom to top, a P- gallium nitride layer and a P+ gallium nitride layer; a first positive electrode on the upper surface of the first mesa structure and a second positive electrode on the upper surface of the second mesa structure; wherein the first positive electrode and the second positive electrode are embedded in the passivation layer; and a first electrode hole is provided on the passivation layer at a position corresponding to the first positive electrode, and a second electrode hole is provided on the passivation layer at a position corresponding to the second positive electrode. In the structure of the gallium nitride bidirectional TVS device provided in this embodiment of the invention, a first positive electrode, a first mesa structure, and an insulating gallium nitride layer constitute a first diode, and a second positive electrode, a second mesa structure, and an insulating gallium nitride layer constitute a second diode. These two diodes share a common negative electrode on the insulating gallium nitride layer, thus forming a lateral gallium nitride bidirectional TVS device, which is beneficial for avalanche breakdown at a lower breakdown voltage. Furthermore, by adjusting the distance between the two diodes (i.e., adjusting the preset distance between the lower surfaces of the two mesa structures), the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted, resulting in a lower breakdown voltage and thus meeting the operating requirements for low clamping voltage. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the gallium nitride bidirectional TVS device provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of a gallium nitride bidirectional TVS device provided in another embodiment of the present invention;

[0030] Figure 3 This is a flowchart illustrating the fabrication method of the gallium nitride bidirectional TVS device provided in this embodiment of the invention.

[0031] Figure 4 This is a schematic diagram of the structure for preparing a gallium nitride layer according to an embodiment of the present invention;

[0032] Figure 5This is a schematic diagram of the preparation of the mesa structure provided in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the electrode fabrication structure provided in an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the equivalent circuit of the gallium nitride bidirectional TVS device provided in an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0036] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0037] The implementation of the present invention will be described in detail below with reference to the accompanying drawings:

[0038] Figure 1 This is a schematic diagram of the structure of a gallium nitride bidirectional TVS device provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the gallium nitride bidirectional TVS device includes:

[0039] Substrate 1. For example, the material of substrate 1 may include sapphire, silicon carbide, silicon, diamond, aluminum nitride or gallium nitride, etc., and this application does not limit it.

[0040] An insulating gallium nitride layer 2 is located on the upper surface of substrate 1.

[0041] A first mesa structure 3, a second mesa structure 4, and a passivation layer 5 are located on the upper surface of the insulating gallium nitride layer 2; wherein the first mesa structure 3 and the second mesa structure 4 are embedded in the passivation layer 5; and the lower surface of the first mesa structure 3 and the lower surface of the second mesa structure 4 are spaced apart by a predetermined distance W; and the first mesa structure 3 and the second mesa structure 4 are, from bottom to top, a P- gallium nitride layer 10 and a P+ gallium nitride layer 11.

[0042] A first positive electrode 6 is located on the upper surface of the first mesa structure 3 and a second positive electrode 7 is located on the upper surface of the second mesa structure 4; wherein the first positive electrode 6 and the second positive electrode 7 are embedded in the passivation layer 5; and a first electrode hole 8 is provided on the passivation layer 5 at the position corresponding to the first positive electrode 6, and a second electrode hole 9 is provided on the passivation layer 5 at the position corresponding to the second positive electrode 7.

[0043] In this embodiment, a first diode is formed based on a first positive electrode 6, a first mesa structure 3, and an insulating gallium nitride layer 2, and a second diode is formed based on a second positive electrode 7, a second mesa structure 4, and an insulating gallium nitride layer 2. These two diodes share a common negative electrode on the insulating gallium nitride layer 2, thereby forming a gallium nitride bidirectional TVS device with a lateral structure. Furthermore, the preset distance W between the lower surfaces of the first mesa structure 3 and the lower surfaces of the second mesa structure 4 significantly affects the breakdown voltage of the gallium nitride bidirectional TVS device. By adjusting the preset distance between the lower surfaces of the two mesa structures (i.e., the distance between the two diodes), the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted. A low breakdown voltage allows the device to meet the low clamping voltage requirement. Therefore, in the actual fabrication of the gallium nitride bidirectional TVS device, the length of the preset distance W can be adjusted to further regulate the breakdown voltage. A low breakdown voltage of the gallium nitride bidirectional TVS device meets its low clamping voltage requirement. For example, in this embodiment, the smaller the preset distance W, the lower the breakdown voltage of the gallium nitride bidirectional TVS device. Therefore, when actually fabricating a gallium nitride bidirectional TVS device, the length of the preset distance W can be reasonably set as needed. This application does not limit this.

[0044] In addition, a first positive electrode 6 is provided on the upper surface of the first mezzanine structure 3, and a second positive electrode 7 is provided on the upper surface of the second mezzanine structure 4. For example... Figure 1 As shown, both the first positive electrode 6 and the second positive electrode 7 are embedded within the passivation layer 5. More specifically, the first positive electrode 6 is located on the upper surface of the P+ gallium nitride layer 11 in the first mesa structure 3, and the second positive electrode 7 is located on the upper surface of the P+ gallium nitride layer 11 in the second mesa structure 4. Furthermore, a first electrode hole 8 is provided on the passivation layer 5 at a position corresponding to the first positive electrode 6, and a second electrode hole 9 is provided on the passivation layer 5 at a position corresponding to the second positive electrode 7, so as to facilitate the leading out of the first positive electrode 6 and the second positive electrode 7 of the gallium nitride bidirectional TVS device based on the first electrode hole 8 and the second electrode hole 9, respectively.

[0045] In one possible implementation, the preset distance can be 10 nm to 10 μm.

[0046] In this embodiment, as Figure 1As shown, the preset distance W can be 10 nm to 10 μm. Specifically, in this embodiment, the preset distance W has a significant impact on the breakdown voltage of the gallium nitride bidirectional TVS device. By adjusting the preset distance between the lower surfaces of the two mesa structures, the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted. Controlling the breakdown voltage of the device to be low allows it to meet the operating requirements of low clamping voltage. Furthermore, when the length of the preset distance W between the lower surfaces of the first mesa structure 3 and the second mesa structure 4 is controlled to be between 10 nm and 10 μm, the breakdown voltage of the gallium nitride bidirectional TVS device can be controlled within the range of 3V to 3000V, thereby facilitating the meeting of the low clamping voltage operating requirements of the gallium nitride bidirectional TVS device.

[0047] In one possible implementation, the angle between the inner wall of the first mesa structure and the upper surface of the insulating gallium nitride layer, and the angle between the inner wall of the second mesa structure and the upper surface of the insulating gallium nitride layer, are in the range of 5° to 85°.

[0048] In this embodiment, Figure 2 This is a schematic diagram of a gallium nitride bidirectional TVS device according to another embodiment of the present invention, please refer to it as well. Figure 1 and Figure 2 In the actual design and fabrication of gallium nitride bidirectional TVS devices, breakdown typically occurs at the insulating gallium nitride layer 2, such as... Figure 1 The diagram shows a gallium nitride bidirectional TVS device structure, with two mesa structures in the gallium nitride bidirectional TVS device ( Figure 1 The right angle formed between the inner wall of the platform (θ1=θ2=90°) and the upper surface of the insulating gallium nitride layer 2 will generate a spike electric field. The spike electric field may cause Zener breakdown of the device at the right angle, resulting in device damage. This will prevent the gallium nitride bidirectional TVS device from reaching the set avalanche breakdown voltage.

[0049] Based on this, in this embodiment, as Figure 2 As shown, the angle θ1 between the inner sidewall of the first mesa structure 3 and the upper surface of the insulating gallium nitride layer 2, and the angle θ2 between the inner sidewall of the second mesa structure 4 and the upper surface of the insulating gallium nitride layer 2 are both within the range of 5° to 85°. By adjusting the angle at the corner, the peak electric field caused by the right angle can be effectively reduced, and Zener breakdown of the device at the right angle can be suppressed, thereby effectively avoiding the problem of potential device damage. This is beneficial for the gallium nitride bidirectional TVS device to reach the set avalanche breakdown voltage.

[0050] In one possible implementation, the first positive electrode and the second positive electrode are at least one of a palladium-gold electrode, a titanium-gold electrode, and a nickel-gold electrode.

[0051] In this embodiment, as Figure 1 As shown, the first positive electrode 6 and the second positive electrode 7 can be at least one of palladium-gold electrode, titanium-gold electrode, and nickel-gold electrode. For example, taking palladium-gold electrodes as the first positive electrode 6 and the second positive electrode 7, in the actual design and fabrication of a gallium nitride bidirectional TVS device, the side of the palladium-gold electrode closest to the upper surface of the P+ gallium nitride layer 11 is made of palladium. The palladium-gold electrode corresponding to the first positive electrode 6 is electroplated and thickened to form the upper surface of the P+ gallium nitride layer 11 in the first mesa structure 3. Similarly, the palladium-gold electrode corresponding to the second positive electrode 7 is electroplated and thickened to form the upper surface of the P+ gallium nitride layer 11 in the second mesa structure 4. The thickness of these two electrodes, the first positive electrode 6 and the second positive electrode 7, can be between 100 nm and 10 μm.

[0052] In one possible implementation, the doping concentration of the insulating gallium nitride layer is less than 1e. 16 cm -3 .

[0053] In this embodiment, as Figure 1 As shown, the doping concentration of the insulating gallium nitride layer 2 is less than 1e. 16 cm -3 .

[0054] In one possible implementation, the passivation layer is a silicon dioxide layer, a silicon nitride layer, or a quartz glass layer.

[0055] In this embodiment, as Figure 1 As shown, the passivation layer 5 can be a silicon dioxide layer, a silicon nitride layer, or a quartz glass layer, and this application does not limit it.

[0056] This invention provides a gallium nitride bidirectional TVS device, comprising: a substrate; an insulating gallium nitride layer on the upper surface of the substrate; a first mesa structure, a second mesa structure, and a passivation layer on the upper surface of the insulating gallium nitride layer; wherein the first mesa structure and the second mesa structure are embedded in the passivation layer; and the lower surface of the first mesa structure and the lower surface of the second mesa structure are spaced apart by a predetermined distance; and the first mesa structure and the second mesa structure are, from bottom to top, a P- gallium nitride layer and a P+ gallium nitride layer; a first positive electrode on the upper surface of the first mesa structure and a second positive electrode on the upper surface of the second mesa structure; wherein the first positive electrode and the second positive electrode are embedded in the passivation layer; and a first electrode hole is provided on the passivation layer at a position corresponding to the first positive electrode, and a second electrode hole is provided on the passivation layer at a position corresponding to the second positive electrode. In the structure of the gallium nitride bidirectional TVS device provided in this embodiment of the invention, a first positive electrode, a first mesa structure, and an insulating gallium nitride layer constitute a first diode, and a second positive electrode, a second mesa structure, and an insulating gallium nitride layer constitute a second diode. These two diodes share a common negative electrode on the insulating gallium nitride layer, thus forming a lateral gallium nitride bidirectional TVS device, which is beneficial for avalanche breakdown at a lower breakdown voltage. Furthermore, by adjusting the distance between the two diodes (i.e., adjusting the preset distance between the lower surfaces of the two mesa structures), the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted, resulting in a lower breakdown voltage and thus meeting the operating requirements for low clamping voltage.

[0057] Figure 3 The flowchart illustrates the fabrication method of the gallium nitride bidirectional TVS device provided in this embodiment of the invention. Figure 3 As shown, this embodiment of the invention also provides a method for fabricating a gallium nitride bidirectional TVS device, comprising:

[0058] Step 301: Obtain a substrate, and sequentially prepare an insulating gallium nitride layer, a P- gallium nitride layer, and a P+ gallium nitride layer on the upper surface of the substrate.

[0059] In step 301, Figure 4 This is a schematic diagram of the structure for preparing a gallium nitride layer according to an embodiment of the present invention, as shown below. Figure 4 As shown. A substrate 1 is obtained, and an insulating gallium nitride layer 2, a P- gallium nitride layer 10, and a P+ gallium nitride layer 11 are sequentially fabricated on the upper surface of the substrate 1.

[0060] Step 302: Based on the mask layer with the preset pattern, etch the P+ gallium nitride layer and the P- gallium nitride layer to form a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer.

[0061] In step 302, Figure 5 This is a schematic diagram of the preparation of the mesa structure provided in an embodiment of the present invention, as shown below. Figure 5As shown, the P+ gallium nitride layer 11 and the P- gallium nitride layer 10 are sequentially etched based on the mask layer 12 with a preset pattern. The etching is terminated at the upper surface of the insulating gallium nitride layer 2 (or the insulating gallium nitride layer 2 of a preset thickness can be further etched before the etching is terminated). Then the mask layer 12 is removed, forming a pattern on the upper surface of the insulating gallium nitride layer 2 with a preset distance between the lower surface and the mask layer 11. Figure 5 The first tabletop structure 3 and the second tabletop structure 4 are shown. Specifically, the cross-sectional shapes of the first tabletop structure 3 and the second tabletop structure 4 can be as follows: Figure 5 The rectangle shown can also be as follows: Figure 2 The isosceles trapezoid shown is not limited in this application.

[0062] By controlling the length of the preset distance, the breakdown voltage of the gallium nitride bidirectional TVS device can be controlled and adjusted, thereby facilitating the low clamping voltage operation requirement of the gallium nitride bidirectional TVS device.

[0063] Step 303: Prepare a first positive electrode on the upper surface of the P+ gallium nitride layer in the first mesa structure, and prepare a second positive electrode on the upper surface of the P+ gallium nitride layer in the second mesa structure.

[0064] In step 303, Figure 6 This is a schematic diagram of the structure of the electrode provided in an embodiment of the present invention, as shown below. Figure 6 As shown, a first positive electrode 6 is prepared on the upper surface of the P+ gallium nitride layer 11 in the first mesa structure 3, and a second positive electrode 7 is prepared on the upper surface of the P+ gallium nitride layer 11 in the second mesa structure 4.

[0065] Step 304: A passivation layer covering the first mesa structure, the second mesa structure, the first positive electrode, and the second positive electrode is prepared on the upper surface of the insulating gallium nitride layer. A first electrode hole is prepared at the position corresponding to the first positive electrode on the upper surface of the passivation layer, and a second electrode hole is prepared at the position corresponding to the second positive electrode on the upper surface of the passivation layer, thereby obtaining a gallium nitride bidirectional TVS device.

[0066] In step 304, as Figure 1 As shown, a passivation layer 5 is prepared on the upper surface of the insulating gallium nitride layer 2, covering the first mesa structure 3, the second mesa structure 4, the first positive electrode 6, and the second positive electrode 7. A first electrode hole 8 is prepared on the upper surface of the passivation layer 5 at the position corresponding to the first positive electrode 6, and a second electrode hole 9 is prepared on the upper surface of the passivation layer 5 at the position corresponding to the second positive electrode 7. Thus, the first positive electrode 6 and the second positive electrode 7 of the gallium nitride bidirectional TVS device can be led out based on the first electrode hole 8 and the second electrode hole 9, respectively, thereby obtaining the gallium nitride bidirectional TVS device.

[0067] Figure 7 This is a schematic diagram of the equivalent circuit structure of the gallium nitride bidirectional TVS device provided in an embodiment of the present invention, as shown below. Figure 7 As shown, the gallium nitride bidirectional TVS device provided in this embodiment of the invention includes two diodes with a back-to-back structure in the circuit structure. The anodes of both diodes are fabricated on a P+ gallium nitride layer, that is... Figure 1 The first positive electrode 6 and the second positive electrode 7 are shown in the figure, and they share a common negative electrode on the insulating gallium nitride layer 2. This results in a gallium nitride bidirectional TVS device with a low turn-on voltage and low series resistance, leading to low power consumption. Furthermore, due to the high current density of gallium nitride, the bidirectional TVS device also has a high power tolerance. In this embodiment, the gallium nitride bidirectional TVS device with a lateral structure formed by two diodes is advantageous for avalanche breakdown at a lower breakdown voltage. Specifically, the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted by changing the spacing between the two diodes (i.e., the preset distance W between the lower surfaces of the first mesa structure 3 and the second mesa structure 4), thereby reducing the breakdown voltage and meeting the low clamping voltage requirement. Further, oblique etching is performed on the two mesa structures to obtain... Figure 2 When using the gallium nitride bidirectional TVS device shown, it can also effectively suppress Zener breakdown caused by peak electric fields, which is more conducive to enabling the gallium nitride bidirectional TVS device to reach the set avalanche breakdown voltage.

[0068] This invention provides a method for fabricating a gallium nitride bidirectional TVS device, comprising: obtaining a substrate and sequentially fabricating an insulating gallium nitride layer, a P- gallium nitride layer, and a P+ gallium nitride layer on the upper surface of the substrate; etching the P+ gallium nitride layer and the P- gallium nitride layer based on a mask layer with a preset pattern to form a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer; fabricating a first positive electrode on the upper surface of the P+ gallium nitride layer in the first mesa structure, and fabricating a second positive electrode on the upper surface of the P+ gallium nitride layer in the second mesa structure; fabricating a passivation layer covering the first mesa structure, the second mesa structure, the first positive electrode, and the second positive electrode on the upper surface of the insulating gallium nitride layer, and fabricating a first electrode hole at a position corresponding to the first positive electrode on the upper surface of the passivation layer, and fabricating a second electrode hole at a position corresponding to the second positive electrode on the upper surface of the passivation layer, thereby obtaining a gallium nitride bidirectional TVS device. The gallium nitride bidirectional TVS device fabricated using the method provided by this invention comprises a first positive electrode, a first mesa structure, and an insulating gallium nitride layer forming a first diode, and a second positive electrode, a second mesa structure, and an insulating gallium nitride layer forming a second diode. These two diodes share a common negative electrode on the insulating gallium nitride layer, thus forming a lateral gallium nitride bidirectional TVS device, which facilitates avalanche breakdown at a lower breakdown voltage. Furthermore, by adjusting the distance between the two diodes in the device (i.e., the preset distance between the lower surfaces of the two mesa structures), the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted, resulting in a lower breakdown voltage and thus meeting the requirement for low clamping voltage operation.

[0069] In one possible implementation, a P+ gallium nitride layer and a P- gallium nitride layer are etched based on a mask layer with a preset pattern, forming a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer, including:

[0070] Based on a mask layer with a preset pattern, P+ gallium nitride layer and P- gallium nitride layer are etched to form a first mesa structure and a second mesa structure on the upper surface of the insulating gallium nitride layer. The mesa structure has a preset distance between its inner sidewall and the upper surface of the insulating gallium nitride layer and forms a preset angle.

[0071] The preset included angle ranges from 5° to 85°.

[0072] In this embodiment, as Figure 5 As shown, the mask layer 12 based on the preset pattern sequentially etches the P+ gallium nitride layer 11 and the P- gallium nitride layer 10, terminating the etching at the upper surface of the insulating gallium nitride layer 2. Then, a pattern with a preset distance between the lower surface and the upper surface of the insulating gallium nitride layer 2 is formed on the upper surface of the insulating gallium nitride layer 2. Figure 5The first mesa structure 3 and the second mesa structure 4 are shown. Furthermore, the first mesa structure 3 and the second mesa structure 4 can be etched at an oblique angle to prepare the first mesa structure 3 and the second mesa structure 4 with a preset included angle of 5° to 85° between the inner sidewall of the mesa and the upper surface of the insulating gallium nitride layer 2.

[0073] In this embodiment, by adjusting the size of the preset included angle, the size of the peak electric field at the corner can be effectively improved, thereby avoiding the problem that a large peak electric field can easily cause Zener breakdown of the device, which would lead to device damage. This is beneficial for the gallium nitride bidirectional TVS device to reach the set avalanche breakdown voltage.

[0074] In one possible implementation, the mask layer is any one of photoresist, silicon dioxide, silicon nitride, or metal.

[0075] In this embodiment, as Figure 5 As shown, the mask layer 12 can be any one of photoresist, silicon dioxide, silicon nitride or metal, and this application does not limit it.

[0076] For example, when the mask layer 12 is photoresist, a first mesa structure 3 and a second mesa structure 4 with a preset included angle of 5° to 85° can be formed by photolithography of the inner sidewall of the mesa and the upper surface of the insulating gallium nitride layer 2 using a preset trapezoidal pattern of photoresist.

[0077] For example, when the mask layer 12 is any one of silicon dioxide, silicon nitride, or metal, the substrate 1, the insulating gallium nitride layer 2, the P- gallium nitride layer 10, and the P+ gallium nitride layer 11, which are arranged at an angle, can be etched by the mask layer 12 with a preset rectangular pattern to obtain a first mesa structure 3 and a second mesa structure 4 with a preset included angle of 5° to 85° between the inner sidewall of the mesa and the upper surface of the insulating gallium nitride layer 2.

[0078] In one possible implementation, the preset distance can be 10 nm to 10 μm.

[0079] In this embodiment, as Figure 1 As shown, the preset distance W can be 10 nm to 10 μm. Specifically, in this embodiment, the preset distance W has a significant impact on the breakdown voltage of the gallium nitride bidirectional TVS device. By adjusting the preset distance between the lower surfaces of the two mesa structures, the breakdown voltage of the gallium nitride bidirectional TVS device can be adjusted. Controlling the breakdown voltage of the device to be low allows it to meet the operating requirements of low clamping voltage. Furthermore, when the length of the preset distance W between the lower surfaces of the first mesa structure 3 and the second mesa structure 4 is controlled to be between 10 nm and 10 μm, the breakdown voltage of the gallium nitride bidirectional TVS device can be controlled within the range of 3V to 3000V, thereby facilitating the meeting of the low clamping voltage operating requirements of the gallium nitride bidirectional TVS device.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gallium nitride bidirectional TVS device, characterized in that, include: Substrate; An insulating gallium nitride layer located on the upper surface of the substrate; A first mesa structure, a second mesa structure, and a passivation layer are located on the upper surface of the insulating gallium nitride layer; wherein the first mesa structure and the second mesa structure are embedded in the passivation layer; and the lower surface of the first mesa structure and the lower surface of the second mesa structure are spaced apart by a predetermined distance; and the first mesa structure and the second mesa structure are, from bottom to top, a P- gallium nitride layer and a P+ gallium nitride layer, respectively. A first positive electrode is located on the upper surface of the first mezzanine structure, and a second positive electrode is located on the upper surface of the second mezzanine structure; wherein the first positive electrode and the second positive electrode are embedded in the passivation layer; and a first electrode hole is provided on the passivation layer at a position corresponding to the first positive electrode, and a second electrode hole is provided on the passivation layer at a position corresponding to the second positive electrode.

2. The gallium nitride bidirectional TVS device of claim 1, wherein, The preset distance is 10nm to 10μm.

3. The gallium nitride bidirectional TVS device of claim 1, wherein, The angle between the inner sidewall of the first platform structure and the upper surface of the insulating gallium nitride layer, and the angle between the inner sidewall of the second platform structure and the upper surface of the insulating gallium nitride layer, range from 5° to 85°.

4. The gallium nitride bidirectional TVS device of claim 1, wherein, The first positive electrode and the second positive electrode are at least one of palladium-gold electrode, titanium-gold electrode and nickel-gold electrode.

5. The gallium nitride bidirectional TVS device of claim 1, wherein, The doping concentration of the insulating gallium nitride layer is less than 1e. 16 cm -3 .

6. The gallium nitride bidirectional TVS device of claim 1, wherein, The passivation layer is a silicon dioxide layer, a silicon nitride layer, or a quartz glass layer.

7. A method for fabricating a gallium nitride bidirectional TVS device, characterized in that, include: Obtain a substrate, and sequentially prepare an insulating gallium nitride layer, a P- gallium nitride layer, and a P+ gallium nitride layer on the upper surface of the substrate; The P+ gallium nitride layer and the P- gallium nitride layer are etched based on a mask layer with a preset pattern, forming a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer. A first positive electrode is prepared on the upper surface of the P+ gallium nitride layer in the first mesa structure, and a second positive electrode is prepared on the upper surface of the P+ gallium nitride layer in the second mesa structure. A passivation layer covering the first mesa structure, the second mesa structure, the first positive electrode, and the second positive electrode is prepared on the upper surface of the insulating gallium nitride layer. A first electrode hole is prepared on the upper surface of the passivation layer at the position corresponding to the first positive electrode, and a second electrode hole is prepared on the upper surface of the passivation layer at the position corresponding to the second positive electrode, thereby obtaining a gallium nitride bidirectional TVS device.

8. The method of fabricating a gallium nitride bidirectional TVS device of claim 7, wherein, The mask layer based on a preset pattern etches the P+ gallium nitride layer and the P- gallium nitride layer, forming a first mesa structure and a second mesa structure with a preset distance between their lower surfaces on the upper surface of the insulating gallium nitride layer, including: Based on a mask layer with a preset pattern, the P+ gallium nitride layer and the P- gallium nitride layer are etched to form a first mesa structure and a second mesa structure on the upper surface of the insulating gallium nitride layer with a preset distance between them and the inner sidewall of the mesa structure forming a preset angle with the upper surface of the insulating gallium nitride layer. The preset included angle ranges from 5° to 85°.

9. The method of fabricating a gallium nitride bidirectional TVS device of claim 7, wherein, The preset distance is 10nm to 10μm.

10. The method for fabricating a gallium nitride bidirectional TVS device as described in claim 7, characterized in that, The mask layer is any one of photoresist, silicon dioxide, silicon nitride, or metal.

Images