A multi-stage trench self-protected schottky diode device and a manufacturing method thereof

Abstract

The application discloses a kind of multistage trench self-protecting schottky diode devices, comprising: gallium oxide substrate, gallium oxide epitaxial layer on the upper side of the gallium oxide substrate, the upper portion of the gallium oxide epitaxial layer is equipped with multistage trench, the multistage trench includes M≥2 level sub-trench, the opening distance of first level sub-trench to M level sub-trench successively reduces, the surface of the gallium oxide epitaxial layer and the bottom of the multistage trench are equipped with high resistance area, the surface of the multistage trench is deposited with schottky metal, the schottky metal forms schottky contact with the gallium oxide epitaxial layer, the schottky metal forms ohmic contact with the high resistance area.The schottky diode device of the application has low surface electric field, and the conductance modulation effect is fast, and gallium oxide SBD device with high voltage, large current, high reliability can be made.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a multi-level trench self-protected Schottky diode device unit structure and its fabrication method. Background Technology

[0002] Among wide-bandgap semiconductor materials, Ga₂O₃ possesses a bandgap of 4.8 eV, an ideal breakdown electric field strength of 8 MV / cm, and a BFOM value as high as 3400, approximately four times that of GaN and ten times that of SiC. Therefore, in today's power electronics applications demanding higher power density and lower power consumption, Ga₂O₃ material holds significant research importance and has a broader market application prospect. In contrast to the ease of n-type doping, there are currently no reports of successful p-type doping in Ga₂O₃, which limits its application in bipolar power devices compared to materials capable of bipolar doping. Because gallium oxide lacks effective p-type semiconductors, it cannot be fabricated into Schottky diodes with conventional bulk implantation or epitaxial p-type semiconductors like SiC and GaN. Currently, to reduce the reverse leakage current of Ga₂O₃ Schottky diodes, the devices can only be fabricated with fin structures, utilizing the characteristics of the field plate to disperse the electric field at the Schottky interface, distributing the electric field along the field plate. When the device operates in forward conduction, the current first flows along the fin epitaxial layer and then into the bulk, finally reaching the cathode. Although this structure can achieve a certain withstand voltage and forward conduction, it has significant drawbacks. First, it places high demands on the quality and thickness of the insulating dielectric of the field plate. Poor-quality dielectric and inappropriate thickness can lead to excessive electric field at certain points on the field plate and cause reliability failure. Second, during forward conduction, due to the limited width of the fin, the current conduction path cannot be extended when the current passes through the fin epitaxial layer, thus increasing the on-resistance. Finally, because the device cannot be conductivity modulated, it is prone to failure under high surge current, limiting its application in power circuits. Therefore, further development of Schottky diodes with low on-resistance, high withstand voltage, and strong surge resistance is needed.

[0003] To reduce on-resistance, lower the electric field at the metal-semiconductor interface, and improve surge resistance, a p-type oxide barrier layer such as NiO was introduced onto a Ga2O3 epitaxial layer to fabricate a planar heterojunction Schottky diode (JBS). Studies have shown that the heterojunction barrier can effectively shield part of the electric field, thereby improving the device's voltage capability. The planar Schottky diode has a wider conduction path, resulting in lower on-resistance. The heterojunction can turn on under a certain forward voltage, thus exhibiting a conductance modulation effect and surge resistance. However, because the p-type oxide barrier layer on the gallium oxide epitaxial surface does not sufficiently extend the depletion region under reverse blocking conditions, the electric field shielding ability is limited. The electric field at the metal-semiconductor interface remains strong, and leakage current increases significantly with increasing reverse voltage, severely affecting the stability of the Schottky contact and significantly impacting the long-term reliability of the device. Furthermore, during forward conduction, the heterojunction has a relatively large turn-on voltage, and the conductivity modulation effect is usually slow, increasing the risk of device failure. On the other hand, the crystal plane usually selected for Ga2O3 vertical devices is (001), while the crystal plane with the maximum carrier mobility of Ga2O3 is (010). Therefore, planar devices cannot take advantage of the characteristics of the optimal crystal plane. Summary of the Invention

[0004] To address the shortcomings of existing gallium oxide planar heterojunction barrier Schottky diodes (SBDs), such as a large surface electric field during reverse bias, slow conduction modulation during forward conduction, and inability to fully utilize the optimal surface characteristics of Ga2O3, this invention aims to provide a novel gallium oxide Schottky diode device unit structure with low surface electric field, fast conduction modulation effect, and utilization of the optimal Ga2O3 surface, in order to fabricate gallium oxide SBD devices with high voltage withstand capability, high current, and high reliability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] This invention provides a multi-level trench self-protected Schottky diode device, comprising: a gallium oxide substrate, a gallium oxide epitaxial layer located on the upper side of the gallium oxide substrate, a multi-level trench provided on the upper part of the gallium oxide epitaxial layer, the multi-level trench including M≥2 sub-trenches, the opening distance of the first sub-trench to the Mth sub-trench decreasing sequentially, a high-resistivity region provided on the surface of the gallium oxide epitaxial layer and the bottom of the multi-level trench, a Schottky metal deposited on the surface of the multi-level trench, the Schottky metal forming a Schottky contact with the gallium oxide epitaxial layer, and the Schottky metal forming an ohmic contact with the high-resistivity region.

[0007] Furthermore, the high-resistivity region is formed by P-type oxide deposition.

[0008] Furthermore, the p-type oxide is one of NiO and Cu2O.

[0009] Furthermore, the high-resistivity region is formed by ion implantation of the gallium oxide epitaxial layer at the bottom of the multi-level trench.

[0010] Furthermore, the element implanted by the ions is either N or Mg.

[0011] Furthermore, the Schottky contact portion is located on the sidewall of the multi-level trench and partially at the bottom of the multi-level trench.

[0012] Furthermore, the high-resistivity region is partly formed by P-type oxide deposition and partly formed by ion implantation of the gallium oxide epitaxial layer at the bottom of the multi-level trench.

[0013] Furthermore, a cathode metal is deposited on the bottom side of the gallium oxide substrate.

[0014] Furthermore, a passivation layer formed by an insulating medium is deposited on the surface of the Schottky metal.

[0015] The present invention also provides a method for fabricating the above-mentioned multi-level trench self-protected Schottky diode device, comprising the following steps:

[0016] The gallium oxide epitaxial layer is etched to form a multi-level trench including M-level sub-trenches;

[0017] A high-resistivity region is formed on the surface of the gallium oxide epitaxial layer and at the bottom of the multi-level trench;

[0018] Schottky metal is deposited on the surface of the multi-level trenches to form a Schottky contact with the gallium oxide epitaxial layer and an ohmic contact with the high-resistivity region.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The epitaxial layer of this invention adopts a multi-level trench structure, and a high-resistivity region is set at the bottom of the trench and the surface of the epitaxial layer to form a heterojunction with the epitaxial layer. The heterojunction barrier formed can shield the reverse electric field and reduce the leakage current of the device. When the device is forward-biased, multiple sidewall diodes can conduct simultaneously, reducing the on-resistance. The current mainly flows through the sidewalls. In practice, the crystal orientation with the highest mobility is selected

[010] , which is beneficial to reducing the on-resistance of the device. The current flows through the high-resistance region below the trench, where a potential difference is formed with the surface electrode, which is beneficial to the early turn-on of the heterojunction, improves the surge resistance of the device, and enhances the conductivity modulation effect. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the multi-level trench self-protected Schottky diode device structure in Example 1;

[0022] Figure 2 This is a schematic diagram of the fabrication process of the multi-level trench self-protected Schottky diode device in Example 1;

[0023] Figure 3 This is a schematic diagram of the current conduction of the multi-level trench self-protected Schottky diode device in Example 1;

[0024] Figure 4 This is a schematic diagram of the multi-level trench self-protected Schottky diode device structure in Example 2;

[0025] Figure 5 This is a schematic diagram of the multi-level trench self-protected Schottky diode device structure in Example 3. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; unless specifically specified, the technical means used are all conventional means well known to those skilled in the art.

[0027] This invention provides a multi-level trench self-protected Schottky diode device, comprising: a gallium oxide substrate, a gallium oxide epitaxial layer located on the upper side of the gallium oxide substrate, a multi-level trench provided on the upper part of the gallium oxide epitaxial layer, the multi-level trench including M≥2 sub-trenches, the opening distance of the first sub-trench to the Mth sub-trench decreasing sequentially, a high-resistivity region provided on the surface of the gallium oxide epitaxial layer and the bottom of the multi-level trench, a Schottky metal deposited on the surface of the multi-level trench, the Schottky metal forming a Schottky contact with the gallium oxide epitaxial layer and an ohmic contact with the high-resistivity region.

[0028] In some embodiments, the high-resistivity region is formed by P-type oxide deposition.

[0029] In some embodiments, the p-type oxide is one of NiO and Cu2O.

[0030] In some implementations, the high-resistivity region is formed by ion implantation of the gallium oxide epitaxial layer at the bottom of a multi-level trench.

[0031] In some implementations, the ion implanted element is one of N or Mg.

[0032] In some implementations, the Schottky contact portion is located on the sidewall of the multi-level trench and partly at the bottom of the multi-level trench.

[0033] In some implementations, the high-resistivity region is partially formed by P-type oxide deposition and partially formed by ion implantation of a gallium oxide epitaxial layer at the bottom of a multi-level trench.

[0034] In some embodiments, a cathode metal is deposited on the bottom side of the gallium oxide substrate.

[0035] In some embodiments, a passivation layer formed by an insulating medium is deposited on the surface of the Schottky metal, the insulating medium being selected from SiO2, Si3N4, etc.

[0036] This invention also provides a method for fabricating the above-mentioned multi-level trench self-protected Schottky diode device, comprising the following steps:

[0037] Etching the gallium oxide epitaxial layer forms a multi-level trench including M-level sub-trenches;

[0038] A high-resistivity region is formed on the surface of the gallium oxide epitaxial layer and at the bottom of the multi-level trench;

[0039] Schottky metal is deposited on the surface of the multi-level trench, forming a Schottky contact with the gallium oxide epitaxial layer and an ohmic contact with the high-resistivity region.

[0040] Example 1

[0041] This embodiment provides a multi-level trench self-protected Schottky diode device structure, as follows: Figure 1 As shown, a cathode 3 is deposited on the bottom side of a gallium oxide substrate 1, and a gallium oxide epitaxial layer 2 is deposited on the top side of the gallium oxide substrate 1. A secondary trench is provided on the upper part of the gallium oxide epitaxial layer 2, and the opening distance of the first sub-trench is greater than that of the second sub-trench. A P-type NiO layer 4 is deposited on the surface of the gallium oxide epitaxial layer 2 and at the bottom of the first and second sub-trenches. A metallic Ni layer 5 is deposited on the entire epitaxial layer and the surface of the secondary trench. The metallic Ni layer 5 forms a Schottky contact with the gallium oxide epitaxial layer 2 on the trench sidewall to form a Schottky diode, and forms an ohmic contact with the P-type NiO layer 4. A SiO2 passivation layer 6 filling the secondary trench is deposited on the surface of the metallic Ni layer 5.

[0042] The specific fabrication process of the multi-level trench self-protected Schottky diode device provided in this embodiment is as follows: Figure 2 As shown, firstly, cathode metal Ti / Au is deposited on the bottom side of the gallium oxide substrate 1, including the gallium oxide epitaxial layer 2, to create a back-side ohmic contact and form the device cathode 3; then, the gallium oxide epitaxial layer 2 is etched to form a secondary trench; P-type NiO is deposited and patterned on the surface of the gallium oxide epitaxial layer 2 and in the secondary trench, and the oxide on the trench sidewalls is removed, leaving a P-type NiO layer 4 on the surface of the gallium oxide epitaxial layer 2 and at the bottom of the secondary trench; next, metal Ni is deposited, and the metal Ni layer 5 forms a Schottky contact with the gallium oxide epitaxial layer 2 on the trench sidewall to form a Schottky diode, and forms an ohmic contact with the P-type NiO layer 4; finally, SiO2 is deposited on the metal Ni layer 5 to form a passivation layer 6, and a portion of the metal Ni is patterned to expose as a contact electrode.

[0043] Figure 3This is a schematic diagram of the current conduction of the multi-level trench self-protected Schottky diode device in this embodiment. In this embodiment, a two-level trench is used for the epitaxial layer. P-type NiO is deposited at the bottom of the trench and on the surface of the epitaxial layer to form a heterojunction. This effectively protects the Schottky barrier on the sidewalls, avoiding excessive leakage current. Simultaneously, it allows the current to flow along the (010) plane after the device is turned on, i.e., in the direction of maximum carrier mobility. This compensates for the increased resistance caused by the JFET region formed by the heterojunction, thus the overall on-resistance does not increase. When the current flows below the P-type NiO, a potential difference is generated between the metal electrode and below the P-type NiO, causing the heterojunction to turn on earlier, and improving the device's surge resistance.

[0044] Example 2

[0045] This embodiment provides a multi-level trench self-protected Schottky diode device structure, as follows: Figure 4 As shown, a cathode 3 is deposited on the bottom side of a gallium oxide substrate 1, and a gallium oxide epitaxial layer 2 is deposited on the top side of the gallium oxide substrate 1. A secondary trench is provided on the upper part of the gallium oxide epitaxial layer 2, and the opening distance of the first sub-trench is greater than that of the second sub-trench. A P-type NiO layer 4 is deposited on the surface of the gallium oxide epitaxial layer 2 and at the bottom of the first and second sub-trenches. The P-type NiO layer 4 at the bottom of the second sub-trench is discontinuous. A metallic Ni layer 5 is deposited on the entire epitaxial layer and the surface of the secondary trench. The metallic Ni layer 5 forms a Schottky contact with the sidewall of the trench and the gallium oxide epitaxial layer 2 at the bottom of the second sub-trench to form a Schottky diode, and forms an ohmic contact with the P-type NiO layer 4. A SiO2 passivation layer 6 filling the secondary trench is deposited on the surface of the metallic Ni layer 5.

[0046] Example 3

[0047] This embodiment provides a multi-level trench self-protected Schottky diode device structure, as follows: Figure 5 As shown, a cathode 3 is deposited on the bottom side of a gallium oxide substrate 1, and a gallium oxide epitaxial layer 2 is deposited on the top side of the gallium oxide substrate 1. A secondary trench is provided on the upper part of the gallium oxide epitaxial layer 2, and the opening distance of the first sub-trench is greater than that of the second sub-trench. A high-resistivity region 4 is provided on the surface of the gallium oxide epitaxial layer 2 and at the bottom of the first and second sub-trenches. The high-resistivity regions 401 and 403 on the surface of the gallium oxide epitaxial layer 2 and at the bottom of the second sub-trench are deposited P-type NiO layers. The high-resistivity region 402 at the bottom of the first sub-trench is formed by ion implantation of N element into the gallium oxide epitaxial layer. A metallic Ni layer 5 is deposited on the entire epitaxial layer and the surface of the secondary trench. The metallic Ni layer 5 forms a Schottky contact with the gallium oxide epitaxial layer 2 on the trench sidewall to form a Schottky diode, and forms an ohmic contact with the P-type NiO layer 4. A SiO2 passivation layer 6 filling the secondary trench is deposited on the surface of the metallic Ni layer 5.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-level trench self-protected Schottky diode device, characterized in that, include: A gallium oxide substrate, a gallium oxide epitaxial layer located on the upper side of the gallium oxide substrate, a multi-level trench provided on the upper part of the gallium oxide epitaxial layer, the multi-level trench including M≥2 sub-trenches, the first-level sub-trench to the Mth-level sub-trench successively approaching the gallium oxide substrate and their opening distance successively decreasing, a high-resistivity region provided on the surface of the gallium oxide epitaxial layer and the bottom of the multi-level trenches, a Schottky metal deposited on the surface of the multi-level trenches, the Schottky metal forming a Schottky contact with the gallium oxide epitaxial layer, and the Schottky metal forming an ohmic contact with the high-resistivity region; The Schottky contact portion is located on the sidewall of the multi-level trench.

2. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The high-resistivity region was formed by P-type oxide deposition.

3. The multi-level trench self-protected Schottky diode device according to claim 2, characterized in that, The p-type oxide is one of NiO and Cu2O.

4. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The high-resistivity region is formed by ion implantation of the gallium oxide epitaxial layer at the bottom of the multi-level trench.

5. The multi-level trench self-protected Schottky diode device according to claim 4, characterized in that, The ion implanted element is one of N or Mg.

6. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The Schottky contact portion is located on the sidewall of the multi-level trench, and part of it is located at the bottom of the multi-level trench.

7. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The high-resistivity region is partly formed by P-type oxide deposition and partly by ion implantation of the gallium oxide epitaxial layer at the bottom of the multi-level trench.

8. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The bottom side of the gallium oxide substrate is deposited with cathode metal.

9. The multi-level trench self-protected Schottky diode device according to claim 1, characterized in that, The Schottky metal surface is deposited with a passivation layer formed by an insulating medium.

10. A method for fabricating a multi-level trench self-protected Schottky diode device according to any one of claims 1 to 9, characterized in that, Includes the following steps: The gallium oxide epitaxial layer is etched to form a multi-level trench including M-level sub-trenches; A high-resistivity region is formed on the surface of the gallium oxide epitaxial layer and at the bottom of the multi-level trench; Schottky metal is deposited on the surface of the multi-level trenches to form a Schottky contact with the gallium oxide epitaxial layer and an ohmic contact with the high-resistivity region.

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