Gallium oxide Schottky diode capable of resisting neutron single-particle burning and preparation method of gallium oxide Schottky diode

Abstract

The invention relates to the technical field of semiconductor power devices, and discloses a gallium oxide Schottky diode resistant to neutron single particle burning and a preparation method thereof, the diode comprises a gallium oxide substrate, an N-type drift layer located on the gallium oxide substrate, an anode Schottky contact and a cathode ohmic contact located on the N-type drift layer, and a composite terminal structure; the composite terminal structure is arranged in an anode edge region of the N-type drift layer and comprises field limiting rings and junction terminal extensions, the field limiting rings are a plurality of P-type doped annular regions, the junction terminal extensions are N-type lightly doped regions surrounding the outmost field limiting rings, and the N-type doping concentration of the junction terminal extensions is lower than that of the N-type drift layer. The method is used for preparing the diode. According to the gallium oxide Schottky diode, the gallium oxide Schottky diode shows excellent single particle burning threshold voltage in an atmosphere neutron irradiation environment, the reliability of the gallium oxide Schottky diode in the radiation environment is improved, and the service life of the gallium oxide Schottky diode in the radiation environment is prolonged.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor power devices, and particularly relates to a gallium oxide Schottky diode resistant to neutron single event burnout and a preparation method thereof. BACKGROUND

[0002] As a new generation of ultra-wide bandgap semiconductor material, gallium oxide has the advantages of high breakdown electric field and low on-resistance in power devices. However, the reliability problem of gallium oxide in a radiation environment is particularly prominent, especially the single event burnout effect caused by atmospheric neutron irradiation, which has become a key bottleneck restricting its application in the field of high reliability.

[0003] The conventional gallium oxide Schottky diode usually adopts a single terminal structure, such as one of a field limiting ring and a junction termination extension, which has limitations in the ability to suppress electric field concentration and is difficult to effectively resist the local electric field peak and thermal runaway caused by neutron irradiation. In addition, the conventional Schottky metal material also has deficiencies in radiation resistance and thermal stability, which further reduces the working reliability of the device in a radiation environment.

[0004] Therefore, there is an urgent need for a gallium oxide Schottky diode capable of improving the ability of gallium oxide Schottky diode to resist neutron single event burnout. SUMMARY

[0005] The application aims to provide a gallium oxide Schottky diode resistant to neutron single event burnout and a preparation method thereof, so as to solve the technical problems in the background.

[0006] To achieve the above-mentioned purpose, the application discloses the following technical solutions: In a first aspect, the application discloses a gallium oxide Schottky diode resistant to neutron single event burnout, comprising a gallium oxide substrate, an N-type drift layer located on the gallium oxide substrate, an anode Schottky contact located on the N-type drift layer, and a cathode ohmic contact, and further comprising a composite terminal structure. The composite terminal structure is arranged at the anode edge region of the N-type drift layer and comprises a field limiting ring and a junction termination extension, wherein the field limiting ring is a plurality of P-type doped ring-shaped regions, the junction termination extension is an N-type lightly doped region surrounded outside the outermost field limiting ring, and the N-type doping concentration of the junction termination extension is lower than that of the N-type drift layer. The metal material of the anode Schottky contact is platinum oxide.

[0007] Optionally, the number of the field limiting rings is 3-5, the ring width is 2-5 mu m, the spacing between two adjacent field limiting rings gradually increases from inside to outside, and the increasing amplitude is 0.5-1.5 mu m.

[0008] Optionally, the lateral width of the junction terminal extension is 10 μm to 30 μm, and its nitrogen-type doping concentration is one-fifth to one-half of the doping concentration of the N-type drift layer.

[0009] Optionally, the anode Schottky contact is formed by thermal oxidation of a platinum metal layer, with a barrier height of 1.3 eV to 1.6 eV.

[0010] Secondly, this application discloses a method for preparing a gallium oxide Schottky diode resistant to neutron single-particle burn-off as described above, the method comprising the following steps: Step S1: Epitaxially grow an N-type drift layer on a gallium oxide substrate; Step S2: A silicon dioxide layer as an ion implantation mask is deposited on the surface of the N-type drift layer. A first implantation window is formed on the silicon dioxide layer by a first photolithography and etching process. Ion implantation is performed through the first implantation window to form a field confinement ring in the N-type drift layer. The field confinement ring is a ring-shaped region doped with multiple P-type types. Step S3: A second implantation window is formed on the silicon dioxide layer by a second photolithography and etching process. Ion implantation is performed through the second implantation window to form a junction termination extension in the N-type drift layer outside the field confinement ring, wherein the junction termination extension is an N-type lightly doped region. Step S4: Remove the silicon dioxide layer and perform high-temperature annealing on the device structure formed by the gallium oxide substrate, the N-type drift layer, the field confinement ring, and the junction termination extension; Step S5: A platinum metal layer is deposited on the front side of the device structure by electron beam evaporation, and an anode metal layer is patterned using photolithography and lift-off techniques; Step S6: Perform rapid thermal annealing on the anode metal layer in an oxygen-containing environment to convert its surface into platinum oxide, forming an anode Schottky contact; Step S7: Deposit a cathode ohmic contact consisting of a titanium layer and a gold layer stacked sequentially on the back side of the gallium oxide substrate.

[0011] Optionally, in step S2, the ions injected through the first injection window are Mg ions, the injection energy is 150 keV to 250 keV, and the injection dose is 1 × 10⁻⁶. 13 cm -2 Up to 3×10 13 cm -2 .

[0012] Optionally, in step S3, the ions implanted through the second implantation window are Si ions, the implantation energy is 80keV to 150keV, and the implantation dose is 5×10⁻⁶. 11 cm -2 Up to 2×1012 cm -2 .

[0013] Optionally, the high-temperature annealing in step S4 is carried out in a nitrogen atmosphere, with an annealing temperature of 1000°C to 1100°C and an annealing time of 15 min to 25 min.

[0014] Optionally, the oxygen-containing environment in step S6 is a mixed gas environment of oxygen and argon, wherein the oxygen volume ratio is 20% to 40%, the annealing temperature is 580°C to 620°C, and the annealing time is 2 min to 4 min.

[0015] Optionally, the platinum metal layer deposition thickness in step S5 is 80 nm to 150 nm; In step S7, the deposition thickness of the titanium layer is 15 nm to 25 nm, and the deposition thickness of the gold layer is 200 nm to 400 nm.

[0016] Beneficial Effects: The gallium oxide Schottky diode resistant to neutron single-particle burn-out and its fabrication method of this application, by setting a composite termination structure composed of a field-limiting ring and a junction termination extension, combined with a high-barrier platinum oxide Schottky contact, achieves multi-level smoothing and optimized distribution of the electric field in the termination region. This reduces the risk of electric field concentration and current accumulation in the gallium oxide Schottky diode under neutron irradiation. Furthermore, the composite termination structure can synergistically suppress the peak electric field at the anode edge. Simultaneously, the high thermal stability and high barrier characteristics of platinum oxide further enhance the thermal runaway resistance of the gallium oxide Schottky diode. Ultimately, this results in a gallium oxide Schottky diode exhibiting excellent single-particle burn-out threshold voltage under atmospheric neutron irradiation, improving its reliability and lifespan in radiation environments. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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.

[0018] Figure 1 This is a schematic diagram of the structure of a gallium oxide Schottky diode resistant to neutron single-particle burn-off provided in an embodiment of this application; Figure 2 This is a schematic diagram illustrating the fabrication method of the gallium oxide Schottky diode resistant to neutron single-particle burn-off provided in an embodiment of this application.

[0019] Reference numerals: 101, gallium oxide substrate; 102, N-type drift layer; 103, anode Schottky contact; 104, cathode ohmic contact; 201, field confinement ring; 202, junction termination extension. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In this document, the term "comprising" is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0022] This embodiment provides, in a first aspect, a method such as Figure 1 The gallium oxide Schottky diode shown is resistant to neutron single-particle burn-off and includes a gallium oxide substrate 101, an N-type drift layer 102 on the gallium oxide substrate 101, an anode Schottky contact 103 on the N-type drift layer 102, and a cathode ohmic contact 104. It also includes a composite termination structure, which is a protective structure specifically designed at the edge of the active region of the device to improve the electric field distribution. Specifically, the composite termination structure is disposed in the anode edge region of the N-type drift layer 102, which includes a field-limiting ring 201 and a junction termination extension 202. The field-limiting ring 201 is a ring-shaped region formed by ion implantation with multiple P-type doped structures. Its conductivity type is opposite to that of the N-type drift layer. It withstands reverse bias in stages by forming multiple PN junctions. The junction termination extension 202 is a lightly doped N-type region surrounding the outermost field-limiting ring 201. That is, it is a resistive region formed by light doping outside the field-limiting ring 201. It widens the depletion region by reducing the surface doping concentration, and the N-type doping concentration of the junction termination extension 202 is lower than that of the N-type drift layer 102. The metal material of the anode Schottky contact 103 is platinum oxide. Platinum oxide is a Schottky contact material formed by thermally oxidizing platinum metal, which has a high barrier height.

[0023] Based on the above, the gallium oxide Schottky diode in this embodiment, through the synergistic design of the composite termination structure, utilizes the field limiting ring 201 to share the electric field peak at the anode edge, while the junction termination extension 202 provides a smooth electric field transition region. This combined design effectively suppresses electric field concentration and reduces the risk of local electric field spikes in the gallium oxide Schottky diode under neutron irradiation. Simultaneously, the high barrier characteristic of the anode Schottky contact 103 reduces reverse leakage current, improves the stability of the gallium oxide Schottky diode under radiation environments, and enhances its resistance to single-event burn-out.

[0024] In one feasible implementation, the number of field limiting loops 201 is 3 to 5. Figure 1 (Only one is shown for illustration) The ring width is 2μm to 5μm, and the spacing between two adjacent field limiting rings 201 gradually increases from the inside to the outside, with an increase of 0.5μm to 1.5μm. Here, ring width refers to the radial dimension of each field limiting ring 201; the gradient spacing design means that the distance between adjacent rings increases sequentially from the innermost field limiting ring to the outermost field limiting ring.

[0025] Based on the above, the gradient spacing design conforms to the natural attenuation law of the electric field in the terminal region. The denser arrangement of the inner rings effectively distributes the high electric field area, while the sparser arrangement of the outer rings adapts to the attenuation of the electric field. This optimized layout ensures that the electric field is evenly distributed between the rings, avoiding premature breakdown of specific rings and improving the overall withstand voltage and reliability of the composite terminal structure.

[0026] In one feasible implementation, the lateral width of the junction termination extension 202 is 10 μm to 30 μm, and its nitrogen-type doping concentration is one-fifth to one-half of the doping concentration of the N-type drift layer 102. Here, the lateral width refers to the dimension of the junction termination extension 202 from the outermost edge of the field confinement ring to the outer boundary of the termination region; light doping refers to a doping concentration significantly lower than the doping level of the N-type drift layer 102.

[0027] Based on the above, the moderately reduced doping concentration makes the junction termination extension 202 more easily depleted, effectively expanding the depletion region width. When used in conjunction with the field limiting ring 201, the junction termination extension 202 acts as an electric field buffer layer, gradually reducing the remaining electric field to zero, eliminating electric field concentration at the edge of the termination region, and improving the reliability of the gallium oxide Schottky diode under radiation conditions.

[0028] In one feasible implementation, the anode Schottky contact 103 is formed by thermal oxidation of a platinum metal layer, with a barrier height of 1.3 eV to 1.6 eV. Here, barrier height refers to the band difference between the metal and semiconductor in the Schottky junction; thermal oxidation refers to the process of converting the platinum metal surface into platinum oxide by heating in an oxygen-containing environment.

[0029] Based on the above, the higher Schottky barrier reduces the leakage current density under reverse bias, while the excellent thermal stability of platinum oxide ensures the stability of the barrier height under high temperature conditions, providing a wider safe operating area for gallium oxide Schottky diodes in radiation environments.

[0030] This embodiment provides a second aspect as follows: Figure 2 The method shown is used to fabricate the gallium oxide Schottky diode resistant to neutron single-particle burn-off as described above. The method includes: Step S1: Epitaxially grow an N-type drift layer 102 on a gallium oxide substrate 101; Step S2: A silicon dioxide layer as an ion implantation mask is deposited on the surface of the N-type drift layer 102. The silicon dioxide mask layer is used to provide precise implantation pattern definition. A first implantation window is formed on the silicon dioxide layer through a first photolithography and etching process. Ion implantation is performed through the first implantation window to form a field confinement ring 201 within the N-type drift layer 102, wherein the field confinement ring 201 is a ring-shaped region of multiple P-type doped regions. Step S3: A second implantation window is formed on the silicon dioxide layer through a second photolithography and etching process. Ion implantation is performed through the second implantation window to form a junction termination extension 202 in the N-type drift layer 102 outside the field confinement ring 201, wherein the junction termination extension 202 is an N-type lightly doped region. Step S4: Remove the silicon dioxide layer and perform high-temperature annealing on the device structure consisting of gallium oxide substrate 101, N-type drift layer 102, field confinement ring 201 and junction termination extension 202 to activate doped ions and repair implantation damage. Step S5: Deposit a platinum metal layer on the front side of the device structure by electron beam evaporation, and pattern the anode metal layer using photolithography and lift-off techniques; Step S6: Perform rapid thermal annealing on the anode metal layer in an oxygen-containing environment to convert its surface into platinum oxide, forming the anode Schottky contact 103; Step S7: A cathode ohmic contact 104 consisting of a titanium layer and a gold layer stacked sequentially is deposited on the back side of the gallium oxide substrate 101. The titanium / gold stack provides a stable ohmic contact.

[0031] Based on the above, the fabrication method of this embodiment achieves precise manufacturing of the composite terminal structure through a stepwise implantation process, ensuring that the doping distribution of the field confinement ring and junction terminal extension meets the design expectations. High-temperature annealing effectively activates the implanted ions and repairs lattice damage, while the platinum oxide formation process creates a high-quality Schottky junction, ultimately producing a complete gallium oxide Schottky diode device with high resistance to neutron single-particle burn-off.

[0032] In one feasible implementation, in step S2, the ions injected through the first injection window are Mg ions, the injection energy is 150keV to 250keV, and the injection dose is 1×10⁻⁶. 13 cm -2 Up to 3×10 13 cm -2 In this study, Mg ions were used as a p-type dopant, and their implantation parameters were optimized to ensure the formation of a stable acceptor level in gallium oxide. The implantation energy was 150-250 keV, controlling the junction depth within the range of 0.5-1.0 μm, and the dose was 1 × 10⁻⁶. 13 cm -2 Up to 3×10 13 cm -2 Ensure that the required acceptor concentration is obtained.

[0033] Based on the above, by limiting the Mg ion implantation parameters, the formed field-limiting ring 201 is ensured to have a precise doping distribution and junction depth, forming a stable P-type region. Furthermore, the appropriate acceptor concentration ensures that the formed field-limiting ring 201 can be effectively depleted under reverse bias, achieving a uniform electric field distribution, thereby improving the single-particle burn-off resistance of the prepared gallium oxide Schottky diode.

[0034] In one feasible implementation, in step S3, the ions implanted through the second implantation window are Si ions, the implantation energy is 80keV to 150keV, and the implantation dose is 5×10⁻⁶. 11 cm -2 Up to 2×10 12 cm -2 In this process, Si ions are used as N-type dopant to form junction termination extension. Lower implantation energy and dose achieve light doping characteristics; implantation energy of 80-150 keV corresponds to a shallower junction depth, and dose of 5 × 10⁻⁶ keV is used. 11 cm -2 Up to 2×10 12 cm -2 Ensure that the doping concentration is significantly lower than that of the drift layer.

[0035] Based on the above, precisely controlled light doping gives the junction termination extension 202 a moderate resistivity, enabling smooth depletion under reverse bias. This design extends the depletion region width, smooths the electric field distribution in the termination region, and avoids sudden increases in the electric field at the structure edges. When neutron irradiation generates electron-hole pairs, the optimized electric field distribution prevents local carrier accumulation and suppresses thermal runaway.

[0036] In one feasible implementation, the high-temperature annealing in step S4 is performed in a nitrogen atmosphere at a temperature of 1000°C to 1100°C for 15 to 25 minutes. The high-temperature annealing process is carried out under nitrogen protection to prevent the gallium oxide material from decomposing at high temperatures. The temperature range of 1000-1100°C and the annealing time of 15-25 minutes are optimized to minimize material damage while fully activating the dopant.

[0037] Based on the above, by designing high-temperature annealing conditions to ensure full activation of implanted ions, stable electrical properties were achieved. Simultaneously, this process repaired lattice damage caused by ion implantation, improved material crystallinity, reduced defect-assisted tunneling current, lowered the risk of carrier multiplication under neutron irradiation, and improved the overall reliability of the fabricated gallium oxide Schottky diode.

[0038] In one feasible implementation, the oxygen-containing environment in step S6 is a mixture of oxygen and argon, wherein the oxygen volume percentage is 20% to 40%, the annealing temperature is 580°C to 620°C, and the annealing time is 2 to 4 minutes. The platinum oxide formation process uses a controllable oxygen ratio of 20%-40% and a suitable temperature range of 580-620°C to ensure sufficient oxidation while avoiding over-reaction. Furthermore, the short annealing time of 2-4 minutes ensures the formation of the interface layer without compromising the integrity of the metal layer.

[0039] Based on the above, a uniform and dense platinum oxide layer was formed on the surface of the platinum metal layer by designing oxidation conditions, thereby obtaining a high-quality Schottky interface. Furthermore, an appropriate degree of oxidation ensured that the barrier height remained within the ideal range of 1.3-1.6 eV, while maintaining good interface state characteristics. This controlled interface engineering improved the reverse characteristics of the fabricated gallium oxide Schottky diode and enhanced its resistance to single-particle burn-off.

[0040] In one feasible implementation, the platinum metal layer in step S5 has a deposition thickness of 80 nm to 150 nm, thereby ensuring sufficient material for platinum oxide formation while maintaining good electrical conductivity. In step S7, the titanium layer has a deposition thickness of 15 nm to 25 nm, and the gold layer has a deposition thickness of 200 nm to 400 nm, wherein the titanium layer serves as an adhesion layer and a diffusion barrier layer, and the gold layer provides low-resistance contact and good bonding properties.

[0041] Based on the above, the electrical performance and process reliability were balanced by designing the metal layer thickness, ensuring that the Schottky contact remains intact after oxidation, while the titanium / gold stack structure provides a stable ohmic contact. This metallization scheme guarantees the long-term stability of the fabricated gallium oxide Schottky diode under high temperature and high current stress, and especially demonstrates excellent reliability under neutron irradiation.

[0042] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 gallium oxide Schottky diode against neutron single event burnout, comprising a gallium oxide substrate (101), an N-type drift layer (102) located on the gallium oxide substrate (101), an anode Schottky contact (103) located on the N-type drift layer (102), and a cathode ohmic contact (104), characterized in that, Also comprising a complex termination structure; The complex termination structure is arranged at an anode edge region of the N-type drift layer (102), and comprises a field-limiting ring (201) and a junction termination extension (202), wherein the field-limiting ring (201) is a plurality of P-type doped annular regions, the junction termination extension (202) is an N-type lightly doped region outside the outermost field-limiting ring (201), and the N-type doping concentration of the junction termination extension (202) is lower than that of the N-type drift layer (102); The metal material of the anode Schottky contact (103) is platinum oxide.

2. The gallium oxide Schottky diode resistant to neutron single event burnout according to claim 1, characterized in that, The number of the field-limiting ring (201) is 3-5, the ring width is 2-5 μm, the spacing between two adjacent field-limiting rings (201) gradually increases from inside to outside, and the increasing range is 0.5-1.5 μm.

3. The gallium oxide Schottky diode resistant to neutron single event burnout according to claim 1, characterized in that, The lateral width of the junction termination extension (202) is 10-30 μm, and the N-type doping concentration thereof is one-fifth to one-half of the doping concentration of the N-type drift layer (102).

4. The gallium oxide Schottky diode resistant to neutron single event burnout according to claim 1, wherein The anode Schottky contact (103) is formed by thermal oxidation of a platinum metal layer, and the barrier height thereof is 1.3-1.6 eV.

5. A method of making a gallium oxide Schottky diode resistant to neutron single event burnout as claimed in any one of claims 1 to 4, characterised in that, The method comprises the following steps: Step S1: epitaxially growing an N-type drift layer (102) on a gallium oxide substrate (101); Step S2: depositing a silicon dioxide layer on the surface of the N-type drift layer (102) as an ion implantation mask, forming a first implantation window on the silicon dioxide layer by a first photolithography and etching process, and performing ion implantation through the first implantation window to form a field-limiting ring (201) in the N-type drift layer (102), wherein the field-limiting ring (201) is a plurality of P-type doped annular regions; Step S3: forming a second implantation window on the silicon dioxide layer by a second photolithography and etching process, and performing ion implantation through the second implantation window to form a junction termination extension (202) in the N-type drift layer (102) outside the field-limiting ring (201), wherein the junction termination extension (202) is an N-type lightly doped region; Step S4: removing the silicon dioxide layer, and performing high-temperature annealing on the device structure composed of the gallium oxide substrate (101), the N-type drift layer (102), the field-limiting ring (201), and the junction termination extension (202); Step S5: depositing a platinum metal layer on the front surface of the device structure by electron beam evaporation, and patterning the anode metal layer by photolithography and stripping technology; Step S6: performing rapid thermal annealing treatment on the anode metal layer in an oxygen-containing environment to convert the surface thereof into platinum oxide, thereby forming an anode Schottky contact (103); Step S7: depositing a cathode ohmic contact (104) composed of a titanium layer and a gold layer on the back surface of the gallium oxide substrate (101).

6. The method of claim 5, wherein, In the step S2, the ions injected through the first injection window are Mg ions, the injection energy is 150 keV to 250 keV, and the injection dose is 1 x 1016cm 13 to 3 x 1016cm -2 . 13 to 3 x 1016cm -2 .

7. The method of claim 5, wherein, In the step S3, the ions injected through the second injection window are Si ions, the injection energy is 80 keV to 150 keV, and the injection dose is 5 x 1013cm 11 to 2 x 1014cm -2 . 12 to 2 x 1014cm -2 .

8. The method of claim 5, wherein, The high-temperature annealing in step S4 is performed in a nitrogen environment, the annealing temperature is 1000-1100 °C, and the annealing time is 15-25 min.

9. The method of claim 5, wherein, The oxygen-containing environment in the step S6 is a mixed gas environment of oxygen and argon, wherein the volume percentage of oxygen is 20% to 40%, the annealing temperature is 580°C to 620°C, and the annealing time is 2 min to 4 min.

10. The method of claim 5, wherein, The deposition thickness of the platinum metal layer in the step S5 is 80 nm to 150 nm. In the step S7, the deposition thickness of the titanium layer is 15 nm to 25 nm, and the deposition thickness of the gold layer is 200 nm to 400 nm.

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