Ampere-level gallium oxide Schottky barrier diode based on field plate structure and preparation method of ampere-level gallium oxide Schottky barrier diode

Abstract

The invention discloses an ampere-level gallium oxide Schottky barrier diode based on a field plate structure and a preparation method of the ampere-level gallium oxide Schottky barrier diode. The preparation method comprises the following steps: preparing a gallium monoxide substrate; growing SiO2 on the gallium oxide substrate, and annealing in an oxygen atmosphere in rapid thermal annealing equipment; etching the back of the gallium oxide substrate, washing off SiO2 on the surface of the gallium oxide substrate by using hydrofluoric acid, and growing a mark layer on the gallium oxide substrate; growing a back cathode electrode; annealing the sample in a nitrogen atmosphere to form ohmic contact; growing a field plate aluminum oxide medium; and growing an anode electrode on the top of the device. According to the technical scheme provided by the invention, the problem of preparing the ampere-level gallium oxide Schottky barrier diode under the condition of maintaining high breakdown voltage of the device is solved.

Description

Technical Field

[0001] This invention relates to the field of power device technology, and in particular to an ampere-level gallium oxide Schottky barrier diode based on a field plate structure and its fabrication method. Background Technology

[0002] Gallium oxide (GaO), as an emerging ultra-wide bandgap semiconductor material, possesses significant potential in high-voltage, low-loss, and low-cost power devices due to its advantages such as large bandgap, high breakdown field strength, fast saturated electron drift velocity, and low-cost melt fabrication method. Because GaO has a relatively flat valence band and is difficult to p-type doped, GaO Schottky barrier diodes (SBDs) are currently the mainstream devices. Breakdown voltage is one of the most important indicators of SBD devices, closely related to their power consumption and reliability. However, as the active area increases, defect aggregation leads to increased leakage current, severely affecting device performance and reliability, becoming a key bottleneck restricting practical application. Therefore, developing a high-current, high-voltage GaO Schottky barrier diode through surface annealing combined with field plate structure design, thereby improving both the breakdown voltage and forward conduction current and enhancing the electrical performance of the Schottky device, has become a key technical focus urgently needed by those skilled in the art. Summary of the Invention

[0003] To address the shortcomings of the existing technology, this invention provides an ampere-level gallium oxide Schottky barrier diode based on a field plate structure and its fabrication method, thereby solving the problem of how to fabricate a high-voltage gallium oxide Schottky barrier diode while ensuring high current. The technical solution of this invention is described in detail below.

[0004] This invention provides a method for fabricating an ampere-level gallium oxide Schottky barrier diode based on a field plate structure, comprising the following steps: (1) Prepare a gallium monoxide substrate; (2) SiO2 is grown on a gallium oxide substrate and then annealed in an oxygen atmosphere to repair interface defects on the gallium oxide substrate; (3) The back of the gallium oxide substrate is etched, and the SiO2 on the surface of the gallium oxide substrate is washed away with hydrofluoric acid. Then, a marking layer is grown on the gallium oxide substrate to facilitate the subsequent patterning of the alumina field oxygen medium. (4) Growing cathode metal on the back side of the gallium oxide substrate; (5) Anneal the sample in a nitrogen atmosphere to form an ohmic contact; (6) A patterned alumina field oxygen dielectric layer is grown on a gallium oxide substrate; (7) Grow anode metal on top of the device.

[0005] In this invention, in step (1), the gallium oxide substrate comprises a highly doped gallium oxide single crystal substrate and a lightly doped gallium oxide single crystal epitaxial layer; the doping concentration of the highly doped gallium oxide single crystal substrate is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The thickness ranges from 100 μm to 1000 μm, and the doping concentration of the low-doped gallium oxide single crystal epitaxial layer is 1 × 10⁻⁶. 15 cm -3 ~5×10 16 cm -3 The thickness ranges from 5μm to 100μm.

[0006] In this invention, in step (2), SiO2 is grown using plasma-enhanced chemical vapor deposition with a thickness of 80-120 nm; under an oxygen atmosphere, the annealing temperature is 395-405 °C and the annealing time is 50-70 min. The introduction of the SiO2 layer is to prevent impurities in the annealing equipment from contaminating the gallium oxide interface and to inhibit the decomposition of gallium oxide at high temperatures.

[0007] In this invention, in step (3), an inductively coupled plasma device is used for etching.

[0008] In this invention, in step (4), a physical vapor deposition device is used to grow a cathode, which is a Ti / Au electrode with a Ti thickness of 40-60 nm and an Au thickness of 190-210 nm; in step (7), an electron beam evaporation device is used to grow an anode, which is a Ni / Au electrode with a Ni thickness of 40-60 nm and an Au thickness of 190-210 nm.

[0009] In this invention, in step (5), the annealing temperature is 465-475℃ and the annealing time is 50-70s.

[0010] In this invention, in step (6), a patterned alumina field oxygen dielectric layer is grown by atomic layer deposition, with a growth rate of 0.10-0.15 nm / cycle and a growth temperature of 240-260℃.

[0011] In this invention, the alumina field oxygen dielectric layer is annular when viewed from above, and the top anode layer is circular when viewed from above, with the centers of the annular and circular layers coinciding; the length of the overlapping area between the top anode layer and the alumina field oxygen dielectric layer is 14-16 μm; and the diameter of the top anode electrode layer is 1180-1220 μm.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention has a simple process. It mainly achieves ampere-level high current and high voltage on large-area devices by combining surface oxygen annealing treatment and field plate termination. It solves the problem of fabricating ampere-level gallium oxide Schottky barrier diodes while maintaining the high breakdown voltage of the device. Attached Figure Description

[0013] 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.

[0014] Figure 1 This is a schematic diagram of a traditional gallium oxide Schottky barrier diode structure.

[0015] Figure 2 This is a schematic flowchart of a method for fabricating an ampere-level gallium oxide Schottky barrier diode based on a field plate structure according to an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of the structure of an ampere-level gallium oxide Schottky barrier diode based on a field plate structure, provided in a typical embodiment of the present invention.

[0017] Figure 4 This is a current-voltage diagram of gallium oxide Schottky barrier diodes without surface annealing and without a field plate, and with surface annealing and with a field plate, under reverse voltage.

[0018] Figure 5 This is a current-voltage diagram of gallium oxide Schottky barrier diodes with and without surface annealing and with surface annealing and with a field plate under forward voltage.

[0019] Explanation of reference numerals in the attached figures: 101-Back Ti / Au electrode; 102-Gallium oxide single crystal substrate; 103-Patterned top Ni / Au electrode; 201-Back Ti / Au electrode; 202-Heavily doped gallium oxide single crystal substrate; 203-Lowly doped gallium oxide epitaxial layer; 204-High temperature oxygen atmosphere annealing region; 205-Patterned alumina field oxygen medium; 206-Patterned top Ni / Au electrode. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0022] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0023] Traditional gallium oxide Schottky barrier diodes are fabricated on a gallium oxide single-crystal substrate by patterning a top Schottky electrode. The structure of a traditional gallium oxide Schottky barrier diode is as follows: Figure 1 As shown, it specifically includes: a gallium oxide substrate 102; a patterned top electrode layer 103 along the direction away from the gallium oxide substrate; and a bottom electrode layer 101 on the back side along the direction close to the gallium oxide substrate; According to an embodiment of the present invention, a method for fabricating a gallium oxide Schottky barrier diode is provided, which is applied in low electric field operation. A schematic flowchart of the method is shown below. Figure 2 As shown, the method includes: S11: Provides gallium monoxide substrate 202; In one specific embodiment, the gallium oxide substrate includes a highly doped gallium oxide single crystal substrate 202 and a low-doped gallium oxide single crystal epitaxial layer 203 formed on the surface of the highly doped gallium oxide single crystal substrate; the low-doped gallium oxide single crystal epitaxial layer is formed by halide vapor deposition on the surface of the highly doped gallium oxide single crystal substrate to form a single crystal gallium oxide thin film layer 203. S12: A silicon dioxide layer is grown on the epitaxial layer 203 by plasma-enhanced chemical vapor deposition to facilitate subsequent interface processing; S13: Annealing in an oxygen atmosphere using a rapid thermal annealing device; the high-temperature oxygen atmosphere annealing region 204 is formed on the surface of the gallium oxide epitaxial layer 203; S14: After high-temperature interface treatment, inductively coupled plasma back etching is performed to ensure good back ohmic contact. At the same time, hydrofluoric acid is used to remove the silicon dioxide layer on the surface to facilitate the subsequent growth of the marker layer. S15: A marking layer is grown on the epitaxial layer 203 to facilitate subsequent patterning of the alumina field oxygen medium; S16: Form a back Ti / Au electrode layer 201; the back Ti / Au electrode layer 201 is formed on the back side of the gallium oxide single crystal substrate 202 layer; S17: Annealing in a nitrogen atmosphere in a rapid thermal annealing equipment to form an ohmic contact between the back metal electrode and the highly doped substrate; S18: Forming a patterned alumina field oxygen dielectric layer 205; the patterned alumina field oxygen dielectric layer 205 is formed on the surface of the low-doped gallium oxide single crystal epitaxial layer 203; S19: Forming a patterned top Ni / Au electrode layer 206; the patterned top Ni / Au electrode layer 206 is formed on the surface of the patterned alumina field oxide dielectric layer 205; wherein, the patterned top Ni / Au electrode layer 206 and the patterned alumina field oxide dielectric layer 205 are stacked sequentially on the epitaxial layer 203 in a direction away from the epitaxial layer 203, and the top view of the patterned top Ni / Au electrode layer 206 is a circular pattern, the center of which coincides with the center of the alumina field oxide dielectric layer 205, so as to form the gallium oxide Schottky barrier diode.

[0024] The technical solution provided by the present invention will be further described in detail below with reference to the embodiments and comparative examples.

[0025] Example 1

[0026] Step S11: Provide a gallium monoxide substrate, which includes a highly doped gallium monoxide single crystal substrate 202 and a lightly doped gallium monoxide single crystal epitaxial layer 203; Step S12: A silicon dioxide layer is grown on the epitaxial layer 203 by plasma-enhanced chemical vapor deposition to facilitate subsequent interface processing; Step S13: Anneal at 400°C in an oxygen atmosphere for 1 hour using a rapid thermal annealing equipment; the high-temperature oxygen atmosphere annealing region 204 is formed on the surface of the gallium oxide epitaxial layer 203; Step S14: After high-temperature interface treatment, inductively coupled plasma back etching is performed to ensure good back ohmic contact. At the same time, hydrofluoric acid is used to remove the silicon dioxide layer on the surface to facilitate the subsequent growth of the marker layer. Step S15: A Ni layer was grown on the epitaxial layer 203 by physical vapor deposition (PVD) as a marker layer to facilitate subsequent patterning of the alumina field oxygen medium, and also to be used as an overlay marker for the alumina and the electrode. Step S16: Form a 50nm / 200nm Ti / Au electrode layer 201 on the back side; the Ti / Au electrode layer 201 on the back side of the gallium oxide single crystal substrate 202 layer; Step S17: Anneal at 470°C for 1 minute in a nitrogen atmosphere in a rapid thermal annealing apparatus to form an ohmic contact between the back metal electrode and the highly doped substrate. Step S18: Form a patterned 100nm alumina field oxygen dielectric layer 205; the patterned alumina field oxygen dielectric layer 205 is formed on the surface of the low-doped gallium oxide single crystal epitaxial layer 203; its top view is a ring with an inner diameter of 1200μm and an outer diameter of 1260μm; Step S19: Form a patterned top 50nm / 200nm Ni / Au electrode layer 206; the patterned top Ni / Au electrode layer 206 is formed on the surface of the patterned alumina field oxide dielectric layer 205; wherein, the patterned top Ni / Au electrode layer 206 and the patterned alumina field oxide dielectric layer 205 are stacked sequentially on the epitaxial layer 203 in a direction away from the epitaxial layer 203, and the top view of the patterned top Ni / Au electrode layer 206 is a circular pattern with a diameter of 1230μm, the center of which coincides with the center of the alumina field oxide dielectric layer 205, so as to form the gallium oxide Schottky barrier diode.

[0027] Example 2

[0028] Step S11: Provide a gallium monoxide substrate, which includes a highly doped gallium monoxide single crystal substrate 202 and a lightly doped gallium monoxide single crystal epitaxial layer 203; Step S16: Form a 50nm / 200nm Ti / Au electrode layer 201 on the back side; the Ti / Au electrode layer 201 on the back side of the gallium oxide single crystal substrate 202 layer; Step S17: Anneal at 470°C for 1 minute in a nitrogen atmosphere in a rapid thermal annealing apparatus to form an ohmic contact between the back metal electrode and the highly doped substrate.

[0029] Step S19: Form a patterned top 50nm / 200nm Ni / Au electrode layer 206; the patterned top Ni / Au electrode layer 206 is formed on the epitaxial layer 203, and the top view of the patterned top Ni / Au electrode layer 206 is a circular pattern with a diameter of 1200μm, in order to form the gallium oxide Schottky barrier diode. The difference between Embodiment 1 and Embodiment 2 lies in whether interface processing and field panel design were performed. Embodiment 1 performed interface processing and field panel design, while Embodiment 2 did not.

[0030] The electrical characteristics of the device were characterized using a semiconductor parameter analyzer, and the characterization results are as follows: Figure 4 and Figure 5 As shown; where: Common represents: a control group of gallium oxide Schottky barrier diodes without interface treatment and field plate design.

[0031] Sample Representative: A control group of gallium oxide Schottky barrier diodes that underwent interface processing and field plate design.

[0032] Figure 4 The reverse breakdown characteristics and statistical distribution of gallium oxide Schottky barrier diodes are shown. The average breakdown voltages of the Common group and Sample group are 800V and 1200V, respectively. Compared with the Common group, interface treatment and field plate structure can achieve higher reverse breakdown voltages. This is mainly because oxygen annealing repairs the gallium oxide interface defects, and the field plate structure also modulates the breakdown electric field at the metal edge, thereby improving the breakdown voltage of the device.

[0033] Figure 5 This is the forward conduction characteristic curve of a gallium oxide Schottky barrier diode. Considering that the current density reaches 1 A / cm²... 2 When the devices are turned on, the turn-on voltages for the Common group and Sample group are 0.83V and 0.70V, respectively, while the currents at a forward voltage of 4V are 5.35A and 2.45A, respectively. Compared to the Common group, the current in the Sample group decreases while the turn-on voltage remains almost unchanged. This is because the annealing process reduces the carrier concentration on the gallium oxide surface, thereby lowering the forward current.

[0034] Therefore, the technical solution provided by this invention, through annealing in an oxygen atmosphere and designing the field plate structure, achieves a high-voltage, high-current gallium oxide Schottky barrier diode. Although the forward current decreases somewhat, the breakdown voltage capability of the gallium oxide Schottky barrier diode device is significantly improved. Thus, this application achieves a high-current, high-voltage gallium oxide Schottky barrier diode through interface processing and termination structure, representing a significant breakthrough in this field.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating an ampere-level gallium oxide Schottky barrier diode based on a field plate structure, characterized in that, Includes the following steps: (1) Prepare a gallium monoxide substrate; (2) SiO2 is grown on a gallium oxide substrate and then annealed in an oxygen atmosphere to repair interface defects on the gallium oxide substrate; (3) The back of the gallium oxide substrate is etched, and the SiO2 on the surface of the gallium oxide substrate is washed away with hydrofluoric acid. Then, a marking layer is grown on the gallium oxide substrate to facilitate the subsequent patterning of the alumina field oxygen medium. (4) Growing cathode metal on the back side of the gallium oxide substrate; (5) Anneal the sample in a nitrogen atmosphere to form an ohmic contact; (6) A patterned alumina field oxygen dielectric layer is grown on a gallium oxide substrate; (7) Grow anode metal on top of the device.

2. The preparation method according to claim 1, characterized in that, In step (1), the gallium oxide substrate comprises a highly doped gallium oxide single crystal substrate and a lightly doped gallium oxide single crystal epitaxial layer; the doping concentration of the highly doped gallium oxide single crystal substrate is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The thickness ranges from 100 μm to 1000 μm, and the doping concentration of the low-doped gallium oxide single crystal epitaxial layer is 1 × 10⁻⁶. 15 cm -3 ~5×10 16 cm -3 The thickness ranges from 5μm to 100μm.

3. The preparation method according to claim 1, characterized in that, In step (2), SiO2 is grown by plasma-enhanced chemical vapor deposition with a thickness of 80-120 nm; under an oxygen atmosphere, the annealing temperature is 395-405 °C and the annealing time is 50-70 min.

4. The preparation method according to claim 1, characterized in that, In step (3), etching is performed using an inductively coupled plasma device.

5. The preparation method according to claim 1, characterized in that, In step (4), a physical vapor deposition device is used to grow a cathode, which is a Ti / Au electrode with a Ti thickness of 40-60 nm and an Au thickness of 190-210 nm. In step (7), an electron beam evaporation device is used to grow an anode, which is a Ni / Au electrode with a Ni thickness of 40-60 nm and an Au thickness of 190-210 nm.

6. The preparation method according to claim 1, characterized in that, In step (5), the annealing temperature is 465-475℃ and the annealing time is 50-70s.

7. The preparation method according to claim 1, characterized in that, In step (6), patterned alumina field oxygen medium is grown by atomic layer deposition at a growth rate of 0.10-0.15 nm / cycle and a growth temperature of 240-260℃.

8. The preparation method according to claim 1, characterized in that, The alumina field oxygen dielectric layer is annular when viewed from above, and the top anode layer is circular when viewed from above, with the centers of the annular and circular layers coinciding; the length of the overlap area between the top anode layer and the alumina field oxygen dielectric layer is 14-16 μm; the diameter of the top anode electrode layer is 1180-1220 μm.

9. An ampere-level gallium oxide Schottky barrier diode based on a field plate structure, prepared by the method according to any one of claims 1-8.

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