Gallium oxide-based Schottky barrier diode with low reverse electric leakage and preparation method of gallium oxide-based Schottky barrier diode

Abstract

The invention discloses a gallium oxide-based Schottky barrier diode with low reverse electric leakage and a preparation method thereof, which are applied to a high-voltage-resistant scene, and the method comprises the following steps: preparing a gallium oxide substrate; growing a mark layer on the gallium oxide substrate; performing N ion implantation by using an ion implanter to form box type distribution; then, feeding the sample into a tubular furnace, and annealing in a nitrogen atmosphere; feeding the annealed sample into electron beam evaporation equipment for back cathode growth; then sending the sample into rapid thermal annealing equipment for nitrogen atmosphere annealing to form ohmic contact; then electron beam evaporation is adopted to grow field plate oxide; and finally growing an anode on the top of the device by electron beam evaporation equipment. According to the technical scheme provided by the invention, the gallium oxide-based Schottky barrier diode with low reverse leakage characteristic can be obtained under the condition of maintaining high breakdown voltage of a device.

Description

Technical Field

[0001] This invention relates to the field of power device technology, and in particular to a gallium oxide-based Schottky barrier diode with low reverse leakage current and its fabrication method. Background Technology

[0002] Gallium oxide (GaO) is considered a strong contender for next-generation semiconductor materials due to its large bandgap, excellent carrier mobility, and radio frequency performance. Because of its relatively flat valence band and the difficulty in p-type doping, GaO Schottky barrier diodes (SBDs) are currently the mainstream devices. Breakdown voltage, one of the most important indicators of SBDs, is closely related to their power consumption and reliability. A significant problem is the electric field accumulation effect often present at the edges of the Schottky electrodes, which can lead to premature breakdown. This, to some extent, limits the application of GaO-based Schottky barrier diodes in power devices. Summary of the Invention

[0003] To address the shortcomings of the prior art, the present invention aims to provide a gallium oxide-based Schottky barrier diode with low reverse leakage current and its fabrication method. The present invention designs a high-voltage, low-reverse-leakage-current gallium oxide-based Schottky barrier diode by combining ion implantation with a breakdown structure. This diode can improve the breakdown voltage of the device while reducing the reverse leakage current, thereby enhancing the electrical performance of the Schottky device. The present invention solves the problem of how to fabricate a high-voltage, low-reverse-leakage gallium oxide-based Schottky barrier diode without sacrificing its forward characteristics.

[0004] The technical solution of the present invention is described in detail below. This invention provides a gallium oxide-based Schottky barrier diode with low reverse leakage current, characterized in that it is applied in high-voltage, low-reverse-leakage scenarios; it includes a highly doped gallium oxide single crystal substrate, a lightly doped gallium oxide single crystal epitaxial layer, a field oxide dielectric layer, a cathode electrode layer, and an anode electrode layer; the back side of the highly doped gallium oxide single crystal substrate is the cathode electrode layer, the upper surface is the lightly doped gallium oxide single crystal epitaxial layer, the surface of the lightly doped gallium oxide single crystal epitaxial layer is provided with an N-ion implantation region, the top of the device is the anode electrode layer, and the field oxide dielectric layer is located between the gallium oxide epitaxial layer and the anode electrode layer; From a top-down perspective, the anode electrode layer is circular, while the N-ion implantation region and the field oxygen dielectric layer are both annular. The centers of the N-ion implantation region, the field oxygen dielectric layer, and the anode electrode layer coincide. The inner and outer ring radii of the N-ion implantation region are smaller than the inner and outer ring radii of the field oxygen dielectric layer.

[0005] In this invention, both the highly doped gallium oxide single crystal substrate and the lightly doped gallium oxide single crystal epitaxial layer are Sn-doped gallium oxide thin films. The highly doped gallium oxide single crystal substrate has a thickness of 100-1000 μm and a doping concentration of 1×10⁻⁶.18 -1×10 19 cm -3 The thickness of the low-doped gallium oxide single-crystal epitaxial layer is 5-10 μm, and the doping concentration is between 1×10⁻⁶. 15 -1×10 16 cm -3 The thickness is 5-100μm.

[0006] In this invention, the N-ion doping concentration in the N-ion implantation region is 1 × 10⁻⁶. 18 -5×10 19 cm -3 The injection depth is 0.1-1μm.

[0007] In this invention, the cathode electrode layer uses a Ti / Au electrode, and the anode electrode layer uses a Ni / Au electrode. In a specific embodiment, the thickness of the Ti / Au electrode layer is 30nm / 100nm, and the thickness of the Ni / Au electrode is 50nm / 100nm.

[0008] In this invention, the field oxygen dielectric layer is an alumina dielectric layer. The thickness of the alumina field oxygen dielectric layer is 80-120 nm; its top view is a ring with an inner diameter of 60-64 μm and an outer diameter of 85-95 μm.

[0009] In this invention, from a top-down view, the N-ion implantation region has an inner diameter of 50-60 μm and an outer diameter of 75-85 μm. The ring is 65-70 μm in diameter, the anode electrode layer has a diameter of 65-70 μm, and the overlap region between the anode electrode layer and the field oxygen dielectric layer has a length of 4-6 μm.

[0010] The present invention also provides a method for fabricating the above-mentioned low reverse leakage gallium oxide-based Schottky barrier diode, comprising the following steps: (1) Clean the gallium oxide substrate, which includes a highly doped gallium oxide single crystal substrate layer and a low-doped gallium oxide single crystal epitaxial layer; (2) Growing a marker layer on the substrate; (3) N-ion implantation is performed in the low-doped gallium oxide single crystal epitaxial layer corresponding to the marker layer to form a box-shaped distribution using an ion implanter; (4) Annealing under a nitrogen atmosphere; (5) A cathode metal is grown on the back side of the gallium oxide substrate to form a cathode electrode layer; (6) Annealing in a nitrogen atmosphere to form an ohmic contact between the cathode metal and the substrate; (7) A field oxygen dielectric layer is grown on the surface of a gallium oxide substrate; (8) Anode metal is grown on the surface of the field oxygen dielectric layer to form an anode electrode layer.

[0011] In this invention, in step (2), a 0.1-1 μm thick metallic Ni is deposited as a marker layer by electron beam evaporation (EBE); it does not need to be removed in subsequent steps.

[0012] In this invention, step (3) can involve several N-ion implantations to form an approximately uniform distribution, i.e., a box-shaped distribution, from the epitaxial layer surface to an implantation depth of 0.1-1 μm; preferably, three N-ion implantations are performed; the energy and dose of the first implantation are 45-55 KeV, 5 × 10⁻⁶ kJ / m³. 12 cm -3 The energy and dose of the second injection were 140-160 keV, 1×10⁻⁶. 13 cm -3 The energy and dose of the third injection were 220-240 keV, 2×10⁻⁶. 13 cm -3 .

[0013] In this invention, in step (4), the annealing temperature is 1080-1120℃ and the annealing time is 25-35 minutes; in step (6), the annealing temperature is 465-475℃ and the annealing time is 40s-80s.

[0014] In this invention, in steps (5), (7) and (8), the growth method is electron beam evaporation; in step (7), the field oxygen dielectric layer is an alumina dielectric layer.

[0015] In this invention, in step (7), when the field oxygen dielectric layer is grown by electron beam evaporation, the growth process rate does not exceed 0.1 nm / s; the growth process pressure is <10. -4 Pa.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves a gallium oxide Schottky barrier diode with low reverse leakage current by introducing N-ion implantation at the Schottky edge, thereby improving the breakdown voltage of the gallium oxide Schottky barrier diode device without sacrificing its forward electrical characteristics.

[0017] This invention is the first to achieve a high-voltage, low-reverse-leakage gallium oxide Schottky barrier diode through N-ion implantation followed by annealing, representing a major breakthrough in the field. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of a traditional gallium oxide-based Schottky barrier diode structure.

[0020] Figure 2 This is a schematic flowchart of a method for fabricating a gallium oxide-based Schottky barrier diode with low reverse leakage current according to an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure of a gallium oxide-based Schottky barrier diode with low reverse leakage current provided in a typical embodiment of the present invention.

[0022] Figure 4 This is a concentration-depth simulation diagram of N-ion implantation in gallium oxide.

[0023] Figure 5 This is a current-voltage diagram of gallium oxide-based Schottky barrier diodes under reverse voltage, with and without N-ion implantation and after annealing with N-ion implantation.

[0024] Figure 6 This is a current-voltage diagram of gallium oxide-based Schottky barrier diodes with and without N-ion implantation and after annealing with N-ion implantation, under forward voltage.

[0025] 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 - Highly doped gallium oxide single crystal substrate; 203 - Lowly doped gallium oxide epitaxial layer; 204 - Patterned alumina field oxygen dielectric; 205 - Patterned top Ni / Au electrode; 206 - Patterned N-ion implantation region. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] 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.

[0029] like Figure 1 As shown, a traditional gallium oxide-based Schottky barrier diode is fabricated on a gallium oxide single-crystal substrate by patterning a top Schottky electrode. The structure of a traditional gallium oxide-based 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 patterned top electrode layer 101 stacked on the gallium oxide substrate on the back side along the direction away from the gallium oxide substrate.

[0030] According to an embodiment of the present invention, a method for fabricating a gallium oxide-based Schottky barrier diode is provided, which is applied to low reverse leakage current. 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 Sn highly doped gallium oxide single crystal substrate; the low-doped gallium oxide single crystal epitaxial layer 203 is formed by halide vapor deposition on the surface of the highly doped gallium oxide single crystal substrate 202 to form a single crystal gallium oxide thin film 203. S12: A marker layer is grown on the epitaxial layer 203 to facilitate subsequent patterning of the ion implantation region; S13: Ion implantation is performed on the epitaxial layer 203; S14: Nitrogen annealing is performed after ion implantation to activate the implanted ions; the ion implantation region 206 is formed on the surface of the gallium oxide epitaxial layer 203. S15: 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; S16: 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; S17: Forming a patterned alumina field oxygen dielectric layer 204; the patterned alumina field oxygen dielectric layer 204 is formed on the surface of the low-doped gallium oxide single crystal epitaxial layer 203; S18: Forming a patterned top Ni / Au electrode layer 205; the patterned top Ni / Au electrode layer 205 is formed on the surface of the patterned alumina field oxide dielectric layer 204; wherein, the patterned top Ni / Au electrode layer 205 and the patterned alumina field oxide dielectric layer 204 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 205 is a circular pattern, the center of which coincides with the center of the alumina field oxide dielectric layer 204, to form the gallium oxide Schottky barrier diode, the overall structure of which is shown in the schematic diagram below. Figure 3 As shown.

[0031] The technical solution provided by the present invention will be further described in detail below with reference to the embodiments.

[0032] Example 1

[0033] 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 marker layer is grown on the epitaxial layer 203 to facilitate subsequent patterning of the ion implantation area: 0.1-1 μm of metallic Ni is deposited as a marker layer by electron beam evaporation (EBE), which does not need to be removed in subsequent steps.

[0034] Step S13: Ion implantation is performed on the epitaxial layer 203; The ion implantation conditions were as follows: the energy and dose for the first implantation were 50 keV, 5 × 10⁻⁶. 12 cm -3 The energy and dose of the second injection were 150 keV, 1×10 13 cm -3 The energy and dose of the third injection were 230 keV, 2 × 10⁻⁶. 13 cm -3 Its top view shows a ring with an inner diameter of 55μm and an outer diameter of 80μm.

[0035] Figure 4 This is a concentration-depth simulation diagram of N-ion implantation in gallium oxide.

[0036] Step S14: Nitrogen annealing is performed after ion implantation to activate the implanted ions; the ion implantation region 206 is formed on the surface of the gallium oxide epitaxial layer 203; the annealing temperature is 1100℃ and the annealing time is 30 minutes. Step S15: Form a 30nm / 100nm 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 S16: 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.

[0037] Step S17: Forming a patterned 100nm alumina field oxygen dielectric layer 204; the patterned alumina field oxygen dielectric layer 204 is formed on the surface of the low-doped gallium oxide single crystal epitaxial layer 203; its top view shows a ring with an inner diameter of 60μm and an outer diameter of 90μm. The patterned alumina field oxygen dielectric layer is grown by electron beam evaporation at a process rate of 0.1 nm / s and a pressure < 10. -4 Pa.

[0038] Step S18: Form a patterned top 50nm / 100nm Ni / Au electrode layer 205; the patterned top Ni / Au electrode layer 205 is formed on the surface of the patterned alumina field oxide dielectric layer 204; wherein, the patterned top Ni / Au electrode layer 205 and the patterned alumina field oxide dielectric layer 204 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 205 is a circular pattern with a diameter of 70μm, the center of which coincides with the center of the alumina field oxide dielectric layer 204, so as to form the gallium oxide Schottky barrier diode.

[0039] Example 2

[0040] 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 S15: Form a 30nm / 100nm 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 S16: 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 S17: Form a patterned 100nm alumina field oxygen dielectric layer 204; the patterned alumina field oxygen dielectric layer 204 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 60μm and an outer diameter of 90μm; Step S18: Form a patterned top 50nm / 100nm Ni / Au electrode layer 205; the patterned top Ni / Au electrode layer 205 is formed on the surface of the patterned alumina field oxide dielectric layer 204; wherein, the patterned top Ni / Au electrode layer 205 and the patterned alumina field oxide dielectric layer 204 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 205 is a circular pattern with a diameter of 70μm, the center of which coincides with the center of the alumina field oxide dielectric layer 204, so as to form the gallium oxide Schottky barrier diode; The difference between Example 1 and Example 2 lies in whether or not N ion implantation was performed. Example 1 underwent ion implantation, while Example 2 did not.

[0041] The electrical properties of the device and the ion implantation distribution simulation were performed using a semiconductor parameter analyzer and SRIM simulation tool. The characterization results are as follows: Figures 4-6 As shown; where: w / o NIET stands for: control group gallium oxide Schottky barrier diode without N-ion implantation.

[0042] w / NIET stands for: control group gallium oxide Schottky barrier diode with N-ion implantation.

[0043] Figure 5 The reverse breakdown characteristics and statistical distribution of gallium oxide Schottky barrier diodes are shown. The average breakdown voltages of the w / o NIET group and the w / NIET group are 1223 V and 1469 V, respectively. Compared with the ordinary field plate structure, the field plate-ion implantation composite structure can achieve a higher reverse breakdown voltage. As can be seen from the figure, the average leakage current density of the w / o NIET group and the w / NIET group is 4.1 × 10⁻⁶. -2 A / cm 2 and 5.5×10 -6 A / cm 2 It can be seen that ion implantation can improve device breakdown and significantly reduce device reverse leakage current.

[0044] Figure 6 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 device is turned on, the turn-on voltages of the w / o NIET group and the w / NIET group are 0.89V and 0.95V, respectively, with a difference of only 0.06V. This indicates that the introduction of N ion implantation does not lead to a loss of positive characteristics of the device.

[0045] Therefore, the technical solution provided by this invention, by introducing N-ion implantation at the Schottky edge, realizes a gallium oxide Schottky barrier diode with low reverse leakage current, improving the breakdown voltage of the gallium oxide Schottky barrier diode device without sacrificing its forward electrical characteristics. Thus, this application is the first to achieve a high-breakthrough-voltage, low-reverse-leakage gallium oxide Schottky barrier diode through N-ion implantation followed by annealing, representing a significant breakthrough in this field.

[0046] 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 gallium oxide-based Schottky barrier diode with low reverse leakage current, characterized in that, It is used in high-voltage and low-reverse-leakage scenarios; it includes a highly doped gallium oxide single crystal substrate, a lightly doped gallium oxide single crystal epitaxial layer, a field oxygen dielectric layer, a cathode electrode layer, and an anode electrode layer; the back side of the highly doped gallium oxide single crystal substrate is the cathode electrode layer, the upper surface is the lightly doped gallium oxide single crystal epitaxial layer, the surface of the lightly doped gallium oxide single crystal epitaxial layer is provided with an N-ion implantation region, the top of the device is the anode electrode layer, and the field oxygen dielectric layer is located between the gallium oxide epitaxial layer and the anode electrode layer; From a top-down perspective, the anode electrode layer is circular, while the N-ion implantation region and the field oxygen dielectric layer are both annular. The centers of the N-ion implantation region, the field oxygen dielectric layer, and the anode electrode layer coincide. The inner and outer ring radii of the N-ion implantation region are smaller than the inner and outer ring radii of the field oxygen dielectric layer, respectively.

2. The low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, Both the highly doped gallium oxide single crystal substrate and the lightly doped gallium oxide single crystal epitaxial layer are Sn-doped gallium oxide thin films. The thickness of the gallium oxide single crystal substrate is 100-1000 μm, and the doping concentration is 1×10⁻⁶. 18 -1×10 19 cm -3 The thickness of the low-doped gallium oxide single-crystal epitaxial layer is 5-10 μm, and the doping concentration is between 1×10⁻⁶. 15 -1×10 16 cm -3 The thickness is 5-100μm.

3. The low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, The N-ion doping concentration in the N-ion implantation region is 1×10⁻⁶. 18 -5×10 19 cm -3 The injection depth is 0.1-1μm.

4. The low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, The cathode electrode layer uses a Ti / Au electrode, and the anode electrode layer uses a Ni / Au electrode.

5. The low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, The field oxygen dielectric layer is made of alumina.

6. The low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, From a top-down perspective, the N-ion implantation region is a ring with an inner diameter of 50-60 μm and an outer diameter of 75-85 μm. The diameter of the anode electrode layer is 65-70 μm, and the length of the overlap region between the anode electrode layer and the field oxygen dielectric layer is 4-6 μm.

7. A method for fabricating a low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 1, characterized in that, Includes the following steps: (1) Clean the gallium oxide substrate, which includes a highly doped gallium oxide single crystal substrate layer and a low-doped gallium oxide single crystal epitaxial layer; (2) Growing a marker layer on the substrate; (3) N-ion implantation is performed in the low-doped gallium oxide single crystal epitaxial layer corresponding to the marker layer to form a box-shaped distribution using an ion implanter; (4) Annealing under a nitrogen atmosphere; (5) A cathode metal is grown on the back side of the gallium oxide substrate to form a cathode electrode layer; (6) Annealing in a nitrogen atmosphere to form an ohmic contact between the cathode metal and the substrate; (7) A field oxygen dielectric layer is grown on the surface of a gallium oxide substrate; (8) Anode metal is grown on the surface of the field oxygen dielectric layer to form an anode electrode layer.

8. The method for fabricating a low reverse leakage gallium oxide-based Schottky barrier diode according to claim 7, characterized in that, In step (3), three N-ion implantations are performed; the energy and dose of the first implantation are 45-55 keV, 5×10⁻⁶. 12 cm -3 The energy and dose of the second injection were 140-160 keV, 1×10⁻⁶. 13 cm -3 The energy and dose of the third injection were 220-240 keV, 2×10⁻⁶. 13 cm -3 .

9. The method for fabricating a low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 7, characterized in that, In step (4), the annealing temperature is 1080-1120℃ and the annealing time is 25-35 minutes; in step (6), the annealing temperature is 465-475℃ and the annealing time is 40s-80s.

10. The method for fabricating a low reverse leakage current gallium oxide-based Schottky barrier diode according to claim 7, characterized in that, In steps (5), (7) and (8), the growth method is electron beam evaporation; in step (7), the field oxygen dielectric layer is an alumina dielectric layer.

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