High voltage gallium oxide schottky diode with trench and metal ring composite termination structure

Abstract

The application relates to a high-voltage gallium oxide Schottky diode with a trench and metal ring combined terminal structure. The epitaxial layer of the gallium oxide SBD is etched at the anode edge to form a trench structure, and a metal ring is deposited in the trench to form a trench and metal ring combined terminal structure. The step-type terminal is used to cut off the electric field concentration point of the anode edge, the excess gallium oxide cations in the region are reduced, the peak electric field of the device is reduced from the root, the metal ring can better expand the depletion region, the electric field distribution is more uniform, the withstand voltage capacity and stability of the device are further improved, the same metal as the Schottky electrode of the device can be used, no additional process steps such as ion implantation are needed, the manufacturing process is simple, and the manufacturing cost of the device is reduced.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology, specifically relating to a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure. Background Technology

[0002] Mainstream silicon-based power devices suffer from low conversion efficiency and high power loss. Gallium oxide (GaO) power devices, with their high breakdown field strength and low power loss, have a promising market prospect in electronic power technology. In conventional GaO SBDs, an electric field concentration effect occurs at the anode apex. To improve the device's breakdown voltage, termination structures are needed to alleviate this electric field concentration effect. However, due to the current difficulty in p-type doping of GaO materials, it is challenging to address the crowding phenomenon using techniques such as junction termination extension and field-limiting rings. Currently, the mainstream termination structures available for GaO power devices include field plate structures, metal ring structures, and stepped structures. Among these, metal ring and stepped structures are relatively simple to fabricate. Stepped terminations use a truncation method to cut off the electric field concentration point at the anode edge, reducing excess GaO cations in that region and fundamentally reducing the peak electric field of the device. The addition of a metal ring can better extend the depletion region, further improving the device's breakdown voltage capability. Furthermore, it can use the same metal as the device's Schottky electrode, eliminating the need for additional processing steps such as ion implantation. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned problems by providing a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure. This eliminates the need for ion implantation and simplifies the process steps, enabling its effective application in industrial production. It also alleviates electric field congestion in the termination region, improves the electric field distribution, and further enhances the voltage withstand performance and reliability of the gallium oxide SBD device.

[0004] To achieve the above objectives, the technical solution of the present invention is: a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure, the structure of which is as follows: Figure 1As shown, a gallium oxide Schottky barrier diode comprises, from bottom to top, a cathode metal layer 1, a highly doped N-type gallium oxide substrate 2, a lightly doped N-type gallium oxide epitaxial layer 3, an oxide dielectric layer 4, an anode metal layer 5, and metal rings 6. The highly doped N-type gallium oxide substrate 2 is disposed on top of the cathode metal layer 1. The lightly doped N-type gallium oxide epitaxial layer 3 is disposed on top of the highly doped N-type gallium oxide substrate 2. The anode metal layer 5 is disposed at the middle of the top of the lightly doped N-type gallium oxide epitaxial layer 3. The edges of the anode metal layer 5 are etched to form a trench mesa with a certain width and depth. The oxide dielectric layer 4 covers the trench mesa and the trench sidewalls. Several metal rings 6 are evenly placed in the trench mesa and pass through the oxide dielectric layer 4 to contact the lightly doped N-type gallium oxide epitaxial layer 3, and are recessed to a certain depth in the lightly doped N-type gallium oxide epitaxial layer 3.

[0005] In one embodiment of the present invention, the oxide dielectric layer 4 is made of oxides such as HfO2, Al2O3, and SiO2, and the thickness of the dielectric layer 4 is 50nm~3μm.

[0006] In one embodiment of the present invention, the anode metal layer 5 may be made of the following materials: metals such as Au, Ni, Pt and TiN.

[0007] In one embodiment of the present invention, the metal ring 6 can be selected from metals such as Au, Ni, Pt and TiN; the thickness of the metal ring 6 is 0.2~2.1μm, the recess depth is 0.1~2μm, the length is 1~8μm, the ring spacing of the metal ring is 0.5~3μm, and the number of metal rings M can be selected according to product requirements.

[0008] In one embodiment of the present invention, the cathode metal layer 1 may be made of Ti or Au.

[0009] In one embodiment of the present invention, the highly doped N-type gallium oxide substrate 2 has a thickness of 500~650 μm and a doping concentration of 10. 18 ~10 20 cm -3 Gallium oxide materials.

[0010] In one embodiment of the present invention, the thickness of the low-doped N-type gallium oxide epitaxial layer 3 is 5~20 μm, and the doping concentration is 10. 15 ~10 17 cm -3 Gallium oxide materials.

[0011] In one embodiment of the present invention, the etching depth of the trench structure in the terminal region of the low-doped N-type gallium oxide epitaxial layer 3 is 1~5μm.

[0012] This invention discloses a method for fabricating a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure, comprising: Step 1: Using hydride vapor phase epitaxy (HVPE) or metal-organic chemical vapor deposition (MOCVD) processes, grow a lightly doped N-type gallium oxide epitaxial layer 3 on top of a highly doped N-type gallium oxide substrate 2. Step 2: Spin-coat photoresist on the surface of the low-doped N-type gallium oxide epitaxial layer 3, form the trench opening pattern of the terminal area using standard photolithography, and etch the low-doped N-type gallium oxide epitaxial layer 3 using reactive ion etching to form a groove for depositing the metal ring 6. Step 3: An oxide dielectric layer 4 is grown on the lightly doped N-type gallium oxide epitaxial layer 3 using atomic layer deposition technology; Step 4: Spin-coat photoresist onto oxide dielectric layer 4, and form the opening pattern of anode metal 5 and metal ring 6 using standard photolithography process; Step 5: Based on the opening pattern of the anode metal 5 and the metal ring 6, the oxide dielectric layer 4 is etched using reactive ion etching process, etching down to the low-doped N-type gallium oxide epitaxial layer 3 and then etching down to a certain depth. Step 6: Based on the opening pattern, deposit metal on the lightly doped N-type gallium oxide epitaxial layer 3 using processes including magnetron sputtering or electron beam evaporation to form the anode metal 5 and the metal ring structure 6. Simultaneously, deposit the cathode metal 1 on the bottom of the heavily doped N-type gallium oxide substrate 2.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a new high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure. Without the need for additional processes such as ion implantation, and with the metal ring and metal anode being formed simultaneously, the process is simple, yet the effect is very significant. It optimizes the electric field distribution of the gallium oxide SBD device, enabling the gallium oxide SBD device to obtain a stable high breakdown voltage. Due to the simple fabrication process, the number of masks is greatly reduced, further reducing the cost of device fabrication. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a high-voltage gallium oxide Schottky diode structure with a trench and metal ring composite terminal structure according to a preferred embodiment of the present invention; Figures 2-6 This is a detailed process fabrication diagram of a high-voltage gallium oxide Schottky diode with a trench and metal ring composite terminal structure according to a preferred embodiment of the present invention; Figure 7 This diagram illustrates the voltage withstand relationship between a high-voltage gallium oxide Schottky diode with a trench and metal ring composite terminal structure and a gallium oxide Schottky barrier diode without a trench metal ring structure, according to a preferred embodiment of the present invention, under the same conditions. Detailed Implementation

[0015] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0017] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0018] This invention discloses a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure, the structure of which is as follows: Figure 1 As shown, a gallium oxide Schottky barrier diode includes a cathode metal layer 1, a highly doped N-type gallium oxide substrate 2, a lightly doped N-type gallium oxide epitaxial layer 3, an oxide dielectric layer 4, an anode metal layer 5, and several metal rings 6. The cathode metal layer 1 is deposited below the highly doped N-type gallium oxide substrate 2, forming an ohmic contact with it, and serves as the cathode of the gallium oxide Schottky barrier diode. The cathode metal layer 1 is made of Ti. The highly doped N-type gallium oxide substrate 2 has a thickness of 300~650 μm and a doping concentration of 10%. 18 ~10 20 cm -3 The material is gallium oxide. The low-doped N-type gallium oxide epitaxial layer 3 is disposed on top of the high-doped N-type gallium oxide substrate 2; the thickness of the low-doped N-type gallium oxide epitaxial layer 3 is 5~20μm, and the doping concentration is 10. 15 ~10 17 cm -3The material is gallium oxide. The anode metal layer 5 is disposed at the top center of the lightly doped N-type gallium oxide epitaxial layer 3; the edge of the anode metal layer 5 is etched to form a trench mesa with a certain width and depth; the etching depth of the trench structure in the terminal region of the lightly doped N-type gallium oxide epitaxial layer 3 is 1~5μm. The oxide dielectric layer 4 covers the trench mesa and the trench sidewalls; the oxide dielectric layer 4 is made of oxides such as HfO2, Al2O3, and SiO2. The plurality of metal rings 6 are uniformly placed in the trench platform and pass through the oxide dielectric layer 4 to contact the lightly doped N-type gallium oxide epitaxial layer 3, and are recessed to a certain depth in the lightly doped N-type gallium oxide epitaxial layer 3; the anode metal layer 5 and the metal rings 6 can be metals such as Au, Ni, Pt and TiN; the thickness of the metal rings 6 is 0.2~2.1μm, the recess depth is 0.1~2μm, the length is 1~8μm, the spacing between the metal rings is 0.5~3μm, and the number of metal rings M can be selected according to product requirements.

[0019] Reference Figures 2-6 This invention fabricates a high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure, and the following embodiments are provided: In this embodiment, the thickness of the dielectric layer HfO2 is 100 nm, the trench depth is 3 μm, the length of the metal ring is 5 μm, the number of metal rings is 12, the metal ring depression is 1 μm, and the inter-ring spacing of the metal rings is 0.75 μm.

[0020] (1) A 500 μm thick material with a doping concentration of 5.9 × 10⁻⁶ 18 cm -3 The highly doped N-type gallium oxide substrate 2 was sequentially ultrasonically cleaned with acetone solution, ethanol and deionized water for 5-15 minutes. The cleaned highly doped N-type gallium oxide substrate 2 was then dried with nitrogen gas. After that, the cleaned and dried highly doped N-type gallium oxide substrate 2 was heat-treated to remove surface contaminants.

[0021] (2) A cathode metal layer 1 is deposited on the bottom of a highly doped N-type gallium oxide substrate 2 by magnetron sputtering.

[0022] (3) The epitaxial growth thickness is 20 μm using HVPE or MOCVD process, and the concentration is 8.5 × 10⁻⁶. 15 cm -3 3. Low-doped N-type gallium oxide epitaxial layer.

[0023] (4) A groove pattern is formed on the upper surface of the epitaxial layer by photolithography, and the photolithographic sample is placed in a reactive ion etching system for etching to form a groove with an etching depth of 4 μm.

[0024] (5) Remove the photoresist from the sample after trench etching and place it in an atomic layer deposition system to grow a 100 nm HfO2 dielectric layer 4.

[0025] (6) Anode metal pattern and metal ring pattern are formed on the upper surface of HfO2 dielectric layer 4 by photolithography. The HfO2 dielectric layer 4 is etched by reactive ion etching according to the anode metal and metal ring opening pattern until the upper surface of the low-doped N-type gallium oxide epitaxial layer 3 is reached. Then the surface is cleaned and the low-doped N-type gallium oxide epitaxial layer 3 is etched by reactive ion etching for 1 μm. Then the surface is cleaned. Metal is deposited on the low-doped N-type gallium oxide epitaxial layer 3 by evaporation or sputtering to form anode metal 5 and 12 metal rings 6 of 5 μm each.

[0026] Working principle of this invention: This invention combines a stepped termination structure and a metal ring termination structure. The stepped termination uses a truncation method to cut off the electric field concentration point at the anode edge, reducing excess gallium oxide cations in this region and fundamentally reducing the peak electric field of the device. The addition of the metal ring can better expand the depletion region, further improving the device's breakdown voltage capability. Furthermore, it can use the same metal as the device's Schottky electrode, eliminating the need for additional process steps such as ion implantation. The combination of these two termination structures results in a more uniform electric field distribution. Therefore, the device proposed in this invention can optimize the electric field distribution while reducing manufacturing costs, thereby significantly improving the device's breakdown voltage performance.

[0027] Figure 7 This paper presents a comparison of the breakdown voltage of a gallium oxide Schottky barrier diode with a trench and metal ring composite termination structure (M=12 metal rings) using a 100nm thick HfO2 dielectric layer as the dielectric layer, an etched trench depth of 3μm, a metal ring length of 5μm, a recess depth of 1μm, a metal ring spacing of 0.75μm, and a trench and metal ring composite termination structure, compared with that of a gallium oxide Schottky barrier diode without a termination structure under the same conditions. Figure 7 As can be seen, the breakdown voltage of the gallium oxide Schottky barrier diode without a termination structure is only 965V. The breakdown voltage of the gallium oxide Schottky barrier diode with a trench and metal ring composite termination structure reaches 6651V. With other parameters remaining constant, the gallium oxide Schottky barrier diode with the trench and metal ring composite termination structure achieves a 589% improvement compared to the gallium oxide Schottky barrier diode without a termination structure, significantly increasing the breakdown voltage of the gallium oxide Schottky barrier diode.

[0028] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure, characterized in that, include: Cathode metal layer (1), highly doped N-type gallium oxide substrate (2), low doped N-type gallium oxide epitaxial layer (3), oxide dielectric layer (4), anode metal layer (5), and several metal rings (6). The highly doped N-type gallium oxide substrate (2) is disposed on top of the cathode metal layer (1); The low-doped N-type gallium oxide epitaxial layer (3) is disposed on top of the high-doped N-type gallium oxide substrate (2); The anode metal layer (5) is disposed on top of the lightly doped N-type gallium oxide epitaxial layer (3); The edges of the anode metal layer (5) and the low-doped N-type gallium oxide epitaxial layer (3) are etched to form a trench mesa with a predetermined width and depth, and trench sidewalls are formed. The oxide dielectric layer (4) covers the trench platform and the trench sidewall; The plurality of metal rings (6) are uniformly placed in the trench mesa and pass through the oxide dielectric layer (4) to contact the low-doped N-type gallium oxide epitaxial layer (3), and are recessed to a predetermined depth in the low-doped N-type gallium oxide epitaxial layer (3).

2. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The oxide dielectric layer (4) is made of oxides including HfO2, SiO2 or Al2O3, and the thickness of the dielectric layer is 50nm~3μm.

3. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The anode metal layer (5) is made of a metal material including Au, Ni or Pt.

4. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The metal rings (6) are selected from metals including Au, Ni or Pt, with a thickness of 0.2~3.1μm, a recess depth of 0.1~3μm, a length of 1~8μm, a ring spacing of 0.5~3μm, and the number of metal rings M is selected according to product requirements.

5. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The cathode metal layer (1) is made of a metal material including Ti or Au.

6. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The high-doped N-type gallium oxide substrate (2) has a thickness of 500-650 μm and a gallium oxide material with a doping concentration of 10 18 ~10 20 cm -3 .

7. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The thickness of the lightly doped N-type gallium oxide epitaxial layer (3) is 5~20 μm, and the doping concentration is 10. 15 ~10 17 cm -3 Gallium oxide materials.

8. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The etching depth of the anode edge trench structure of the low-doped N-type gallium oxide epitaxial layer (3) is 1~5μm.

9. The high-voltage gallium oxide Schottky diode with a trench and metal ring composite termination structure according to claim 1, characterized in that, The diode fabrication method includes the following steps: Step 1: Using hydride vapor phase epitaxy (HVPE) or metal-organic chemical vapor deposition (MOCVD) processes, a low-doped N-type gallium oxide epitaxial layer (3) is epitaxially grown on the top of a highly doped N-type gallium oxide substrate (2). Step 2: Spin-coat photoresist on the surface of the low-doped N-type gallium oxide epitaxial layer (3), form the trench opening pattern of the terminal area using standard photolithography, and etch the low-doped N-type gallium oxide epitaxial layer (3) using reactive ion etching to form a groove for depositing the metal ring (6). Step 3: An oxide dielectric layer (4) is grown on the low-doped N-type gallium oxide epitaxial layer (3) using atomic layer deposition technology. Step 4: Spin-coat photoresist onto the oxide dielectric layer (4) and form the opening pattern of the anode metal layer (5) and the metal ring (6) using standard photolithography process; Step 5: According to the opening pattern of the anode metal layer (5) and the metal ring (6), the oxide dielectric layer (4) is etched using reactive ion etching process, etched to the low-doped N-type gallium oxide epitaxial layer (3) and etched down to a predetermined depth; Step 6: According to the opening pattern, metal is deposited on the low-doped N-type gallium oxide epitaxial layer (3) using processes including magnetron sputtering or electron beam evaporation to form an anode metal layer (5) and a metal ring (6); at the same time, a cathode metal layer (1) is deposited at the bottom of the high-doped N-type gallium oxide substrate (2).

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