Gallium oxide surface treatment methods, semiconductor device fabrication processes, semiconductor devices

Abstract

This invention relates to gallium oxide surface treatment methods, semiconductor device processing techniques, and semiconductor devices in the field of semiconductor fabrication technology. The method pertains to reducing the surface defect density of gallium oxide. It involves treating the gallium oxide surface with argon ions, nitrogen ions, or helium ions to reconstruct the surface, followed by low-temperature oxygen atmosphere annealing (oxygen flow rate 0-100 sccm, annealing temperature 300-800℃, annealing time 0-24h) to fill oxygen vacancies on the surface, improving surface roughness and uniformity. This effectively suppresses leakage current and premature breakdown caused by fatal defects in gallium oxide, without increasing the specific on-resistance of the device. The device maintains good breakdown characteristics even at large-area scales, solving the technical problem that traditional gallium oxide samples can only effectively reduce the surface defect density by sacrificing the forward conduction loss of the device.

Description

Technical Field

[0001] This invention relates to a material surface treatment method in the field of semiconductor fabrication technology, and particularly to a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, a gallium oxide sample using the gallium oxide surface treatment method and a semiconductor device fabrication process, and a semiconductor device fabricated using the semiconductor device fabrication process. Background Technology

[0002] Gallium oxide (Ga2O3) is an ultra-wide bandgap semiconductor material with excellent properties such as high voltage withstand capability and radiation resistance, showing great application potential in high-power applications and extreme environmental conditions. In recent years, it has become a research hotspot in the field of electronic devices. In power electronic systems, gallium oxide power devices play key roles in rectification, clamping, freewheeling, and driving, and their current output capability, switching losses, conduction losses, and voltage withstand performance have received widespread attention. Currently, research has reported that small-area gallium oxide power devices (e.g., electrode radius < 500 μm or area < 1 mm²) have achieved ultra-high voltage withstand capabilities exceeding 10 kV. Although small-area devices have demonstrated the voltage withstand potential of gallium oxide, the high performance of large-area devices still faces significant challenges. Increasing the device area can improve current output capability and power level, but this leads to an increase in defects covering the electrodes, resulting in device performance degradation, especially a decrease in voltage withstand capability.

[0003] Currently, commercial gallium oxide epitaxial layers suffer from various killer defects, including line-shaped defects, polycrystals, nanoscale micro-trenches (NSGs), and thread defects (TDs). For gallium oxide power devices, the device surface typically needs to withstand a high electric field in reverse operation, and these surface defects lead to increased leakage current and premature breakdown. These defects originate from the epitaxial growth and fabrication process. On the one hand, adjusting the crystal orientation of the epitaxial layer during growth can suppress the formation of these defects, but this method reduces electron mobility. On the other hand, high-temperature (above 1100°C) oxygen annealing can also repair these defects, but it reduces the doping concentration of the gallium oxide epitaxial layer. Both methods increase the on-resistance of the device. Therefore, a more ideal approach is to develop a surface treatment technique that can effectively reduce the density of killer surface defects without sacrificing the forward conduction loss of the device. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] To address the technical problem that traditional gallium oxide samples can only effectively reduce the density of fatal surface defects by sacrificing the forward conduction loss of the device, this invention provides a gallium oxide surface treatment method for reducing the density of surface defects in gallium oxide, a gallium oxide sample using the gallium oxide surface treatment method and a semiconductor device fabrication process, and a semiconductor device fabricated using the semiconductor device fabrication process.

[0006] (2) Technical solution

[0007] In a first aspect, the present invention provides a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, comprising the following steps: bombarding the gallium oxide surface of a gallium oxide sample with an epitaxial layer with argon ions, or nitrogen ions, or helium ions; and annealing the gallium oxide surface after argon ion bombardment with low-temperature oxygen: the oxygen flow rate is 0-100 sccm, the annealing temperature is 300-800℃, and the annealing time is 0-24h.

[0008] As a further improvement to the above scheme, argon ions, nitrogen ions, and helium ions are all generated through an inductively coupled plasma system.

[0009] Furthermore, inductively coupled plasma systems include ICP-RIE, or PECVD and sputtering systems configured with ICP sources.

[0010] As a further improvement to the above scheme, the gallium oxide surface is cleaned with an organic solution and a piranha solution before argon ion bombardment.

[0011] As a further improvement to the above scheme, during argon ion bombardment, the gallium oxide sample is placed in an inductively coupled plasma system, with the system's ICP power set to 900W, RIE power to 300W, argon flow rate to 50 sccm, and argon ion bombardment time to 30 minutes.

[0012] As a further improvement to the above scheme, a rapid heat treatment system is used for low-temperature oxygen annealing. Pure oxygen is introduced during the heating and cooling processes of the rapid heat treatment system. The temperature is raised from room temperature to the maximum temperature of 400℃ at a rate of 20℃ / s, and the maximum temperature of 400℃ is maintained for 30 minutes.

[0013] Secondly, the present invention also provides a gallium oxide sample, wherein the gallium oxide surface of the gallium oxide sample is treated with the above-mentioned method for reducing the surface defect density of gallium oxide.

[0014] Thirdly, the present invention also provides a semiconductor device fabrication process, comprising: treating the gallium oxide surface of a gallium oxide sample with the above-mentioned gallium oxide surface treatment method for reducing the surface defect density of gallium oxide; and performing a semiconductor device fabrication process on the treated gallium oxide sample.

[0015] As a further improvement to the above scheme, the semiconductor device is a gallium oxide Schottky barrier diode, or a gallium oxide PN junction diode, or a gallium oxide metal-oxide semiconductor field-effect transistor, or a gallium oxide junction field-effect transistor, or a gallium oxide U-type metal-oxide semiconductor field-effect transistor.

[0016] Fourthly, the present invention also provides a semiconductor device, which is fabricated using any of the above-mentioned semiconductor device processing techniques.

[0017] (3) Beneficial effects

[0018] Compared with existing technologies, the gallium oxide surface treatment method of the present invention is a method for reducing the surface defect density of gallium oxide. By treating the gallium oxide surface with argon ions, nitrogen ions, or helium ions, the surface of gallium oxide is reconstructed. Then, low-temperature oxygen atmosphere annealing is performed to fill the oxygen vacancies on the surface, improving the surface roughness and uniformity. This can effectively suppress leakage and premature breakdown caused by fatal defects in gallium oxide, without increasing the specific on-resistance of the device. The device can still maintain good breakdown characteristics when the area is large. This solves the technical problem that traditional gallium oxide samples can only effectively reduce the surface fatal defect density by sacrificing the forward conduction loss of the device.

[0019] High-energy ion bombardment of semiconductor surfaces, such as with argon ions, is generally considered destructive or roughening. Engineers typically avoid high-energy argon ion treatment before device fabrication. However, in the large-area development of gallium oxide power devices, limitations due to fatal surface defects exist. This invention addresses this issue by bombarding gallium oxide samples with high-energy ions, such as argon ions, to rearrange gallium oxide atoms and eliminate these defects, thus preventing the sacrifice of forward conduction characteristics during defect repair. While low-temperature oxygen annealing has limited ability to repair fatal surface defects, this invention proactively introduces high-energy ion bombardment before annealing, creating a controllable layer of lattice damage and defects on the gallium oxide surface. The subsequent low-temperature oxygen annealing allows oxygen atoms to diffuse more effectively inward along the damaged areas and defect sites, achieving a deeper and more uniform passivation effect at a lower temperature. Without this pretreatment, low-temperature annealing may only be effective on the outermost layer. This ingenious combination effectively repairs fatal surface defects that cause leakage and premature device breakdown without increasing forward conduction losses. Attached Figure Description

[0020] Figure 1 A flowchart of a gallium oxide surface treatment method for reducing surface defect density in gallium oxide, provided in an embodiment of the present invention.

[0021] Figure 2For those that have not undergone surface treatment, using Figure 1 A comparison of fatal defects in two types of gallium oxide surfaces treated with Chinese methods, and between untreated Ref and surface-treated surfaces. Figure 1 A schematic diagram comparing the density of fatal defects on four types of gallium oxide surfaces with different RIE powers (50W, 100W, 300W) after surface treatment.

[0022] Figure 3 Comparison of roughness of gallium oxide epitaxial samples: without surface treatment (Ref), treated with argon ion at different RIE powers (50W, 100W, 300W), and after a second step of low-temperature oxygen annealing (OA).

[0023] Figure 4 To adopt Figure 1 A schematic diagram showing relevant information about gallium oxide Schottky barrier diodes from Chinese methods.

[0024] Figure 5 To adopt Figure 1 A comparison of relevant parameters between gallium oxide Schottky barrier diodes with different RIE powers (50W, 100W, 300W) processed by the Chinese method and existing gallium oxide Schottky barrier diodes. Detailed Implementation

[0025] 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.

[0026] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0027] Unless otherwise defined, 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 invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] Please see Figure 1This is a flowchart of a gallium oxide surface treatment method for reducing surface defect density in gallium oxide, provided in an embodiment of the present invention. The gallium oxide surface treatment method for reducing surface defect density employs a two-step process, and the material being treated can be gallium oxide material including different crystal planes (such as a gallium oxide sample with an epitaxial layer).

[0029] The first step involves using an argon ion bombardment method, specifically: bombarding the gallium oxide surface of the gallium oxide sample with an epitaxial layer with argon ions.

[0030] Besides argon ions, other plasmas with certain energy and density can be used to promote atomic migration on the gallium oxide surface, such as nitrogen ions and helium ions. Argon, nitrogen, and helium ions can all be generated using inductively coupled plasma (ICP) systems. ICP systems can be devices equipped with ICP sources; common devices with ICP sources include ICP-RIE, as well as certain PECVD and sputtering systems configured with ICP sources. Alternatively, traditional RIE devices capable of generating argon plasma, magnetron sputtering, and other techniques can also be used.

[0031] Before bombarding gallium oxide surfaces with argon ions, it is recommended to clean the gallium oxide surface first, such as by using organic solutions and piranha solutions to clean the gallium oxide surface.

[0032] The second step is to use low-temperature oxygen annealing, specifically: the gallium oxide surface bombarded by argon ions is treated with low-temperature oxygen annealing: the oxygen flow rate is 0-100 sccm, the annealing temperature is 300-800℃, and the annealing time is 0-24h.

[0033] Oxygen atmosphere annealing uses equipment including but not limited to rapid thermal processing (RTP) and conventional tube furnace annealing.

[0034] The gallium oxide surface is treated with argon ions of a certain energy and density to reconstruct the surface. Then, it is annealed in a low-temperature oxygen atmosphere to fill the oxygen vacancies on the surface and improve the surface roughness and uniformity.

[0035] This invention uses argon ions (Ar) +Argon ion bombardment and low-temperature oxygen annealing can avoid adverse effects on the carrier concentration and electron mobility of the gallium oxide substrate and epitaxial layer, while significantly reducing the density of fatal defects that cause additional leakage current and premature breakdown. When argon ions bombard the gallium oxide surface, the accumulated energy can promote the migration of atoms on the gallium oxide surface, thus reconstructing the gallium oxide surface without affecting the electrical properties of the underlying gallium oxide material, such as the carrier concentration and electron mobility. At this point, the reconstructed surface is relatively rough. Low-temperature oxygen annealing is then used to fill oxygen vacancies, reduce surface roughness, and improve the uniformity of the overall gallium oxide morphology. The two-step processing method proposed in this invention can greatly reduce fatal defects on the gallium oxide surface, promoting the application of high-voltage, high-power gallium oxide power devices.

[0036] Therefore, compared with the prior art, the present invention achieves the effect of reconstructing the gallium oxide surface by treating the gallium oxide surface with argon ions, nitrogen ions, or helium ions, followed by low-temperature oxygen atmosphere annealing to fill the oxygen vacancies on the surface and improve the surface roughness and uniformity. This can effectively suppress leakage and premature breakdown caused by fatal defects in gallium oxide, without increasing the specific on-resistance of the device. The device can still maintain good breakdown characteristics when the area is large. This solves the technical problem that traditional gallium oxide samples can only effectively reduce the density of fatal defects on the surface by sacrificing the forward conduction loss of the device.

[0037] Generally, gallium oxide samples can be treated with the gallium oxide surface treatment method of the present invention to reduce the surface defect density of gallium oxide. The gallium oxide surface treatment method of the present invention can also be applied to semiconductor device fabrication processes. For example, a semiconductor device fabrication process may include: treating the gallium oxide surface of a gallium oxide sample with the gallium oxide surface treatment method of the present invention; and then performing a semiconductor device fabrication process on the treated gallium oxide sample. The semiconductor device may be a gallium oxide Schottky barrier diode, a gallium oxide PN junction diode, a gallium oxide metal-oxide-semiconductor field-effect transistor (MOSFET), a gallium oxide junction field-effect transistor (JFET), or a gallium oxide U-type metal-oxide-semiconductor field-effect transistor (UMOSFET).

[0038] To better demonstrate the advantages of this invention over the prior art, specific experiments were conducted for comparative analysis. In this embodiment, a gallium oxide sample with an epitaxial layer is used as an example to illustrate the fabrication of a gallium oxide Schottky barrier diode. The fabrication method of the gallium oxide Schottky barrier diode includes: treating the gallium oxide surface of the gallium oxide sample using the method of reducing the surface defect density of gallium oxide in this embodiment; and then performing the fabrication process of the gallium oxide Schottky barrier diode on the treated gallium oxide sample.

[0039] For example, gallium oxide samples can first be cleaned with organic solvents and piranha solutions. Then, the gallium oxide samples can be placed horizontally in an inductively coupled plasma (ICP) system with the ICP power set to 900W, the RIE power to 300W, and the argon flow rate to 50 sccm. The sample surface is then treated under these conditions for 30 minutes.

[0040] Then, the gallium oxide sample treated with argon plasma can be placed in a rapid thermal processing (RTP) system, in which pure oxygen can be introduced during both heating and cooling processes. The maximum temperature can be raised from room temperature to 400°C at a rate of 20°C / s, and the maximum temperature can be maintained at 400°C for 30 minutes.

[0041] Finally, based on the gallium oxide samples processed in the above two steps, gallium oxide Schottky barrier diode devices are fabricated using standard process flow (including growth of back ohmic metal, ohmic metal annealing, preparation of edge termination structure, and growth of front anode metal).

[0042] This invention can effectively suppress leakage and premature breakdown caused by fatal defects in gallium oxide, without increasing the specific on-resistance of the device, and the device can still maintain good breakdown characteristics when the area is large.

[0043] Please combine Figure 2 , Figure 2 For those that have not undergone surface treatment, using Figure 1 A comparison of fatal defects in two types of gallium oxide surfaces treated by different methods, and between untreated Ref and surface-treated surfaces. Figure 1 A comparative schematic diagram showing the density of fatal defects on four types of gallium oxide surfaces treated by the method but with different RIE powers (50W, 100W, 300W). Figure 2 Confocal laser scanning microscopy images of gallium oxide epitaxial samples with dimensions of 5mm*7.5mm: (a) untreated and (b) treated (in an inductively coupled plasma system with an argon atmosphere and a RIE power of 300W). The treated samples show a significant reduction in fatal defects on the surface. (c) Comparison of fatal defect density between untreated and treated samples with different RIE powers (50W, 100W, 300W), showing a reduction of up to two orders of magnitude in defect density.

[0044] First, the gallium oxide sample with the epitaxial layer was treated with argon ions. To make the critical defects easier to observe, the untreated (Ref) and treated samples were immersed together in a potassium hydroxide solution. The microscopic observation results are as follows. Figure 2As shown in regions (a) and (b), the density of fatal defects on the gallium oxide surface significantly decreased after argon ion treatment. Statistical analysis showed that treating the sample with 300 W RIE power reduced the defect density by nearly two orders of magnitude compared to the untreated sample, demonstrating the superiority of this method. Figure 2 The region (c) is shown.

[0045] Compared to untreated samples, the roughness of samples treated with argon ions of different powers deteriorated, and the roughness increased further with increasing power. Subsequent low-temperature oxygen annealing in the second step restored the roughness of all samples treated with argon ions of different powers to a very low level, only 0.4–0.5 nm. Figure 3 As shown. Figure 3 A comparison of the roughness of gallium oxide epitaxial samples after argon ion treatment with different RIE powers (50W, 100W, 300W) and after a second step of low-temperature oxygen annealing (OA) showed that the roughness of the samples after argon ion treatment was significantly worse, while the roughness was greatly improved after the second step of low-temperature oxygen annealing.

[0046] Please combine Figure 4 , Figure 4 The diagram shows relevant information about gallium oxide epitaxial samples based on argon ion treatment and low-temperature oxygen annealing. (a) A cross-sectional view of the fabricated diode device, (b) A top view of the actual device structure, (c) A scanning electron microscope image of the edge termination structure, and (d) A comparison of the reverse breakdown characteristics of gallium oxide diode devices under untreated (w / o Ar plasma), Ar ion treated (w / Ar plasma), and high-temperature testing conditions (w / Ar plasma 450 K). Therefore, based on the gallium oxide epitaxial samples prepared by the two-step treatment method of argon ion treatment and low-temperature oxygen annealing, this embodiment fabricates a gallium oxide Schottky barrier diode with composite termination, as shown in the diagram. Figure 4 Region (a) is shown in the figure. In this embodiment, an electrode with a radius of 50 μm and an area of ​​9 mm² was fabricated on the same sample. 2 Two device sizes are presented, hereinafter referred to as small-area devices and large-area devices. Comparing the breakdown characteristics of untreated and two-step treated gallium oxide Schottky barrier diodes, the breakdown performance of the untreated large-area device degrades by as much as 68% compared to the small-area device. However, the breakdown performance of the treated large-area sample only degrades by 4%, demonstrating the effectiveness of the two-step treatment method in suppressing breakdown performance degradation when the device size increases. Meanwhile, thanks to the excellent electric field management efficiency of the composite termination, the large-area device can still maintain a breakdown voltage as high as 2kV. This large-area device achieves a leading international performance in currently reported research, such as... Figure 5 As shown, this invention differs from internationally reported large-area (≥1mm)2 Gallium oxide diode devices (Schottky barrier diode, SBD; junction barrier Schottky diode, JBS; heterojunction diode, HJD) were compared in terms of (a) output current-breakdown voltage and (b) specific on-resistance-breakdown voltage. The best device in this work is among the best in the world. It still maintains good withstand voltage and current output capability under high temperature 450k test conditions.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for reducing the surface defect density of gallium oxide, characterized in that, It includes the following steps: The gallium oxide surface of a gallium oxide sample with an epitaxial layer was bombarded with argon ions, nitrogen ions, or helium ions. The surface of gallium oxide bombarded by argon ions was treated with low-temperature oxygen annealing to fill the oxygen vacancies on the surface: the oxygen flow rate was 0-100 sccm, the annealing temperature was 300-800℃, and the annealing time was 0-24h.

2. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized in that, Argon ions, nitrogen ions, and helium ions are all generated through an inductively coupled plasma system.

3. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 2, characterized in that, Inductively coupled plasma systems include ICP-RIE, or PECVD and sputtering systems equipped with ICP sources.

4. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized in that, Before bombarding the gallium oxide surface with argon ions, the gallium oxide surface was cleaned with an organic solution and a piranha solution.

5. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized in that, During argon ion bombardment, the gallium oxide sample was placed in an inductively coupled plasma system. The system's ICP power was set to 900 W, RIE power to 300 W, argon flow rate to 50 sccm, and argon ion bombardment time to 30 minutes.

6. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized in that, Low-temperature oxygen annealing was performed using a rapid heat treatment system. Pure oxygen was introduced during both the heating and cooling processes of the rapid heat treatment system. The temperature was raised from room temperature to a maximum of 400°C at a rate of 20°C / s, and the maximum temperature of 400°C was maintained for 30 minutes.

7. A gallium oxide sample, characterized in that, The gallium oxide surface of the gallium oxide sample is treated with a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide as described in any one of claims 1 to 6.

8. A semiconductor device fabrication process, characterized in that, It includes: The gallium oxide surface of the gallium oxide sample is treated using the gallium oxide surface treatment method for reducing the surface defect density of gallium oxide as described in any one of claims 1 to 6; The process flow for fabricating semiconductor devices from the treated gallium oxide sample.

9. The semiconductor device fabrication process according to claim 8, characterized in that, The semiconductor device is a gallium oxide Schottky barrier diode, or a gallium oxide PN junction diode, or a gallium oxide metal-oxide semiconductor field-effect transistor, or a gallium oxide junction field-effect transistor, or a gallium oxide U-type metal-oxide semiconductor field-effect transistor.

10. A semiconductor device, characterized in that, The semiconductor device is fabricated using the semiconductor device fabrication process described in claim 8 or 9.

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