Gallium oxide surface treatment method, semiconductor device processing technology and semiconductor device

Abstract

The invention relates to a gallium oxide surface treatment method, a semiconductor device processing technology and a semiconductor device in the technical field of semiconductor manufacturing. The method belongs to a method for reducing the surface defect density of gallium oxide, the surface of gallium oxide is treated by argon ions, nitrogen ions or helium ions to achieve the effect of reconstructing the surface of gallium oxide, then low-temperature oxygen atmosphere annealing (the oxygen flow is 0-100 sccm, the annealing temperature is 300-800 DEG C, and the annealing time is 0-24 h) is carried out, oxygen vacancies on the surface are filled, and the defect density of the surface of gallium oxide is reduced. The problems of surface roughness and uniformity are improved, so that the problems of electric leakage and advanced breakdown caused by a fatal defect of gallium oxide can be effectively inhibited, meanwhile, the specific on-resistance of the device is not increased, and the device can still maintain good breakdown characteristics in a large area. The technical problem that the surface fatal defect density of a traditional gallium oxide sample can be effectively reduced only by sacrificing the forward conduction loss of a device is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and particularly relates to a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, a gallium oxide sample adopting the gallium oxide surface treatment method, a semiconductor device processing technology adopting the gallium oxide surface treatment method, and a semiconductor device prepared by adopting the semiconductor device processing technology. BACKGROUND

[0002] Gallium oxide (Ga2O3) is an ultra-wide bandgap semiconductor material with high voltage resistance, radiation resistance and other excellent properties, and has 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. Their current output capability, switching loss, conduction loss and voltage resistance performance are widely concerned. At present, small-area gallium oxide power devices (such as electrode radius < 500 μm or area < 1 mm²) reported by research have achieved an ultra-high voltage resistance of more than 10 kV. Although small-area devices have shown the voltage resistance potential of gallium oxide material, the high performance of large-area devices still faces significant challenges. Increasing the device area can improve the current output capability and power level, but the defects covered under the electrode increase, leading to degradation of device performance, especially the decrease of voltage resistance.

[0003] At present, there are various killer defects on the commercial gallium oxide epitaxial layer, including line-shaped defects, polycrystals, nanoscale-microgroove (NSG), thread defects (TD), etc. For gallium oxide power devices, the device surface usually needs to withstand a high electric field in the reverse working state. These surface defects can cause increased leakage and premature breakdown. These defects are derived from the epitaxial growth and epitaxial processing. On the one hand, by adjusting the crystal orientation of the epitaxial layer, the generation of such defects can be inhibited, but this method will reduce the electron mobility. On the other hand, high-temperature (above 1100℃) oxygen annealing can also repair these defects, but it will reduce the doping concentration of the gallium oxide epitaxial layer. Both methods will increase the on-resistance of the device. Therefore, a more ideal method is to develop a surface treatment technology that can effectively reduce the surface killer defect density without sacrificing the forward conduction loss of the device. SUMMARY

[0004] (1) Technical problems to be solved In order to solve the technical problem that the conventional gallium oxide sample can only reduce the surface fatal defect density by sacrificing the forward conduction loss of the device, the application provides a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, a gallium oxide sample and a semiconductor device processing technology adopting the gallium oxide surface treatment method, and a semiconductor device prepared by adopting the semiconductor device processing technology.

[0005] (2) Technical scheme In a first aspect, the application provides a gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, which comprises the following steps: bombarding the gallium oxide surface of a gallium oxide sample with an epitaxial layer by using argon ions, nitrogen ions or helium ions; and treating the gallium oxide surface bombarded by the argon ions by low-temperature oxygen annealing, wherein the oxygen flow rate is 0-100 sccm, the annealing temperature is 300-800 DEG C, and the annealing time is 0-24 h.

[0006] As a further improvement of the above-mentioned scheme, the argon ions, nitrogen ions and helium ions are generated by an inductively coupled plasma system.

[0007] Further, the inductively coupled plasma system comprises an ICP-RIE, or a PECVD and a sputtering system configured with an ICP source.

[0008] As a further improvement of the above-mentioned scheme, before bombarding the gallium oxide surface by the argon ions, the gallium oxide surface is cleaned by using an organic solution and an aiptasia solution.

[0009] As a further improvement of the above-mentioned scheme, when the gallium oxide sample is bombarded by the argon ions, the gallium oxide sample is placed in the inductively coupled plasma system, the ICP power of the system is set to 900 W, the RIE power is set to 300 W, the argon flow rate is set to 50 sccm, and the argon ion bombardment time is set to 30 minutes.

[0010] As a further improvement of the above-mentioned scheme, the low-temperature oxygen annealing is performed by using a rapid thermal treatment system, pure oxygen is introduced during the heating and cooling processes of the rapid thermal treatment system, the temperature is increased from room temperature to a maximum temperature of 400 DEG C at a rate of 20 DEG C / s, and the maximum temperature of 400 DEG C is maintained for 30 minutes.

[0011] In a second aspect, the application further provides a gallium oxide sample, wherein the gallium oxide surface of the gallium oxide sample is treated by using any of the above-mentioned methods for reducing the surface defect density of gallium oxide.

[0012] In a third aspect, the application further provides a semiconductor device processing technology, which comprises: treating the gallium oxide surface of a gallium oxide sample by using any of the above-mentioned gallium oxide surface treatment methods for reducing the surface defect density of gallium oxide; and performing a semiconductor device preparation process on the treated gallium oxide sample.

[0013] As a further improvement of the above-mentioned solution, 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-shaped metal-oxide-semiconductor field effect transistor.

[0014] In a fourth aspect, the present application also provides a semiconductor device, which is prepared by using the processing technology of any of the above-mentioned semiconductor devices.

[0015] (3) Advantages Compared with the prior art, the gallium oxide surface treatment method of the present application is a method for reducing the surface defect density of gallium oxide. By treating the surface of gallium oxide with argon ions, or nitrogen ions, or helium ions, the surface of gallium oxide is restructured, and then low-temperature oxygen atmosphere annealing is performed to fill the surface oxygen vacancies and improve the surface roughness and uniformity, thereby effectively inhibiting the leakage and premature breakdown caused by the fatal defects of gallium oxide, without increasing the specific on-resistance of the device. The device can still maintain good breakdown characteristics when it is large in size, and the technical problem of the prior art that the surface fatal defect density of the traditional gallium oxide sample can only be effectively reduced by sacrificing the forward conduction loss of the device is solved.

[0016] High-energy ion bombardment on the surface of a semiconductor, such as argon ions, is generally considered to be destructive or roughening to the surface. Generally, any engineer would avoid high-energy argon ion treatment on the surface before device preparation as much as possible. However, in the process of large-area gallium oxide power devices, limited by surface fatal defects, in order to avoid sacrificing the forward conduction characteristics when repairing the surface fatal defects, the present application uses high-energy ion bombardment, such as argon ions, on the surface of the gallium oxide sample to rearrange the gallium oxide atoms and eliminate the surface fatal defects. Low-temperature oxygen annealing has limited ability to repair surface fatal defects. The present application actively introduces high-energy ion bombardment before annealing to introduce a controllable lattice damage and defect layer on the surface of gallium oxide, and then performs low-temperature oxygen annealing treatment. Oxygen atoms can more effectively diffuse inward along the damage area and defect sites, thereby achieving a deeper and more uniform passivation effect at a lower temperature. Without this pretreatment, low-temperature annealing may only be effective for the topmost layer. Through the delicate combination of the two, the surface fatal defects that cause leakage and lead to premature breakdown of the device can be repaired, and the increase in forward conduction loss can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide provided for the embodiments of the present application is shown in the flowchart.

[0018] Figure 2 The gallium oxide sample has not been subjected to surface treatment and is prepared by using the gallium oxide surface treatment method for reducing the surface defect density of gallium oxide provided for the embodiments of the present application. Figure 1The fatal defect comparison of two types of gallium oxide surfaces treated by surface method and the untreated Ref, the four types of gallium oxide surfaces treated by surface method but different RIE power (50W, 100W, 300W). Figure 1 The fatal defect density comparison of four types of gallium oxide surfaces treated by surface method but different RIE power (50W, 100W, 300W).

[0019] Figure 3 The roughness comparison of gallium oxide epitaxial samples untreated Ref, treated by different RIE power (50W, 100W, 300W) and treated by second step of low temperature oxygen annealing (OA).

[0020] Figure 4 The related information of gallium oxide Schottky barrier diode treated by surface method. Figure 1 The related information of gallium oxide Schottky barrier diode treated by surface method.

[0021] Figure 5 The related information of gallium oxide Schottky barrier diode treated by surface method. Figure 1 The related parameter comparison of gallium oxide Schottky barrier diode treated by surface method but different RIE power (50W, 100W, 300W) and the existing gallium oxide Schottky barrier diode. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0023] It should be noted that when a component is referred to as being "mounted on" another component, it can be directly on the other component or there can be a middle component. When a component is referred to as being "disposed on" another component, it can be directly disposed on the other component or there can be a middle component. When a component is referred to as being "fixed on" another component, it can be directly fixed on the other component or there can be a middle component.

[0024] 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 application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0025] Please refer to Figure 1A flow chart of the gallium oxide surface treatment method for reducing the surface defect density of gallium oxide is provided for the embodiments of the present application. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide adopts a two-step treatment method, and the material to be treated can be gallium oxide material including different crystal faces (such as gallium oxide samples with an epitaxial layer).

[0026] In the first step, an argon ion bombardment treatment method is adopted, specifically: the gallium oxide surface of the gallium oxide sample with an epitaxial layer is bombarded with argon ions.

[0027] In addition to argon ions, other plasmas with certain energy and density can also be used to promote the atomic migration of the gallium oxide surface, such as nitrogen ions, helium ions, etc. Argon ions, nitrogen ions, and helium ions can be generated by an inductively coupled plasma system (ICP). The inductively coupled plasma system can be a device with an ICP source. Common devices with an ICP source can include ICP-RIE, and some PECVD and sputtering systems configured with an ICP source. In addition, traditional RIE devices that can generate argon plasma, magnetron sputtering, and other technologies can also be used.

[0028] Before bombarding the gallium oxide surface with argon ions, it is recommended to clean the gallium oxide surface first, such as using organic solution and piranha solution to clean the gallium oxide surface.

[0029] In the second step, low-temperature oxygen annealing is adopted, specifically: the gallium oxide surface after argon ion bombardment is treated by low-temperature oxygen annealing: the oxygen flow is 0-100 sccm, the annealing temperature is 300-800℃, and the annealing time is 0-24h.

[0030] The equipment used for oxygen atmosphere annealing includes but is not limited to rapid thermal processing (RTP), and traditional tube furnace annealing.

[0031] The gallium oxide surface is treated with argon ions with certain energy and density to achieve the effect of restructuring the gallium oxide surface, and then low-temperature oxygen atmosphere annealing is performed to fill the surface oxygen vacancies and improve the surface roughness and uniformity.

[0032] The present application adopts argon ions (Ar +) processing and low-temperature oxygen annealing, the carrier concentration and electron mobility of the gallium oxide substrate and the epitaxial layer can be avoided from being adversely affected, and the fatal defect density causing additional leakage and premature breakdown can be greatly reduced. When the gallium oxide surface is bombarded by argon ions, the accumulated energy can promote the migration of atoms on the surface of the gallium oxide, thereby reconstructing the surface of the gallium oxide, but without affecting the carrier concentration, electron mobility and other electrical properties of the gallium oxide material below the surface. At this time, the reconstructed surface is relatively rough, and at this time, low-temperature oxygen annealing is used to fill oxygen vacancies and reduce surface roughness, thereby improving the uniformity of the entire gallium oxide morphology. The two-step processing method proposed in the present application can greatly reduce the fatal defects on the surface of the gallium oxide, thereby promoting the application process of high-voltage, high-power gallium oxide power devices.

[0033] Therefore, compared with the prior art, the present application can effectively inhibit the leakage and premature breakdown caused by the fatal defects of the gallium oxide by using argon ions, or nitrogen ions, or helium ions to treat the surface of the gallium oxide, thereby achieving the effect of reconstructing the surface of the gallium oxide, and then performing low-temperature oxygen annealing to fill the surface oxygen vacancies, improve the surface roughness and uniformity, thereby effectively inhibiting the leakage and premature breakdown caused by the fatal defects of the gallium oxide, without increasing the specific on-resistance of the device, and the device can still maintain good breakdown characteristics when it is large-sized, thereby solving the technical problem that the conventional gallium oxide sample can only sacrifice the forward conduction loss of the device to effectively reduce the surface fatal defect density.

[0034] In general, the gallium oxide sample can be treated by the gallium oxide surface defect density reduction method of the present application. The gallium oxide surface defect density reduction method of the present application can also be applied to the processing technology of semiconductor devices, such as the processing technology of semiconductor devices, which can include: treating the gallium oxide surface of the gallium oxide sample by the gallium oxide surface defect density reduction method of the present application; and performing the preparation process of the semiconductor device on the treated gallium oxide sample. The semiconductor device can be a gallium oxide Schottky barrier diode, or a gallium oxide PN junction diode, or a gallium oxide metal-oxide semiconductor field effect transistor (MOSFET), or a gallium oxide junction field effect transistor (JFET), or a gallium oxide U-shaped metal-oxide semiconductor field effect transistor (UMOSFET).

[0035] In order to better demonstrate the advantages of the present application over the prior art, specific experiments are also conducted for comparison and demonstration. In this embodiment, the gallium oxide sample with an epitaxial layer is taken as an example to illustrate the preparation of a gallium oxide Schottky barrier diode. The preparation method of the gallium oxide Schottky barrier diode includes: treating the gallium oxide surface of the gallium oxide sample by the gallium oxide surface defect density reduction method of the present embodiment; and performing the preparation process of the gallium oxide Schottky barrier diode on the treated gallium oxide sample.

[0036] For example, first, the gallium oxide sample can be cleaned with an organic solution and an arapaima solution, then the gallium oxide sample can be placed horizontally in an inductively coupled plasma system (ICP), the ICP power of the system is set to 900W, the RIE power is set to 300W, the argon flow is set to 50sccm, the sample surface is processed under the above conditions, and the processing time is 30 minutes.

[0037] Then, the gallium oxide sample treated by argon plasma can be placed in a rapid thermal processing (RTP) system, pure oxygen can be introduced during the heating and cooling processes, the temperature can be raised to 400℃ from room temperature, the heating rate can be 20℃ / s, the highest temperature can be maintained for 30 minutes.

[0038] Finally, based on the gallium oxide sample processed by the above two steps, a gallium oxide Schottky barrier diode device is prepared by a standard process flow (including growing back ohmic metal, ohmic metal annealing, preparing edge termination structure, growing front anode metal).

[0039] The present application can effectively suppress the leakage and premature breakdown problems caused by the fatal defects of gallium oxide, without increasing the specific on-resistance of the device, and the device can still maintain good breakdown characteristics when large-sized.

[0040] Please refer to Figure 2 , Figure 2 The fatal defects of two types of gallium oxide surfaces that have not been surface treated and treated by the method of the present application are compared, and the fatal defect densities of four types of gallium oxide surfaces that have not been surface treated and treated by the method of the present application but have different RIE powers (50W, 100W, 300W) are compared. Figure 1 The fatal defect densities of four types of gallium oxide surfaces that have not been surface treated and treated by the method of the present application but have different RIE powers (50W, 100W, 300W) are compared. Figure 1 The confocal laser scanning microscope images of the gallium oxide epitaxial samples with a size of 5mm*7.5mm (a) untreated and (b) treated (in an inductively coupled plasma system, under the condition of RIE power of 300W in argon atmosphere) are shown, and the fatal defects on the surface of the treated sample are obviously reduced; (c) the fatal defect densities of untreated and treated by different RIE powers (50W, 100W, 300W) are compared, and the defect density can be reduced by two orders of magnitude at most. Figure 2 First, the gallium oxide sample with an epitaxial layer is treated by argon ion, in order to make the fatal defects more easily observed, the untreated (Ref) and the treated sample are soaked in potassium hydroxide solution together, and the microscope observation results are as follows

[0041] Figure 2 ​(a), (b), after argon ion treatment, the fatal defect density of the gallium oxide surface is significantly reduced, through statistics, compared with the untreated sample, the defect density of the sample treated by 300 W RIE power is reduced by nearly two orders of magnitude, which embodies the superiority of the method, as shown in Figure 2 region (c).

[0042] After argon ion treatment with different power, the roughness of the sample relative to the untreated sample is deteriorated, and with the increase of the power, the roughness is further increased, and then the second step of low temperature oxygen annealing is adopted, and the roughness of the sample treated by argon ion with different power is returned to a very low level, only 0.4-0.5 nm, as shown in Figure 3 . Figure 3 After argon ion treatment with different RIE power (50W, 100W, 300W) and after the second step of low temperature oxygen annealing (OA), the roughness of the gallium oxide epitaxial sample is compared, the roughness of the sample treated by argon ion is obviously deteriorated, and the roughness is greatly improved after the second step of low temperature oxygen annealing.

[0043] Please refer to Figure 4 , Figure 4 is a schematic diagram of the related information of the gallium oxide epitaxial sample based on the two steps of argon ion treatment and low temperature oxygen annealing, (a) is a schematic diagram of the cross section of the prepared diode device, (b) is a top view of the actual device structure, (c) is a scanning electron microscope diagram of the edge terminal structure, (d) is a comparison of the reverse breakdown characteristics of the gallium oxide diode device under the conditions of untreated (w / o Ar plasma) and Ar ion treatment (w / Ar plasma) and high temperature test (w / Ar plasma 450 k). Therefore, based on the gallium oxide epitaxial sample treated by the two steps of argon ion treatment and low temperature oxygen annealing, a gallium oxide Schottky barrier diode with a composite terminal is prepared in the embodiment, and the structure is as shown in Figure 4 region (a) in the figure. In the embodiment, two devices with electrode radius of 50μm and area of 9mm 2 are prepared on the same sample, which are referred to as small area device and large area device below. By comparing the breakdown characteristics of the untreated and two-step treated gallium oxide Schottky barrier diode devices, the breakdown performance of the large area device is degraded by 68% compared with the small area device, but the breakdown performance of the treated sample is only degraded by 4%, which embodies the effectiveness of the two-step treatment method in inhibiting the degradation of the breakdown performance of the large area device. At the same time, thanks to the good electric field management efficiency of the composite terminal, the breakdown voltage of the large area device can still reach 2kV. The comprehensive performance of the large area device reaches the international leading position in the research work reported in the world, as shown in Figure 5 , the large area (≥1mm2 ) Oxide gallium diode devices (Schottky barrier diode, SBD; junction barrier Schottky diode, JBS; heterojunction diode, HJD) (a) output current-breakdown voltage and (b) specific on-resistance-breakdown voltage comprehensive performance comparison, the optimal device of the present work is at the forefront of the international level, still maintains good voltage resistance and current output ability under high temperature 450k test conditions.

[0044] The technical features of the above-mentioned embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, it should be considered that they are within the scope of the present disclosure.

[0045] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A gallium oxide surface treatment method for reducing the surface defect density of gallium oxide, characterized by, It comprises the following steps: The gallium oxide surface of the gallium oxide sample with epitaxial layer is bombarded by argon ions, or nitrogen ions, or helium ions; The gallium oxide surface after argon ion bombardment is treated by low-temperature oxygen annealing: oxygen flow rate is 0-100 sccm, annealing temperature is 300-800℃, and annealing time is 0-24h.

2. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized by, The argon ions, nitrogen ions, and helium ions are generated by 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 by, The inductively coupled plasma system includes ICP-RIE, or PECVD and sputtering system configured with ICP source.

4. The gallium oxide surface treatment method for reducing the surface defect density of gallium oxide according to claim 1, characterized by, Before the gallium oxide surface is bombarded by argon ions, the gallium oxide surface is cleaned by organic solution and piranha solution.

5. The gallium oxide surface treatment method for reducing a surface defect density of gallium oxide according to claim 1, characterized by, When the gallium oxide surface is bombarded by argon ions, the gallium oxide sample is placed in the inductively coupled plasma system, the ICP power of the system is set to 900W, the RIE power is set to 300W, the argon flow rate is set to 50 sccm, and the argon ion bombardment time is set to 30 minutes.

6. The gallium oxide surface treatment method for reducing a surface defect density of gallium oxide according to claim 1, characterized by, The low-temperature oxygen annealing is performed by a rapid thermal processing system, pure oxygen is introduced during the heating and cooling processes of the rapid thermal processing system, the temperature is raised from room temperature to a maximum temperature of 400℃ at a rate of 20℃ / s, and the maximum temperature of 400℃ is maintained for 30 minutes.

7. A gallium oxide sample, characterized by, It adopts the gallium oxide surface treatment method for reducing the defect density of the gallium oxide surface as claimed in any one of claims 1 to 6 to treat the gallium oxide surface of the gallium oxide sample.

8. A process for processing a semiconductor device, characterized by, It comprises: It adopts the gallium oxide surface treatment method for reducing the defect density of the gallium oxide surface as claimed in any one of claims 1 to 6 to treat the gallium oxide surface of the gallium oxide sample; The treated gallium oxide sample is subjected to a semiconductor device preparation process.

9. The process for manufacturing a semiconductor device according to Claim 8, wherein 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-shaped metal-oxide semiconductor field effect transistor.

10. A semiconductor device, characterized by comprising: It adopts the semiconductor device processing technology as claimed in claim 8 or 9 to prepare the semiconductor device.

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