Method for reducing electric leakage of GaN HEMT device after F injection isolation and application

Abstract

The invention discloses a method for reducing electric leakage of a GaN HEMT (High Electron Mobility Transistor) device after F injection isolation and application. The method comprises the following steps: providing a device substrate which comprises a substrate, a buffer layer, a channel layer and a barrier layer; f ion implantation processing is carried out on the device substrate in a selected area on the surface of the barrier layer, an F implantation area is formed, and the selected area is located between the source electrode and the drain electrode; and carrying out plasma treatment on the surface of the F injection region by adopting oxygen-containing plasma, so that the material of the part, close to the surface, of the F injection region is converted into an O treatment region. According to the technical scheme provided by the invention, the fluorine ion implantation isolation technology is combined with the oxygen plasma processing method, so that the electric leakage phenomenon can be reduced, and the overall performance of the device is further improved. The method not only can provide guidance for in-depth research of AlGaN / GaN HEMT devices, but also is expected to promote rapid development of GaN-based device technology, and brings breakthrough change to the fields of power electronics, microwave radio frequency and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of power semiconductors, and in particular to a method and application for reducing leakage of a GaN HEMT device after F injection isolation. Background Art

[0002] The third-generation semiconductor material GaN has shown great development potential in the field of high frequency and high power due to its unique physical properties. GaN has attracted much attention in the fields of power electronics and microwave radio frequency due to its large bandgap, high breakdown field strength, good temperature resistance and high electron mobility. Especially in AlGaN / GaN high electron mobility transistors (HEMTs), due to the polarization effect, a high concentration of two-dimensional electron gas (2DEG) can be generated at the heterojunction interface without doping. This feature makes the electron mobility of the AlGaN / GaN heterojunction interface far exceed that of ordinary GaN materials. This high electron mobility not only improves the performance of the device, but also provides a solid foundation for high-frequency and high-power applications.

[0003] A device’s isolation technology has a significant impact on its noise performance, breakdown voltage, and switching characteristics, so in-depth research in this area is critical. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a method and application for reducing leakage of a GaN HEMT device after F injection isolation.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: In a first aspect, the present invention provides a method for reducing leakage of a GaN HEMT device after F injection isolation, and also a method for preparing a GaN HEMT device with high isolation performance, which comprises: Providing a device substrate, the device substrate comprising a substrate, a GaN buffer layer, a GaN channel layer, and an AlGaN barrier layer stacked in sequence along a specified direction; Performing F ion implantation on the device substrate in a selected area on the surface of the AlGaN barrier layer to form an F implantation area, wherein the selected area is between the source and the drain of the GaN HEMT device; On the surface of the F-implanted region, plasma treatment is performed using oxygen-containing plasma, so that a portion of the material adjacent to the surface of the F-implanted region is converted into an O-treated region.

[0006] In a second aspect, the present invention further provides a GaN HEMT device, comprising a GaN buffer layer, a GaN channel layer, and an AlGaN barrier layer stacked in sequence along a specified direction; a source and a drain are arranged on the AlGaN barrier layer, and in a partial area between the source and the drain, part of the material of the GaN buffer layer, the GaN channel layer, and the AlGaN barrier layer is converted into a processing area, and the processing area comprises an F-implanted area and an O-processed area stacked in sequence along the specified direction, and the O-processed area is adjacent to the surface of the AlGaN barrier layer.

[0007] In a third aspect, the present invention further provides applications of the above-mentioned GaN HEMT device in the field of power electronics or microwave radio frequency.

[0008] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention at least include: The technical solution provided by the present invention adopts fluorine ion implantation isolation technology combined with oxygen plasma treatment method, which can reduce leakage phenomenon and thus improve the overall performance of the device. It can not only provide guidance for the in-depth research of AlGaN / GaN HEMT devices, but also is expected to promote the rapid development of GaN-based device technology and bring breakthrough changes to the fields of power electronics and microwave radio frequency.

[0009] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the device structure after F ion implantation without silicon nitride passivation provided in a typical implementation case of the present invention; Figure 2 It is a schematic diagram of a device structure after F ion implantation without silicon nitride passivation and then O plasma treatment provided in a typical implementation case of the present invention; Figure 3 It is a schematic diagram of a device structure after F ion implantation after silicon nitride passivation provided in a typical implementation case of the present invention; Figure 4 It is a schematic diagram of a device structure after silicon nitride passivation is sequentially subjected to F ion implantation treatment and O plasma treatment, provided in a typical implementation case of the present invention; Figure 5 The current-voltage curves of the device with and without silicon nitride passivation followed by F ion implantation and then O plasma treatment are provided in two typical implementation cases of the present invention; Figure 6is a current-voltage curve diagram of a device treated with O plasma having different surface treatment areas provided in a typical embodiment of the present invention; Figure 7 is a current-voltage curve diagram of a device treated with O plasma at different powers provided in a typical embodiment of the present invention; Figure 8 It is a Srim simulation vacancy map of a device after F ion implantation provided by a typical implementation case of the present invention; Fig. 9 This is an XPS test spectrum of two devices before and after O plasma treatment provided by a typical implementation case of the present invention.

[0011] Explanation of the reference numerals: 1. substrate; 2. GaN buffer layer; 3. GaN channel layer; 4. AlGaN barrier layer; 5. F-implanted region; 6. O-treated region; 7. electrode; 8. silicon nitride passivation layer. DETAILED DESCRIPTION

[0012] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0013] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0014] See also Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a method for reducing leakage of a GaN HEMT device after F injection isolation, which comprises the following steps: Providing a device substrate, the device substrate comprising a substrate 1, a GaN buffer layer 2, a GaN channel layer 3, and an AlGaN barrier layer 4 which are sequentially stacked in a specified direction; Performing F ion implantation on the device substrate in a selected area on the surface of the AlGaN barrier layer 4 to form a F implantation area 5, wherein the selected area is between the source and the drain of the GaN HEMT device; On the surface of the F-implanted region 5 , plasma treatment is performed using oxygen-containing plasma, so that a portion of the material adjacent to the surface of the F-implanted region 5 is converted into an O-treated region 6 .

[0015] In some embodiments, the depth of the F-implanted region 5 extends from the surface of the AlGaN barrier layer 4 to the GaN buffer layer 2 .

[0016] In some embodiments, the depth of the O-treated region 6 is lower than the thickness of the GaN channel layer 3 .

[0017] The main technical means of the technical solution provided by the present invention lies in the combination of F ion implantation treatment and O plasma treatment to form a device structure with a composite treatment area; some prior arts use O plasma to treat the gate area of ​​the HEMT device, but the treatment concept is obviously different from that of the present invention. It is necessary to etch and remove the barrier layer of the treatment area, expose the channel layer, and then perform O plasma treatment. However, the present invention performs O plasma treatment on the surface of the material after F implantation isolation, and the formed O treatment area is at least in the barrier layer. The principle of improving leakage is also obviously different. The O treatment depth mentioned in the present invention should not exceed the barrier layer as much as possible, because according to the research results of the inventor of the present invention, the depth of the structural barrier layer is approximately equal to the area with the most ion implanted N vacancies obtained by SRIM simulation. Since the surface N displacement energy is relatively large, the material is sputtered under high-energy F implantation, and the near-surface N cannot be repaired by annealing. At this time, the oxygen plasma treatment will play a role, otherwise the O plasma treatment is too deep and will increase the leakage.

[0018] Regarding specific treatment conditions, in some embodiments, the F ion implantation treatment has an implantation energy of 40-120 keV and an implantation dose of 4×10 12 -1.2×10 14 cm -2 / ion.

[0019] In some embodiments, the plasma treatment has a power of 100-400 W and a duration of 1-4 min.

[0020] In some embodiments, the atmosphere used for the plasma treatment is pure oxygen, and the pressure is generally 0.5-2Pa.

[0021] In some embodiments, the method may further comprise the steps of: A source electrode and a drain electrode are deposited on the surface of the AlGaN barrier layer 4, that is, two electrodes 7 shown in the figure; An annealing process is performed in a protective atmosphere to form an ohmic contact between the source and the drain.

[0022] In a specific application case, the contact formed by the electrode 7 is an ohmic contact, and the metal used is several of Ti / Al / Ni / Au / Pt, and the deposition method is not limited to magnetron sputtering or electron beam evaporation.

[0023] Correspondingly, the embodiment of the present invention further provides a GaN HEMT device, see Figure 2As shown, it includes a GaN buffer layer 2, a GaN channel layer 3, and an AlGaN barrier layer 4 which are sequentially stacked along a specified direction; a source and a drain are arranged on the AlGaN barrier layer 4, and in a partial area between the source and the drain, part of the material of the GaN buffer layer 2, the GaN channel layer 3, and the AlGaN barrier layer 4 is converted into a processing area, and the processing area includes an F injection area 5 and an O processing area 6 which are sequentially stacked along the specified direction, and the O processing area 6 is adjacent to the surface of the AlGaN barrier layer 4.

[0024] Regarding specific size characteristics, in some embodiments, the AlGaN barrier layer 4 has a thickness of 15-25 nm and an Al component ratio of 0.2-0.3.

[0025] In some embodiments, the GaN channel layer 3 has a thickness of 50 nm to 200 nm.

[0026] In some embodiments, the GaN buffer layer 2 has a thickness of 2000-4000 nm.

[0027] In addition, the substrate 1 can be made of Si material, and the thickness is generally about 1 mm, but is not limited thereto.

[0028] Corresponding to the above preferred structural features, in some embodiments, the depth of the O-treated region 6 is about 50% of the thickness of the AlGaN barrier layer 4 , and usually fluctuates within the range of 20-80%.

[0029] In some embodiments, the GaN HEMT device further includes a gate formed within a projection area of ​​the process region along the specified direction.

[0030] In addition, an embodiment of the present invention also provides applications of the above-mentioned GaN HEMT device in the field of power electronics or microwave radio frequency.

[0031] In the typical representative implementation cases provided by the present invention, the leakage phenomenon under the isolation technology was carefully tested and analyzed, aiming to explore the specific causes of the leakage and provide guidance for the in-depth study of AlGaN / GaN HEMT devices.

[0032] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0033] Example 1 Step 1: First, a GaN buffer layer (4000nm thick), a GaN channel layer (200nm thick), and an AlGaN barrier layer (15nm thick) are grown from bottom to top on a silicon substrate by metal organic chemical vapor deposition.

[0034] Step 2: Use acetone, isopropanol and water to ultrasonicate for 5 minutes in sequence, then blow dry with N2, photolithograph the alignment marks, and etch the marks using Cl-based gas using ICP equipment; Step 2: Use acetone, isopropanol and water to ultrasonicate for 5 minutes, blow dry with N2, photolithography the device F ion implantation isolation area, and then perform high-energy F ion implantation isolation. The implantation energy is 40keV, 80keV, 120keV and the dose is 4×10 12 , 6×10 13 , 1.2×10 14 cm -2 / ion.

[0035] Step 3: Use oxygen plasma (the atmosphere for generating plasma is pure oxygen) to treat the surface F implantation area at a power of 300W, a time of 2min, and a temperature of 25°.

[0036] Step 4: Use acetone, isopropanol and water to ultrasonicate for 5 minutes in sequence, then blow dry with N2, photolithograph the ohmic contact pattern, and use electron beam evaporation or magnetron sputtering to deposit metal to form the drain and source on both sides.

[0037] Step 5: Use rapid annealing furnace for high temperature annealing at 850°C for 30s in N2 atmosphere to form ohmic contact.

[0038] Comparative Example 1 This comparative example is substantially the same as Example 1, the main difference being that the third step of oxygen plasma treatment is eliminated.

[0039] Figure 5 The voltage-current curves of the devices provided in the above embodiments and comparative examples are shown. It can be seen that in comparative example 1, after fluorine ion implantation, the leakage current of the device is still large. In embodiment 1, after adding oxygen plasma treatment, the leakage current at 200V can be reduced from 1.2e -5 A is reduced to 3.7e -10 A.

[0040] like Figure 8 As shown in FIG. 1 , the surface vacancies of the device provided in Comparative Example 1 were simulated using srim simulation, and it was found that after F injection within 40nm near the surface, N vacancies were significantly more than metal vacancies, while the internal N vacancies could be significantly restored by annealing, indicating that N vacancies played a major role in the surface and caused leakage after F injection. Then, XPS (X-ray photoelectron spectroscopy) tests were performed on the device samples of Example 1 and Comparative Example 1. Fig. 9As shown in the figure, after oxygen plasma treatment, the Ga3d peak increases from 19.6ev to 19.8ev, with an obvious positive bias and an increase in the Ga-O phase content, which should be the main influencing factor for achieving good leakage performance. After F injection, N vacancies will be generated on the surface of the AlGaN material. It is these N vacancies that cause leakage. O plasma treatment can compensate for the N vacancies to a certain extent and re-combine with the metal to form oxides to reduce leakage.

[0041] Example 2 This embodiment is substantially the same as the embodiment 1, except that after the first step, a 10 nm silicon nitride passivation layer 8 is grown by LPCVD (low pressure chemical vapor deposition) for protection. The device structure after the O plasma treatment is as follows: Figure 4 shown.

[0042] Comparative Example 2 This embodiment is substantially the same as the embodiment 2, except that the third step of oxygen plasma treatment is omitted, and the device structure after F ion implantation is as follows: Figure 3 As shown,.

[0043] As shown in FIG5, the voltage-current curves of four devices with or without silicon nitride passivation protection and with or without oxygen plasma treatment are provided. It can be found that in Comparative Example 1 and Example 1, no silicon nitride passivation layer is made, so the current difference at 200V with or without oxygen plasma treatment is quite obvious, and the improvement of leakage current by oxygen plasma treatment is very significant; in Example 2 and Comparative Example 2, the current at 200V is 2.3e -9 A, 8.4e after O plasma treatment -10 A, the change is not obvious, and the two curves are relatively close.

[0044] like Figure 8 As shown, the surface vacancy of the device provided in Comparative Example 2 was simulated using srim simulation, and it was found that the N vacancies after F injection within 40nm near the surface were almost the same as the metal vacancies. The presence of silicon nitride effectively reduced the surface damage under high-energy fluorine injection. It can be shown from the side that increasing the thickness of silicon nitride can well reduce the leakage generation, but prevents the significant improvement of the F injection area by O plasma treatment, which shows that the combination of F ion implantation and O plasma treatment provided by the present invention needs to be performed on the surface of the original AlGaN barrier layer without a surface passivation layer.

[0045] Example 3 This embodiment is substantially the same as the embodiment 1, the difference mainly lies in studying the influence of the size of different O-processed regions on the leakage current, as shown below: Using different oxygen plasma treatment ranges, the oxygen plasma treatment power is 300w, the time is 2min, and the treatment effect of the treatment area with a width of 150um and a length of 4, 8, and 12um is studied. The test results are as follows Figure 6 As shown, the leakage current at 200V is 2.1×10 -10 A, 9.2×10 -9 A, 1.6×10 -9 A. It can be found that the larger the scope of the oxygen-treated fluorine ion implantation damage area, the smaller the leakage current, indicating that the scope of O plasma treatment is positively correlated with the effect of improving leakage current.

[0046] Example 4 This embodiment is substantially the same as the embodiment 1. This embodiment studies the influence of the depth of the O-treated area formed by the O plasma treatment on the leakage current. We use the power side of the treatment to reflect the depth of the O-treated area. The influence on the leakage current of the device is specifically as follows: like Figure 7 As shown in the figure, the power of different O plasmas after F injection was compared. With the increase of O plasma power, that is, the increase of treatment depth, it was found that the leakage current gradually decreased from 100 to 300W. It reached the minimum at 300W under 200V, which was 4.6e -9 A, and at 400W, the current at 200V increases to 1.2e -8 A. We can hypothesize and infer the effect of oxygen plasma at different depths. After high-energy F injection, due to sputtering at a depth near the surface, and the displacement energy of nitrogen is greater than that of metal, there is a maximum value of N vacancies in the middle. When the oxygen treatment power reaches 300w, the leakage treatment effect tends to saturation. In this state, continuing to increase the power will affect the injection of O into the deep layer of the material, which will increase the leakage. It may be because the N vacancies inside the material will be repaired by annealing. After O injection, some defects may be formed to further increase the current. Therefore, when the power reaches 400w, the power should not be increased any further, otherwise it may cause the leakage current to increase in the opposite direction.

[0047] Based on the above test results, it is clear that the technical solution provided by the embodiment of the present invention adopts fluorine ion implantation isolation technology combined with oxygen plasma treatment method, which can reduce leakage phenomenon and thus improve the overall performance of the device. It can not only provide guidance for the in-depth research of AlGaN / GaN HEMT devices, but also is expected to promote the rapid development of GaN-based device technology and bring breakthrough changes to power electronics and microwave radio frequency fields.

[0048] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing leakage of a GaN HEMT device after F injection isolation, characterized in that: include: Providing a device substrate, the device substrate comprising a substrate, a GaN buffer layer, a GaN channel layer, and an AlGaN barrier layer stacked in sequence along a specified direction; Performing F ion implantation on the device substrate in a selected area on the surface of the AlGaN barrier layer to form an F implantation area, wherein the selected area is between the source and the drain of the GaN HEMT device; On the surface of the F-implanted region, plasma treatment is performed using oxygen-containing plasma, so that a portion of the material adjacent to the surface of the F-implanted region is converted into an O-treated region.

2. The method according to claim 1, characterized in that The depth of the F-implanted region extends from the surface of the AlGaN barrier layer to the GaN buffer layer; the depth of the O-treated region is lower than the thickness of the GaN channel layer and does not exceed the interface between the GaN channel layer and the AlGaN barrier layer.

3. The method according to claim 1, characterized in that The F ion implantation process has an implantation energy of 40-120 keV and an implantation dose of 4×10 12 -1.2×10 14 cm -2 / ion.

4. The method according to claim 1, characterized in that: The power of the plasma treatment is 200-400W, and the time is 1-4min; the atmosphere used for the plasma treatment is pure oxygen, and the pressure is 0.5-2Pa.

5. The method according to claim 1, characterized in that Also includes: Depositing a source electrode and a drain electrode on the surface of the AlGaN barrier layer; An annealing process is performed in a protective atmosphere to form an ohmic contact between the source and the drain.

6. A GaN HEMT device, characterized in that: It includes a GaN buffer layer, a GaN channel layer, and an AlGaN barrier layer which are sequentially stacked along a specified direction; a source and a drain are arranged on the AlGaN barrier layer, and in a partial area between the source and the drain, part of the material of the GaN buffer layer, the GaN channel layer, and the AlGaN barrier layer is converted into a processing area, and the processing area includes an F-injected area and an O-processed area which are sequentially stacked along the specified direction, and the O-processed area is adjacent to the surface of the AlGaN barrier layer.

7. The GaN HEMT device according to claim 6, characterized in that: The thickness of the AlGaN barrier layer is 15-25 nm, and the Al component ratio is 0.2-0.

3.

8. The GaN HEMT device according to claim 6, characterized in that: The thickness of the GaN channel layer is 50nm-200nm; And / or, the thickness of the GaN buffer layer is 2000-4000nm.

9. The GaN HEMT device according to claim 6, characterized in that: The depth of the O-treated region is 20-80% of the thickness of the AlGaN barrier layer.

10. Application of the GaN HEMT device according to any one of claims 6 to 9 in the field of power electronics or microwave radio frequency.

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