CN-120119334-B - Method for bonding diamond and gallium nitride

Abstract

The invention discloses a method for bonding diamond and gallium nitride, which comprises the steps of preparing monocrystalline diamond and a GaN epitaxial wafer, etching the GaN epitaxial wafer to form a layered ladder-shaped structure, bombarding the surface of the GaN epitaxial wafer by Ar ion beams, depositing an intermediate layer on the surface, thinning the intermediate layer until the intermediate GaN part is exposed after the deposition, polishing after the thinning is finished, respectively soaking the GaN and the monocrystalline diamond in acidic and alkaline solutions, mutually contacting and applying pressure to anneal for bonding after the thinning is finished, and removing a substrate of the GaN epitaxial wafer after the completion to finally obtain GaN/diamond. According to the invention, through the layered ladder-type structural design, not only can the bonding of diamond and GaN be realized, but also the interface thermal resistance can be effectively reduced, the contact area can be obviously increased, the GaN device can dissipate heat more uniformly and more fully, and the problem of difference of thermal expansion coefficients can be solved.

Inventors

• SUN QINGLEI
• LI SHILIN
• LIU FUCHU
• JIANG HONGYONG
• LI JIANING
• CHEN BOYUAN

Assignees

• 广州南沙地大滨海研究院
• 中国地质大学（武汉）
• 中国地质大学深圳研究院

Dates

Publication Date

20260505

Application Date

20250318

Claims (6)

1. 1. A method of bonding diamond to gallium nitride, the method comprising the steps of: s1, preparing single-crystal diamond (4) and GaN (2) grown on a sapphire or Si substrate (1), wherein Ra of the single-crystal diamond (4) is less than 10nm, and Ra of the GaN (2) is less than 5nm; S2, etching the GaN epitaxial wafer by using a mask with a layered step structure to form the layered step structure, and after etching is finished, carrying out ultrasonic cleaning and nitrogen drying on the GaN (2) and the monocrystal diamond (4); In S2, the GaN epitaxial wafer is etched into a three-layer stepped structure, and the method of etching into the three-layer stepped structure includes, but is not limited to, chemical etching, plasma etching, and electron beam etching; in S2, the method for etching the GaN epitaxial wafer into the three-layer stepped structure includes: 1) The etching depth of the first layer is 50-70nm, and a wide convex structure of the bottommost layer is formed; 2) The etching depth of the second layer is 25-40nm, and a convex structure of the middle layer is formed; 3) The etching depth of the third layer is 50-120nm, and a convex structure of the uppermost layer is formed; S3, carrying out bombardment treatment on the surface of the GaN (2) by using Ar ion beams, removing the oxide layer, activating the surface of the GaN (2), then growing a buffer layer on the surface of the GaN (2), and simultaneously filling the buffer layer on two sides of the step and covering the middle GaN (2); in the step S3, a buffer layer grown on the surface of the GaN (2) is an SiC or AlN intermediate layer (3); In the step S3, the method for growing the buffer layer on the surface of the GaN (2) specifically comprises the following steps: 1) The buffer layer is filled at two sides of the bottommost convex structure to form a first layer structure; 2) The buffer layer is filled at two sides of the convex structure of the middle layer to form a second layer structure; 3) The buffer layer fills two sides of the uppermost convex structure to form a third layer structure and completely covers the GaN (2); s4, thinning the grown buffer layer until the middle area of the GaN (2) is exposed, and polishing; S5, respectively soaking the thinned and polished GaN epitaxial wafer and the monocrystalline diamond (4) in different solutions; S6, washing the soaked GaN epitaxial wafer and monocrystalline diamond (4) with deionized water and drying with nitrogen to obtain a GaN epitaxial wafer sample and a monocrystalline diamond (4) sample, contacting the GaN epitaxial wafer sample and the monocrystalline diamond (4) sample with each other, applying pressure to bond the GaN epitaxial wafer and the monocrystalline diamond (4) sample while annealing at a high temperature, and removing the substrate on the GaN epitaxial wafer after the completion of the annealing to obtain the target GaN/diamond.
2. 2. The method of claim 1, wherein in S2, the ultrasonic cleaning method sequentially uses acetone, acetone and deionized water for ultrasonic cleaning for 5-10min.
3. 3. The method of claim 1, wherein the step S3 of growing a buffer layer on the GaN (2) surface includes, but is not limited to, a plasma-enhanced chemical vapor deposition method and a magnetron sputtering method.
4. 4. The method according to claim 1, wherein in S5, the GaN epitaxial wafer is soaked by an acid solution, and the sapphire or Si substrate (1) is soaked by an alkali solution, wherein the acid solution comprises, but is not limited to, dilute hydrochloric acid and dilute sulfuric acid, and the alkali solution comprises, but is not limited to, naOH, NH 4 OH and H 2 O 2 .
5. 5. The method of claim 1, wherein the high temperature annealing is performed at 200-350 ℃ for 2-3 hours under a pressure of 1-2MPa in S6.
6. 6. The method of claim 1, wherein the step S6 comprises removing the substrate on the GaN epitaxial wafer by mechanical separation and laser separation.

Description

Method for bonding diamond and gallium nitride Technical Field The invention relates to an integration method of gallium nitride and diamond based on low interface thermal resistance, and belongs to the technical field of semiconductors. Background At present, with the rapid development of modern electronic devices in the directions of high frequency, high power and high integration, more stringent requirements are placed on the thermal management capability of semiconductor materials, especially in the fields of high-power electronic devices and high-frequency microwave devices. Gallium nitride (GaN) exhibits excellent application potential due to its unique physical properties such as a wide forbidden band, a high intrinsic breakdown electric field, and a high electron saturation rate. The theoretical power density of the GaN-based power device is very high, however, in practical application, the power density of the GaN-based power device can only reach one fourth of the theoretical power density due to the severe self-heating effect of the device in the high power mode, which is mainly caused by that heat generated by the GaN-based power device during high power operation can be rapidly accumulated and difficult to effectively dissipate. In general, gaN power devices are generally fabricated on silicon and silicon carbide substrates, but the thermal conductivity of these original substrates is relatively low, and the heat dissipation requirement cannot be met, resulting in serious degradation of the device performance, which greatly limits the application range of GaN power devices. Therefore, how to increase the thermal management level of GaN devices becomes a key to further enhance their performance. Diamond is considered as an ideal high power electronics substrate material as it has an ultra-high thermal conductivity, as well as a very low coefficient of thermal expansion, a high electrical resistivity, and excellent chemical inertness. The diamond and the GaN are integrated, so that the heat radiation capability of a near junction region of the GaN device can be effectively improved, and the peak temperature is reduced, thereby remarkably improving the reliability and performance of the device. In the prior art, the integration method of diamond and GaN is mainly divided into three types, namely growing GaN on the diamond, growing diamond on the GaN and bonding the diamond and the GaN. The former two methods limit the application thereof in practical production due to lattice mismatch and thermal expansion coefficient difference between materials, and problems of wafer warpage, breakage and the like caused by high-temperature processes. Therefore, the bonding technique of diamond and GaN is a good solution. The bonding technology of diamond and GaN in the prior art comprises 1) bonding the embedded structure of the bulge and the groove by adopting the bonding method disclosed by the publication No. CN111599693A, well controlling the thickness of soldering paste by extruding and jogging the copper nano paste in the groove to form more uniform soldering paste, being beneficial to reducing bonding defects and helping to improve the strength of a product, and 2) forming the gallium nitride semiconductor structure disclosed by the publication No. CN113299736A and the preparation method thereof, wherein dislocation density can be further reduced in the growth process and dislocation can be concentrated to a certain specific area to form a defect folding area, gallium nitride materials formed by other growth areas have few dislocation defects, and then forming grooves and insulating barrier layers on the defect folding area, wherein the insulating barrier layers can block electrode metal and impurity metal elements from diffusing into the dislocation, so that a leakage channel cannot be formed, and the gallium nitride layer below an ohmic contact area or a Schottky contact area has no dislocation, thereby improving the reliability and stability of the device. However, in the bonding technology of diamond and GaN, the intermediate layers such as Si, siO 2 and SiC can be used for avoiding the lattice mismatch and the difference of thermal expansion coefficients generated by high-temperature growth, but the interface thermal resistance can be increased, the metal diffusion technology such as Au, ag, mo, cu can be used for increasing the bonding strength, but the thermal conductivity is affected, and the problem of the difference of the thermal expansion coefficients is brought about, the direct bonding of diamond and GaN can not reduce the thermal conductivity, but the problem of insufficient bonding strength and unmatched thermal expansion coefficients exists, the traditional bonding structure usually adopts a planar contact design, the contact area is limited, the interface thermal resistance is higher, heat is easily accumulated at the interface, the heat dissipation performance of a device is influenced