硅酸盐学报

氧等离子体活化β-Ga₂O₃/SiO₂低温键合工艺

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马旭 ¹^,² , 穆文祥 ¹^,² , 侯童 ¹ , 董岳 ¹ , 余博文 ¹ , 李阳 ¹ , 贾志泰 ¹^,³

硅酸盐学报 | 研究论文 2024,52(10): 3273-3282

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硅酸盐学报 |研究论文 2024 , 52 (10) : 3273 -3282

氧等离子体活化β-Ga₂O₃/SiO₂低温键合工艺

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马旭¹^,², 穆文祥¹^,², 侯童¹, 董岳¹, 余博文¹, 李阳¹, 贾志泰¹^,³

作者信息

^1．山东大学新一代半导体材料研究院，晶体材料国家重点实验室，济南 250100

^2．山东大学深圳研究院，广东深圳 518057

^3．山东省工业技术研究院，济南 250100

通讯作者:

贾志泰（1981—），男，博士，教授；

穆文祥（1989—），男，博士，副教授。

作者简介:

马旭（1998—），男，硕士研究生。

Low Temperature Bonding of β-Ga₂O₃/SiO₂ by Oxygen Plasma Activation

Xu MA¹^,², Wenxiang MU¹^,², Tong HOU¹, Yue DONG¹, Bowen YU¹, Yang LI¹, Zhitai JIA¹^,³

Affiliations

^1.Institute of Novel Semiconductors, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China

^2.Shenzhen Research Institute of Shandong University, Shenzhen 518057, Guangdong, China

^3.Shandong Research Institute of Industrial Technology, Jinan 250100, China

Corresponding Author:

JIA Zhitai (1981-), Male, Ph.D., Professor; E-mail: z.jia@sdu.edu.cn;

MU Wenxiang (1989-), Male, Ph.D., Associate Professor. mwx@sdu.edu.cn

MA Xu (1998-), male, Master candidate. E-mail: 2664773087@qq.com

出版时间: 2024-10-20 doi: 10.14062/j.issn.0454-5648.20240259

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摘要

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采用O₂等离子体活化键合技术，实现了β-Ga₂O₃与SiO₂的低温直接键合。通过对O₂等离子体处理时间进行调控，系统研究了接触角、羟基密度随处理时间的变化。随着O₂等离子体活化时间的增加，SiO₂和β-Ga₂O₃晶片表面亲水性大幅度增强，晶片表面的羟基密度明显提升。同时探究了退火温度对衬底表面质量及键合强度的影响，发现键合强度随着退火温度的增加而提升，但较高退火温度容易导致β-Ga₂O₃衬底的开裂。通过扫描电子显微镜和透射电子显微镜对键合界面进行分析，键合界面的O、Ga、Si元素在退火过程中发生充分扩散。测试说明，采用O₂等离子体活化方法成功地实现了β-Ga₂O₃/SiO₂晶片的异质集成。由于β-Ga₂O₃和SiO₂衬底可以在不需要真空处理的情况下实现原子级的结合，技术路线成本低，因此本工作提出的直接键合技术将有助于推动β-Ga₂O₃材料在器件方面的发展及应用。

关键词

β-氧化镓 / 二氧化硅 / 氧气等离子体活化 / 低温直接键合 / 异质集成

Abstract

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Introduction

β-Ga₂O₃ as a ultra-wide bandgap semiconductor material with a great development potential has a bandgap width of 4.8 eV, and a theoretical breakdown electric field of 8 MV/cm. Its Baliga advantage value of β-Ga₂O₃ is also several times greater than that of silicon carbide (SiC) or gallium nitride (GaN). However, the low thermal conductivity of β-Ga₂O₃ seriously affected the device's heat dissipation and the application in the high-power field. Wafer bonding is an indispensable key technology in semiconductor devices, which enables the formation of new structures, efficient fabrication, device integration, and cost reduction. The silicon substrate with the advantages of low cost and high thermal conductivity is an important substrate material for heterogeneous integrations. SiO₂ layer is easily formed on the surface of silicon, and the surface structure of SiO₂ consists of a Si-O-Si three-dimensional network structure together with an unsaturated Si-O structure, and the existence of this structure is conducive to reducing the probability of bubble generation, thus improving the quality of the bonding bonding interface, so it is easier to realize the bonding of silicon and β-Ga₂O₃ by using SiO₂ as an intermediate layer. This paper was to analyze the effect of O₂ plasma activation on the wafer surface, including changes in contact angle, roughness, and surface chemical composition. In addition, the effect of annealing temperature on the strength and thermal stability of the bond structure and the structure and composition of the β-Ga₂O₃/SiO₂ bond interface was also discussed.

Methods

SiO₂/Si substrate with the thickness of 550 μm and β-Ga₂O₃ single crystals sunstrate with the thickness of 650 μm were prepared. The two wafers were cleaned with alcohol and acetone via ultrasonic cleaning , and isopropanol for 10 min, then rinsed with deionized water and blown dry with N₂. Also, β-Ga₂O₃ and SiO₂/Si substrates were processed by oxygen plasma in a reactive ion etching (RIE) equipment (PlasmaPro 100 Cobra, Oxford Instrument Co., UK) at 50 mtorr and 300 W. The two activated wafers to be bonded were initially aligned and bonded, and pressure was applied to the wafer surface with tweezers to fully expel the gas from the bonding interface and make the bonding closer. Finally, the bonded wafers were placed on a pressurized platform for pressurized resting to complete the pre-bonding process. The pre-bonded wafers were placed in the annealing furnace for low-temperature annealing to enhance the bonding strength. A testing machine was used to determine the bond strength of the bonded pairs at different annealing temperatures. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to determine the bonded interface images and elemental distribution.

Results and discussion

The contact angle and hydroxyl density with treatment time were investigated via adjusting the treatment time of O₂ plasma. The hydrophilicity of SiO₂ and β-Ga₂O₃ wafers greatly enhances, and the hydroxyl density on the wafer surface improves as the O₂ plasma activation time increases. O-H in β-Ga₂O₃ is produced by the breakage of oxygen atoms (O_w) in water that combines with surface Ga atoms (Ga_s) to form Ga_s-O_wH_w, and H combines with surface oxygen atoms (O_s) to form O_s-H_w. The effect of annealing temperature on the surface quality and bonding strength was also investigated. The results indicate that the bonding strength increases with the increase of annealing temperature. When the annealing temperature increases to 500 ℃, the bond strength increases to 7.31 MPa. However, this process leads to the cracking of the β-Ga₂O₃ substrate. Some cracks in β-Ga₂O₃ occur due to the thermal stress resulting from the different thermal expansion coefficients between SiO₂ and β-Ga₂O₃. β-Ga₂O₃ and SiO₂ surfaces are atomically bonded with no interfacial voids or cracks. The bonding interface's elements O, Ga, and Si are fully diffused during annealing.

Conclusions

In this study, a high-strength bonding of β-Ga₂O₃ and SiO₂ substrates was achieved at low temperatures via O₂ plasma activation. The FTIR analysis showed an increase in the hydroxyl density of the β-Ga₂O₃ and SiO₂/Si surfaces with the increase in plasma treatment time. The XPS and FTIR analysis demonstrated the changes in the hydrophilic functional groups on the surfaces before and after the plasma treatments. The bond strength gradually increased with the annealing temperature and reached 7.31 MPa, but unbonding and cracking also occurred at the edges of the bonded regions. The SEM and TEM images of the bonding interface demonstrated the existence of tight bonding between β-Ga₂O₃ and SiO₂ with full diffusion of elements Ga, O, and Si. In addititon, a model for direct bonding of oxygen plasma-activated β-Ga₂O₃/SiO₂/Si was also proposed.

Key words

β gallium / silicon dioxide / oxygen plasma activation / low-temperature direct bonding / heterogeneous integration

引用本文

马旭, 穆文祥, 侯童, 董岳, 余博文, 李阳, 贾志泰. 氧等离子体活化β-Ga₂O₃/SiO₂低温键合工艺. 硅酸盐学报, 2024 , 52 (10) : 3273 -3282 . DOI: 10.14062/j.issn.0454-5648.20240259

Xu MA, Wenxiang MU, Tong HOU, Yue DONG, Bowen YU, Yang LI, Zhitai JIA. Low Temperature Bonding of β-Ga₂O₃/SiO₂ by Oxygen Plasma Activation[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (10) : 3273 -3282 . DOI: 10.14062/j.issn.0454-5648.20240259

基金

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国家自然科学基金(52002219; 51932004)
广东省重点研发计划(2020B010174002)
深圳市基础研究计划(JCYJ20210324 132014038)

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2024年第52卷第10期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240259

接收时间：2024-04-07
首发时间：2026-10-22
出版时间：2024-10-20

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出版历史

收稿日期：2024-04-07
修回日期：2023-04-27

基金

国家自然科学基金(52002219; 51932004)

广东省重点研发计划(2020B010174002)

深圳市基础研究计划(JCYJ20210324 132014038)

作者信息

^1．山东大学新一代半导体材料研究院，晶体材料国家重点实验室，济南 250100

^2．山东大学深圳研究院，广东深圳 518057

^3．山东省工业技术研究院，济南 250100

通讯作者:

贾志泰（1981—），男，博士，教授；

穆文祥（1989—），男，博士，副教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240259

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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