硅基钽酸锂异质晶圆键合工艺研究

摘要/Abstract

摘要： 5G移动通信的发展对声表面波滤波器提出了高频、小型化、集成化的要求。相较于传统压电体单晶材料,采用硅基压电单晶薄膜材料制备的声表面波滤波器具有高频、低插入损耗、高温稳定性等优势,是高性能声表面波器件发展的核心基础材料。Smart-Cut^TM是制备硅基压电单晶薄膜材料的主要方法,键合工艺是其中的核心工序,键合质量决定了硅基压电单晶薄膜晶圆材料的质量,并影响器件性能。本文通过低温直接键合工艺,对等离子活化、兆声清洗、预键合、键合加固四道工序展开优化,最终实现了键合强度高达1.84 J/m²、键合面积超过99.9%的高质量硅基钽酸锂异质晶圆键合。

关键词: 硅基钽酸锂, 低温直接键合, 等离子活化, 兆声清洗, 预键合, 键合加固, 声表面波滤波器

Abstract: The development of 5G mobile communication imposes requirements of high frequency, miniaturization, and integration on surface acoustic wave devices. Compared with traditional piezoelectric bulk single crystal material, surface acoustic wave filters fabricated with silicon-based piezoelectric single crystal film materials exhibit advantages such as high frequency, low insertion loss, high temperature stability and so on, making silicon-based piezoelectric single crystal film material prime foundation material. Smart-Cut^TM is the universal method for preparing silicon-based piezoelectric single crystal film materials, and bonding process is one of the most essential procedures. Bonding quality determines the quality of piezoelectric single crystal film and ultimately affects the performance of the devices. In this work, high-quality heterogeneous silicon-based LiTaO₃ wafers with the bonding strength up to 1.84 J/m²and bonding area over 99.9% were achieved through optimizing low-temperature direct bonding process, which includes plasma activation, megasonic cleaning, pre-bonding, and thermal treatment.

Key words: silicon-based lithium tantalate, low-temperature direct bonding, plasma activation, megasonic cleaning, pre-bonding, thermal treatment, surface acoustic wave filter

中图分类号:

陈哲明, 丁雨憧, 邹少红, 龙勇, 石自彬, 马晋毅. 硅基钽酸锂异质晶圆键合工艺研究[J]. 人工晶体学报, 2024, 53(4): 634-640.

CHEN Zheming, DING Yuchong, ZOU Shaohong, LONG Yong, SHI Zibin, MA Jinyi. Study on Bonding Technology of Silicon-Based Lithium Tantalate Heterogeneous Wafers[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2024, 53(4): 634-640.

参考文献

[1] LU X M, MOUTHAAN K, SOON Y T. Wideband bandpass filters with SAW-filter-like selectivity using chip SAW resonators[J]. IEEE Transactions on Microwave Theory and Techniques, 2014, 62(1): 28-36.
[2] RUPPEL C C W. Acoustic wave filter technology-a review[J]. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2017, 64(9): 1390-1400.
[3] SU R X, SHEN J Y, LU Z T, et al. Wideband and low-loss surface acoustic wave filter based on 15° YX-LiNbO₃/SiO₂/Si structure[J]. IEEE Electron Device Letters, 2021, 42(3): 438-441.
[4] 刘宏, 桑元华, 孙德辉, 等. 信息时代的铌酸锂晶体: 进展与展望[J]. 人工晶体学报, 2021, 50(4): 708-715.
LIU H, SANG Y H, SUN D H, et al. Lithium niobate crystals in the information age: progress and prospect[J]. Journal of Synthetic Crystals, 2021, 50(4): 708-715 (in Chinese).
[5] BUTAUD E, TAVEL B, BALLANDRAS S, et al. Smart Cut^TM piezo on insulator (POI) substrates for high performances SAW components[C]//2020 IEEE International Ultrasonics Symposium (IUS). Las Vegas, NV, USA. IEEE, 2020: 1-4.
[6] HAISMA J, SPIERINGS G A C M, BIERMANN U K P, et al. Silicon-on-insulator wafer bonding-wafer thinning technological evaluations[J]. Japanese Journal of Applied Physics, 1989, 28(8): 1426.
[7] BRUEL M. Silicon on insulator material technology[J]. Electronics Letters, 1995, 31(14): 1201.
[8] BOES A, CORCORAN B, CHANG L, et al. Status and potential of lithium niobate on insulator (LNOI) for photonic integrated circuits[J]. Laser & Photonics Reviews, 2018, 12(4): 1700256.
[9] YAN Y Q, HUANG K, ZHOU H Y, et al. Wafer-scale fabrication of 42° rotated Y-cut LiTaO₃-on-insulator (LTOI) substrate for a SAW resonator[J]. ACS Applied Electronic Materials, 2019, 1(8): 1660-1666.
[10] 丁雨憧, 何杰, 陈哲明, 等. 硅基钽酸锂压电单晶复合薄膜材料及应用[J]. 压电与声光, 2023, 45(1): 66-71.
DING Y C, HE J, CHEN Z M, et al. Single-crystal LiTaO₃ composite film material on Si substrate and its applications[J]. Piezoelectrics & Acoustooptics, 2023, 45(1): 66-71 (in Chinese).
[11] JIA Y C, WANG L, CHEN F. Ion-cut lithium niobate on insulator technology: recent advances and perspectives[J]. Applied Physics Reviews, 2021, 8(1): 011307.
[12] KE S Y, LI D K, CHEN S Y. A review: wafer bonding of Si-based semiconductors[J]. Journal of Physics D Applied Physics, 2020, 53(32): 323001.
[13] 杨金凤, 商继芳, 李清连, 等. 非对称扩散工艺制备近化学计量比钽酸锂晶体的研究[J]. 人工晶体学报, 2022, 51(7): 1141-1146.
YANG J F, SHANG J F, LI Q L, et al. Preparation of near stoichiometric lithium tantalate crystal by asymmetric diffusion technique[J]. Journal of Synthetic Crystals, 2022, 51(7): 1141-1146 (in Chinese).
[14] THIRUMDAS R, KOTHAKOTA A, ANNAPURE U, et al. Plasma activated water (PAW): chemistry, physico-chemical properties, applications in food and agriculture[J]. Trends in Food Science & Technology, 2018, 77: 21-31.
[15] SAM M, JOJITH R, RADHIKA N. Progression in manufacturing of functionally graded materials and impact of thermal treatment—a critical review[J]. Journal of Manufacturing Processes, 2021, 68: 1339-1377.
[16] KIM M S, PURUSHOTHAMAN M, KIM H T, et al. Removal of EUV exposed hydrocarbon from Ru capping layer of EUV mask using the mixture of alkaline solutions and organic solvents[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018, 555: 72-79.
[17] 刘等等, 帅垚, 黄诗田, 等. 基于混合气体活化的硅基钽酸锂晶圆键合研究[J]. 电子元件与材料, 2023, 42(6): 693-698.
LIU D D, SHUAI Y, HUANG S T, et al. Si-based lithium tantalate wafer bonding based on mixed gas activation[J]. Electronic Components and Materials, 2023, 42(6): 693-698 (in Chinese).
[18] 许继开. LiNbO₃与硅基材料表面活化低温直接键合及应用研究[D]. 哈尔滨: 哈尔滨工业大学, 2021.
XU J K. Low-temperature direct bonding between LiNbO₃ and silicon-based materials and its application[D].Harbin: Harbin Institute of Technology, 2021 (in Chinese).
[19] ZHAI K, HE Q, LI L, et al. Study on chemical mechanical polishing of silicon wafer with megasonic vibration assisted[J]. Ultrasonics, 2017, 80: 9-14.
[20] LASKY J B. Wafer bonding for silicon-on-insulator technologies[J]. Applied Physics Letters, 1986, 48(1): 78-80.
[21] LOWEN W K, BROGE E C. Effects of dehydration and chemisorbed materials on the surface properties of amorphous silica[J]. The Journal of Physical Chemistry, 1961, 65(1): 16-19.
[22] HOCKEY J A, PETHICA B A. Surface hydration of silicas[J]. Transactions of the Faraday Society, 1961, 57: 2247-2262.
[23] PLACH T, HINGERL K, TOLLABIMAZRAEHNO S, et al. Mechanisms for room temperature direct wafer bonding[J]. Journal of Applied Physics, 2013, 113(9): 94905-94905-7.
[24] EICHLER M, MICHEL B, THOMAS M, et al. Atmospheric-pressure plasma pretreatment for direct bonding of silicon wafers at low temperatures[J]. Surface and Coatings Technology, 2008, 203(5/6/7): 826-829.
[25] SCHNELL M, HORST T, QUICKER P. Thermal treatment of sewage sludge in Germany: a review[J]. Journal of Environmental Management, 2020, 263: 110367.
[26] TAKAGI H. Direct bonding[J]. 3D and Circuit Integration of MEMS, 2021, 12: 279-288.
[27] LIM C M, ZHAO Z Q, SUMITA K, et al. Operation of (111) Ge-on-insulator n-channel MOSFET fabricated by smart-cut technology[J]. IEEE Electron Device Letters, 2020, 41(7): 985-988.
[28] TONG Q Y, CHA G, GAFITEANU R, et al. Low temperature wafer direct bonding[J]. Journal of Microelectromechanical Systems, 1994, 3(1): 29-35.
[29] MASZARA W P, GOETZ G, CAVIGLIA A, et al. Bonding of silicon wafers for silicon-on-insulator[J]. Journal of Applied Physics, 1988, 64(10): 4943-4950.
[30] 刘泽翰, 康汝燕, 程鹏鹏, 等. 晶圆低温直接键合技术研究进展[J]. 半导体光电, 2021, 42(5): 603-609.
LIU Z H, KANG R Y, CHENG P P, et al. Research progress of wafer low temperature direct bonding technology[J]. Semiconductor Optoelectronics, 2021, 42(5): 603-609 (in Chinese).
[31] YEO C Y, XU D W, YOON S F, et al. Low temperature direct wafer bonding of GaAs to Si via plasma activation[J]. Applied Physics Letters, 2013, 102(5): 054107.
[32] YANG R, WANG Z H, LEE J, et al. 6H-SiC microdisk torsional resonators in a “smart-cut” technology[J]. Applied Physics Letters, 2014, 104(9): 091906.
[33] PETER R A, JAMES J Q L, MAAIKE M V T. Handbook of wafer bonding[M]. Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2000: 101-105.
[34] MEYER R, KONONCHUCK O, MORICEAU H, et al. Study of high-temperature Smart Cut^TM: application to silicon-on-sapphire films and to thin foils of single crystal silicon[J]. Solid-State Electronics, 2016, 115: 225-231.