5.5 GHz film bulk acoustic wave filters using thin film transfer process for WLAN applications  

作　　者：Tingting Yang Chao Gao Yaxin Wang Binghui Lin Yupeng Zheng Yan Liu Cheng Lei Chengliang Sun Yao Cai 

机构地区：[1]The Institute of Technological Sciences,Hubei Key Laboratory of Electronic Manufacturing and Packaging Integration,Wuhan University,430072 Wuhan,China [2]Hubei Yangtze Memory Laboratories,430205 Wuhan,China [3]School of Microelectronics,Wuhan University,430072 Wuhan,China

出　　处：《Microsystems & Nanoengineering》2024年第6期225-233,共9页微系统与纳米工程(英文)

基　　金：supported by the Young Scientists Fund of the National Natural Science Foundation of China under Grant 62204177;the National Key R&D Program of China under Grant 2022YFB3207101;the Fundamental Research Funds for the Central Universities under Grant 2042023kf0218;the Open Fund of Hubei Key Laboratory of Electronic Manufacturing and Packaging Integration(Wuhan University)under Grant EMPI2023025.

摘　　要：Wireless local area network(WLAN)has gained widespread application as a convenient network access method,demanding higher network efficiency,stability,and responsiveness.High-performance filters are crucial components to meet these needs.Film bulk acoustic resonators(FBARs)are ideal for constructing these filters due to their high-quality factor(Q)and low loss.In conventional air-gap type FBAR,aluminum nitride(AlN)is deposited on the sacrificial layer with poor crystallinity.Additionally,FBARs with single-crystal AlN have high internal stress and complicated fabrication process.These limit the development of FBARs to higher frequencies above 5 GHz.This paper presents the design and fabrication of FBARs and filters for WLAN applications,combining the high electromechanical coupling coefficient(K_(t)^(2))of Al_(0.8)Sc_(0.2)N film with the advantages of the thin film transfer process.An AlN seed layer and 280 nm-thick Al_(0.8)Sc_(0.2)N are deposited on a Si substrate via physical vapor deposition(PVD),achieving a full width at half maximum(FWHM)of 2.1°.The ultra-thin film is then transferred to another Si substrate by wafer bonding,flipping,and Si removal.Integrating conventional manufacturing processes,an FBAR with a resonant frequency reaching 5.5 GHz is fabricated,demonstrating a large effective electromechanical coupling coefficient(k_(eff)^(2))of 13.8%and an excellent figure of merit(FOM)of 85.A lattice-type filter based on these FBARs is then developed for the Wi-Fi UNII-2 band,featuring a center frequency of 5.5 GHz and a−3 dB bandwidth of 306 MHz,supporting high data rates and large throughputs in WLAN applications.

关 键 词：FILTERS FILM TRANSFER 

分 类 号：TN624[电子电信—电路与系统] TN304