体声波滤波器的设计与微加工方法
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摘要
提出了一种易于使用的薄膜体声波(FBAR)滤波器的4步设计方法,以一种FDD-LTE Band7的Rx滤波器为例展示了该方法的应用流程。第一步,根据FBAR滤波器的中心频率和带宽指标,确定FBAR薄膜叠层中各层薄膜的厚度。第二步,得到滤波器的电路结构。第三步,得到每个FBAR单元的谐振区面积;为此,将串联FBAR单元的谐振区面积、并联FBAR单元与串联FBAR单元的谐振区面积比值作为两组优化参数;将给定滤波器的插入损耗和带外抑制指标作为优化目标,利用ADS软件中的梯度优化算法,得到其优化值。第四步,旨在使滤波器的带内纹波最小化。设计中采用一种新的FBAR电极厚度调整方法,故意使串联FBAR的串联谐振频率与并联FBAR的并联谐振频率频率值不等,但相差很小,实现了该目标。由于案例设计结果中,SiO2支撑层的厚度仅300nm,需要在背面通孔刻蚀的微加工工艺中工序保留良好,因此,提出了一种基于绝缘衬底上的Si(SOI)圆片中埋氧层(BOX)缓冲的两步通孔刻蚀工艺方案,该方法利用了BOX的刻蚀自停止特性。研究结果表明,Rx滤波器插入损耗为0.6dB,在Tx频段的带外抑制为40.4dB,带内纹波为0.4dB。由此验证了该设计方法的可行性。
An easy-to-use 4-step design method for FBAR filters was presented,and demonstrated by a design case of FBAR Rx filter for FDD-LTE Band 7.According to the center frequency and bandwidth of FBAR filter,the thicknesses of each film in the FBAR film stack layer were determined at the step 1.The step 2gets the filter′s circuit architecture.In the step 3,we obtain the active area of each FBAR unit.To get this,the active area of series FBAR units and the ratio of active area of parallel FBAR units and series FBAR units were used as two groups of optimization parameters reasonably.Taking the given insertion loss and out-of-band rejection of filter as the optimization objectives,we obtained the optimized values by the algorithm based on gradient in ADS software.The step 4aimed at minimizing the filter passband ripple.In the design case,this aim was fulfilled by a novel FBARs′electrode layer thickness adjusting method,and intentionally slightly mismatched the series resonant frequency of the series FBAR units with the parallel resonant frequency of the parallel FBAR units.As in the design case results,a SiO_2 support layer with only 300 nm needed to survive the backside viahole etching micro-fabrication process,a buried oxide layer(BOX)buffered 2-step via-hole etching scheme was proposed in this work,which taking advantage of the etching self-stop characteristic of BOX.The study results showed that the insertion loss of the Rx filter was 0.6dB,out-of-band rejection in Tx frequency band was 40.4dB and the passband ripple was 0.4dB.The feasibility of the design method was validated from this.
An easy-to-use 4-step design method for FBAR filters was presented,and demonstrated by a design case of FBAR Rx filter for FDD-LTE Band 7.According to the center frequency and bandwidth of FBAR filter,the thicknesses of each film in the FBAR film stack layer were determined at the step 1.The step 2gets the filter′s circuit architecture.In the step 3,we obtain the active area of each FBAR unit.To get this,the active area of series FBAR units and the ratio of active area of parallel FBAR units and series FBAR units were used as two groups of optimization parameters reasonably.Taking the given insertion loss and out-of-band rejection of filter as the optimization objectives,we obtained the optimized values by the algorithm based on gradient in ADS software.The step 4aimed at minimizing the filter passband ripple.In the design case,this aim was fulfilled by a novel FBARs′electrode layer thickness adjusting method,and intentionally slightly mismatched the series resonant frequency of the series FBAR units with the parallel resonant frequency of the parallel FBAR units.As in the design case results,a SiO_2 support layer with only 300 nm needed to survive the backside viahole etching micro-fabrication process,a buried oxide layer(BOX)buffered 2-step via-hole etching scheme was proposed in this work,which taking advantage of the etching self-stop characteristic of BOX.The study results showed that the insertion loss of the Rx filter was 0.6dB,out-of-band rejection in Tx frequency band was 40.4dB and the passband ripple was 0.4dB.The feasibility of the design method was validated from this.
引文
[1]BAUER T,EGGS C,WAGNER K,et al.A bright outlook for acoustic filtering:a new generation of very low-profile SAW,TC SAW,and BAW devices for module integration[J].IEEE Microwave Magazine,2015,16(7):73-81.
[2]ZHANG Y,CHEN D.Multilayer integrated film bulk acoustic resonators[M].Shanghai:SJTU Press,2012.
[3]SHIRAKAWA A A,PHAM J M,JARRY P,et al.Design of FBAR filters at high frequency bands[J].International Journal of RF&Microwave Computeraided Engineering,2007,17(1):115-122.
[4]SHIN J S,SONG I,KIM C S,et al.Balanced RF duplexer with low interference using hybrid BAW resonators for LTE application[J].ETRI Journal,2014,36(2):317-320.
[5]LAKIN K M,KLINE G R,MCCARRON K T.High-Q microwave acoustic resonators and filters[J].Microwave Theory and Technique,1993,41(12):2139-2146.
[6]GEVORGIAN S,TAGANTSEV A,VOROBIEV A K.Tuneable film bulk acoustic wave resonators[M].Berlin:Springer Press,2013.
[7]高杨,蔡洵,贺学锋,等.体声波滤波器的片上测试与性能表征[J].压电与声光,2015,37(5):729-733.GAO Yang,CAI Xun,HE Xuefeng,et al.On-wafer test and characterization of bulk acoustic wave filter[J].Piezoelectrics&Acoustooptics,2015,37(5):729-733.
[8]WANG K,CLARK D,CAMNITZ L H,et al.A UMTS-900duplexer[C]//Beijing:Ultrasonics Symposium,2008:899-902.
[9]汤亮,郝震宏,乔东海.支持层结构对薄膜体声波谐振器谐振特性的影响[C]//景洪市:中国西部地区声学学术交流会论文集,2009.
[10]REDDY P R,MOHAN B C.Design and analysis of film bulk acoustic resonator(FBAR)filter for RF applications[J].International Journal of Engineering Business Management,2012,4(29):1-4.
[11]LISE C,SYLVAIN G,MATTHIEU C,et al.A general procedure for the design of bulk acoustic wave filters[J].International Journal of RF&Microwave Computer-aided Engineering,2011,21(5):458-465.
[12]MULLER C,DUBOIS M A.Effect of size and shape on the performances of BAW resonators:a model and its applications[J].Proceedings of the IEEE Ultrasonics Symposium,2008:1552-1556.
[13]JIN H,DONG S,WANG D.Design of balanced RF filter for wireless applications using FBAR technology[C]//Beijing:Electron Devices and Solid-State Circuits,2005:57-60.
[14]LEE J,KIM H.Thin-film bulk acoustic resonator RF bandpass filter design technique using genetic algorithm[J].Electronics Letters,2003,39(5):444-445.
[15]FANG C M,PAO S Y,LEE C Y,et al.Development of 2.4GHz film bulk acoustic wave filter for wireless communication[J].Journal of Micro/Nanolithography Mems&Moems,2009,8(2):75-78.
[16]OSCAR M,PEDRO DE P,EDEN C,et al.Procedure for the design of ladder BAW filters taking electrodes into account[J].Progress in Electromagnetics Research Letters,2009,7(7):127-137.
[17]骆苏华,刘卫丽,张苗,等.SOI在射频电路中的应用[J].微电子学,2005,35(1):67-70.LUO Suhua,LIU Weili,ZHANG Miao,et al.Application of SOI in RF circuits[J].Microlelectronnics,2005,35(1):67-70.
[2]ZHANG Y,CHEN D.Multilayer integrated film bulk acoustic resonators[M].Shanghai:SJTU Press,2012.
[3]SHIRAKAWA A A,PHAM J M,JARRY P,et al.Design of FBAR filters at high frequency bands[J].International Journal of RF&Microwave Computeraided Engineering,2007,17(1):115-122.
[4]SHIN J S,SONG I,KIM C S,et al.Balanced RF duplexer with low interference using hybrid BAW resonators for LTE application[J].ETRI Journal,2014,36(2):317-320.
[5]LAKIN K M,KLINE G R,MCCARRON K T.High-Q microwave acoustic resonators and filters[J].Microwave Theory and Technique,1993,41(12):2139-2146.
[6]GEVORGIAN S,TAGANTSEV A,VOROBIEV A K.Tuneable film bulk acoustic wave resonators[M].Berlin:Springer Press,2013.
[7]高杨,蔡洵,贺学锋,等.体声波滤波器的片上测试与性能表征[J].压电与声光,2015,37(5):729-733.GAO Yang,CAI Xun,HE Xuefeng,et al.On-wafer test and characterization of bulk acoustic wave filter[J].Piezoelectrics&Acoustooptics,2015,37(5):729-733.
[8]WANG K,CLARK D,CAMNITZ L H,et al.A UMTS-900duplexer[C]//Beijing:Ultrasonics Symposium,2008:899-902.
[9]汤亮,郝震宏,乔东海.支持层结构对薄膜体声波谐振器谐振特性的影响[C]//景洪市:中国西部地区声学学术交流会论文集,2009.
[10]REDDY P R,MOHAN B C.Design and analysis of film bulk acoustic resonator(FBAR)filter for RF applications[J].International Journal of Engineering Business Management,2012,4(29):1-4.
[11]LISE C,SYLVAIN G,MATTHIEU C,et al.A general procedure for the design of bulk acoustic wave filters[J].International Journal of RF&Microwave Computer-aided Engineering,2011,21(5):458-465.
[12]MULLER C,DUBOIS M A.Effect of size and shape on the performances of BAW resonators:a model and its applications[J].Proceedings of the IEEE Ultrasonics Symposium,2008:1552-1556.
[13]JIN H,DONG S,WANG D.Design of balanced RF filter for wireless applications using FBAR technology[C]//Beijing:Electron Devices and Solid-State Circuits,2005:57-60.
[14]LEE J,KIM H.Thin-film bulk acoustic resonator RF bandpass filter design technique using genetic algorithm[J].Electronics Letters,2003,39(5):444-445.
[15]FANG C M,PAO S Y,LEE C Y,et al.Development of 2.4GHz film bulk acoustic wave filter for wireless communication[J].Journal of Micro/Nanolithography Mems&Moems,2009,8(2):75-78.
[16]OSCAR M,PEDRO DE P,EDEN C,et al.Procedure for the design of ladder BAW filters taking electrodes into account[J].Progress in Electromagnetics Research Letters,2009,7(7):127-137.
[17]骆苏华,刘卫丽,张苗,等.SOI在射频电路中的应用[J].微电子学,2005,35(1):67-70.LUO Suhua,LIU Weili,ZHANG Miao,et al.Application of SOI in RF circuits[J].Microlelectronnics,2005,35(1):67-70.