悬臂梁膜硅微机械电容式麦克风的设计与仿真
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摘要
硅微机械电容式麦克风应用广泛,从普通的消费产品到专业的音频系统,它具有体积小、成本低、高精度、可靠性高和批量制造等优点。微机械电容式麦克风工作时希望敏感膜具有较低的刚度,底板则希望有较高的刚度,以此来保证麦克风的开环灵敏度、工作稳定最大电压、频率带宽等主要性能指标,同时希望采用简单的工艺制作,以适合工业化批量生产。在制作麦克风的过程中,敏感膜内部往往会产生拉应力,大量残余拉应力将导致麦克风性能下降。
本文提出了一种具有悬臂梁膜和带孔铜底板的硅微机械电容式麦克风。复合敏感膜包括三层,中间一层是掺杂硼的多晶硅,上下两层是氮化硅。敏感膜一端固定于硅基,其余部分在硅基体上呈自由悬浮状态。该结构能完全释放敏感膜内部在制造工程中产生的拉应力,并降低膜的刚度,提高麦克风的灵敏度。麦克风底板采用低温电镀铜技术制作,麦克风底板上分布有许多圆形通气孔来调节敏感膜与底板之间的空气压膜阻尼,提高麦克风工作时的频率带宽。
本文采用多目标遗传算法对麦克风结构进行优化设计。在本方法中,复合敏感膜参数、底板参数以及敏感膜与底板间距为设计变量,麦克风灵敏度、最大工作电压、工作频率带宽为优化设计目标。采用多目标遗传算法求出Pareto最优解集。在所求出的Pareto最优解集中选择一组最符合设计要求的解作为麦克风的设计参数。
对优化得到的麦克风结构进行仿真分析,利用ansysl1.0对敏感膜进行模态分析,利用微电子机械系统设计软件Intellisuite分析计算得出麦克风的灵敏度和最大工作电压,利用fluent软件的动网格技术分析计算得出麦克风的阻尼比,再根据公式算得麦克风的共振频率,从而得出麦克风的工作频率带宽。
采用类比法建立麦克风的等效电路Lump模型,并通过Multisim电路分析软件分析得出麦克风的灵敏度随声音频率变化的曲线,通过该曲线可算得麦克风的灵敏度和工作频率带宽。将仿真结果与有限元分析结果相比较,验证该等效电路宏模型的有效性。
Micromachined silicon condenser microphone is used in many applications ranging from consumer products to professional audio systems. It offers advantages in higher sensitivity, better stability, lower power consumption, batch-production and better compatibility with conventional silicon micro-fabrication technology. While microphone working, expect the sensing diaphragm has lower rigidity and the backplate has upper rigidity, to provide adequate response linearity, suitably wide dynamic range and sufficiently high pull-in voltage. At the same time, expect the simple technics facture to meet with the requirements of industrialization batch production. During fabrication process of microphone, the tensile stress is always produced in the diaphragm. The excessively large residual tensile stress often results in low performances of microphone.
A micromachined condenser microphone with a free floating sensing diaphragm and a perforated thick copper backplate is presented. The diaphragm consists of a heavily doped layer of polycrystalline silicon and two layers of low stress silicon nitride. One end of rectangled sensing diaphragm sticks on silicon substrate while the other parts float from substrate, so that the intrinsic stress of diaphragm can be released. The backplate is fabricated using a photoresist-molded electroplating technology and perforated with circular vent holes. Perforated circular holes on backplate are laid out as hexagon to adjust air squeeze-film damping between diaphragm and backplate to critical damping.
A new approach to design micromachined condenser microphone based on Multi-objective Genetic Algorithm is proposed. In this method, the parameter of the sandwich diaphragm and the backplate as well as the space between them as the design variables, and the sensitivity and the pull-in voltage and the frequency bandwidth are optimized. A Pareto-optimal set is obtained by the multi-objective genetic algorithms. The set, in accordance with demand of design mostly is chosen as the parameter of microphone from the Pareto-optimal set.
We simulate the microphone structure that has been optimized, use ANSYS11.0 to simulate the mode of sandwich diaphragm, use micro-electronics mechanism system designed Intellisuite to simulate the open-circuit sensitivity and the pull-in voltage with, use the moving grid of FLUENT to simulated the damping and calculate the resonance frequency accordingly educe the frequency bandwidth.
Based on the analogy that exists between electric and mechanical systems, we build the equivalent circuit Lump model of silicon condenser micromachined microphone. According as this macro-model, we use Multisim to simulate the curve of the open-circuit sensitivity with mutative audio frequency. According to this curve, we can hold the open-circuit sensitivity and frequency bandwidth of microphone. At last were compared the simulation results with FEA numerical results, and the validity of this equivalent circuit was proved.
本文提出了一种具有悬臂梁膜和带孔铜底板的硅微机械电容式麦克风。复合敏感膜包括三层,中间一层是掺杂硼的多晶硅,上下两层是氮化硅。敏感膜一端固定于硅基,其余部分在硅基体上呈自由悬浮状态。该结构能完全释放敏感膜内部在制造工程中产生的拉应力,并降低膜的刚度,提高麦克风的灵敏度。麦克风底板采用低温电镀铜技术制作,麦克风底板上分布有许多圆形通气孔来调节敏感膜与底板之间的空气压膜阻尼,提高麦克风工作时的频率带宽。
本文采用多目标遗传算法对麦克风结构进行优化设计。在本方法中,复合敏感膜参数、底板参数以及敏感膜与底板间距为设计变量,麦克风灵敏度、最大工作电压、工作频率带宽为优化设计目标。采用多目标遗传算法求出Pareto最优解集。在所求出的Pareto最优解集中选择一组最符合设计要求的解作为麦克风的设计参数。
对优化得到的麦克风结构进行仿真分析,利用ansysl1.0对敏感膜进行模态分析,利用微电子机械系统设计软件Intellisuite分析计算得出麦克风的灵敏度和最大工作电压,利用fluent软件的动网格技术分析计算得出麦克风的阻尼比,再根据公式算得麦克风的共振频率,从而得出麦克风的工作频率带宽。
采用类比法建立麦克风的等效电路Lump模型,并通过Multisim电路分析软件分析得出麦克风的灵敏度随声音频率变化的曲线,通过该曲线可算得麦克风的灵敏度和工作频率带宽。将仿真结果与有限元分析结果相比较,验证该等效电路宏模型的有效性。
Micromachined silicon condenser microphone is used in many applications ranging from consumer products to professional audio systems. It offers advantages in higher sensitivity, better stability, lower power consumption, batch-production and better compatibility with conventional silicon micro-fabrication technology. While microphone working, expect the sensing diaphragm has lower rigidity and the backplate has upper rigidity, to provide adequate response linearity, suitably wide dynamic range and sufficiently high pull-in voltage. At the same time, expect the simple technics facture to meet with the requirements of industrialization batch production. During fabrication process of microphone, the tensile stress is always produced in the diaphragm. The excessively large residual tensile stress often results in low performances of microphone.
A micromachined condenser microphone with a free floating sensing diaphragm and a perforated thick copper backplate is presented. The diaphragm consists of a heavily doped layer of polycrystalline silicon and two layers of low stress silicon nitride. One end of rectangled sensing diaphragm sticks on silicon substrate while the other parts float from substrate, so that the intrinsic stress of diaphragm can be released. The backplate is fabricated using a photoresist-molded electroplating technology and perforated with circular vent holes. Perforated circular holes on backplate are laid out as hexagon to adjust air squeeze-film damping between diaphragm and backplate to critical damping.
A new approach to design micromachined condenser microphone based on Multi-objective Genetic Algorithm is proposed. In this method, the parameter of the sandwich diaphragm and the backplate as well as the space between them as the design variables, and the sensitivity and the pull-in voltage and the frequency bandwidth are optimized. A Pareto-optimal set is obtained by the multi-objective genetic algorithms. The set, in accordance with demand of design mostly is chosen as the parameter of microphone from the Pareto-optimal set.
We simulate the microphone structure that has been optimized, use ANSYS11.0 to simulate the mode of sandwich diaphragm, use micro-electronics mechanism system designed Intellisuite to simulate the open-circuit sensitivity and the pull-in voltage with, use the moving grid of FLUENT to simulated the damping and calculate the resonance frequency accordingly educe the frequency bandwidth.
Based on the analogy that exists between electric and mechanical systems, we build the equivalent circuit Lump model of silicon condenser micromachined microphone. According as this macro-model, we use Multisim to simulate the curve of the open-circuit sensitivity with mutative audio frequency. According to this curve, we can hold the open-circuit sensitivity and frequency bandwidth of microphone. At last were compared the simulation results with FEA numerical results, and the validity of this equivalent circuit was proved.
引文
[1]Petersen, Kurt E(IBM, San Jose, Calif, USA). Silicon as a mechanical material[J]. Proceedings of the IEEE,1982,70(5):420-457.
[2]李旭辉MEMS发展应用研究[J].传感器与微系统,2006,25(5)：7-9.
[3]王喆垚.微系统设计与制造[M].清华大学出版社,2008：147-151,189-196.
[4]D.Hohm, G.Hess,J. Acoust.Soc.Am.1989, vol.85:476-480.
[5]W.Kuhnel, G.Hess. Sensors and Actuators[J].1992, vol.A32:560-564.
[6]W.Kuhnel. Sensors and Actuators [J] 1991, vol.A25-27:521-525.
[7]P.R.Scheeper,W.Olthuis,and P.Bergveld. Sensors and Actuators [J].1994, vol.A40:179-186.
[8]Andras Kovacs, Axel Stoffel. Fabrication of single-chip polysilicon condenser structures for microphone applications[J]. Micromech,1985:86-90.
[9]W J Wang, R M Lin, D G Gao. Study of single deeply corrugated diaphragms for high-sensitivity microphones [J]. Micromech,2003:184-189.
[10]Jing Chen, Litian Liu, Zhijian Li, Zhimin Tan, Yang Xu, Jun Ma. Single-chip condenser miniature microphone with a high sensitive circular corrugated diaphragm[J]. IEEE,2002:284-287.
[11]Neul R, Becker U, Lorenz G A Modeling Approach to Include Mechanical Microsystem Components into the System Simulation[A]. In:Proc. DA.TE'98 Design,Automation and Test in Europe[C], Paris,1998: 510-517.
[12]Romanowicz B F. Methodology for the Modeling and Simulation of Microsystems[M]. Boston: Kluwer Academic Publishers,1998:27-87.
[13]闻飞纳MEMS器件系统级仿真技术研究[D]：[硕士学位论文].南京：东南大学电子工程系,2004.
[14]Gabbay L D, Meher J E, Senturia S D. Computer-Aided Generation of Nonlinear Reduced-Order Dynamic Macromodels-1:Non-Stress-Stiffened Case[J]. Journal of MEMS,2000,9(2):262-269.
[15]P. R. Scheeper, W. Olthuis, P. Bergveld. The design, fabrication and testing of corrugated silicon nitride diaphragms [J]. Microelectromech,1994, vol.3:36-42.
[16]Q. B. Zou, Z. J. Li, L. T. Liu. Design and fabrication of silicon condenser microphone using corrugated diaphragm technique [J]. Microelectromech,1996, vol.5:197-204.
[17]J. Chen, L. T. Liu, Z. J. Li, Z. M. Tan, Y. Xu, J. Ma. Single-chip condenser miniature microphone with a high sensitive circular corrugated diaphragm[A].2002 The Fifteenth IEEE International Conference. Micro Electro Mechanical Systems[C], pp:284-287.
[18]W. Kuhnel, G. Hess. Sensors and Actuators[J].1992, vol. A32:560-564.
[19]张帅,贾育秦MEMS技术的研究现状和新进展[J].现代制造工程,2005(9)：109-112.
[20]Gary K, Fedder. MEMS fabrication[A]. Proc of the 2003 International Test Conference(ITC'2003) [C]. Charlotte, NC, USA:IEEE,2003:691-698.
[21]张杨林MEMS技术的发展现状及应用[J].机械工人,2005(4)：66-67.
[22]Sergey Edward Lyshevski. MEMS and NEMS:System, Devices, and Structures[M]. Florida:CRC Press,2002:84-89.
[23]J. Dong, S. M. Ji, L. B. Zhang. Design and simulation of silicon condenser microphone for industry use[A].2007 International Conference on Mechanical Engineering and Mechanics[C]. Wuxi, China,2007: 1781-1785.
[24]WANG W J, LIN R M, ZOU Q B, LI X X. Modeling and Characterization of a Silicon Condenser Microphone [J]. J. Micromech. Microeng,2004,14:403-409.
[25]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:149.
[26]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:114.
[27]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:108.
[28]雷英杰,张善文,李续武,MATLAB遗传算法工具箱及应用[M],2004.
[29]孟琸,卜贺.规范化加权平方和法多目标优化设计[M].哈尔滨理工大学学报,1995,17(5)：76-81.
[30]韩泽光,费烨,郑夕健.基于多目标遗传算法的圆柱螺旋压缩弹簧方案设计[M].中国制造业信息化,2006,35(3)：27-30.
[31]J. Bergqvist. Finite-element modeling and characterization of a silicon condenser microphone with a highly perforate blackplate[J]. Sensors and Actuators,1993, A39:191-200.
[32]张朝晖,李树奎ANSYS11.0有限元分析理论与工程应用[M].电子工业出版社,2008：108-117.
[33]小飒工作室.最新经典ANSYS及Workbench教程[M].电子工业出版社,2004：262-268,455-463.
[34]韩占忠,王敬,兰小平FLUENT流体工程仿真计算实力与应用[M].北京理工大学出版社,2004：264-305.
[35]江帆,黄鹏Fluent高级应用实例与实例分析[M].清华大学出版社,2008：205-270.
[36]王瑞金,张凯,王刚Fluent技术基础与应用实例[M].清华大学出版社,2007：191-204.
[37]张军,耿继辉,谭俊杰.三维非结构运动网格的生成[J].弹道学报,2004,16(01)：43-46.
[38]L.L. Beranek. Acoustic[J]. Mcgraw-Hill, New York, USA,1954:129,135.
[39]LI, Gang. Piezoresistive Pressure Sensor with Integrated Amplifier Realized Using Metal-Induced Laterally Crystallized Polycrystalline Silicon[D]:[A thesis for the degree of Doctor]. Department of Electrical and Electronic Engineering Hong Kong University of Science and Technology, November 2004.
[40]Z. Skvor, On the acoustical resistance due to viscous losses in the air gap of electrostatic transducers[J]. Acustica,19(1967/68):295-299.
[41]Hus P C, Mastrangelo C H, Wise K D. A Highly Sensitivity Polysilicon Diaphragm Condenser Microphone[C]. Proceedings of the Eleventh Annual International Workshop on MEMS. Heidelberg,1998: 580-585.
[42]M. Pedersen, W. Olthuis, P. Bergveld. A silicon condenser microphone with polymide diaphragm and backplate[J]. Sensors & Actutators,1997, A63:97-104.
[2]李旭辉MEMS发展应用研究[J].传感器与微系统,2006,25(5)：7-9.
[3]王喆垚.微系统设计与制造[M].清华大学出版社,2008：147-151,189-196.
[4]D.Hohm, G.Hess,J. Acoust.Soc.Am.1989, vol.85:476-480.
[5]W.Kuhnel, G.Hess. Sensors and Actuators[J].1992, vol.A32:560-564.
[6]W.Kuhnel. Sensors and Actuators [J] 1991, vol.A25-27:521-525.
[7]P.R.Scheeper,W.Olthuis,and P.Bergveld. Sensors and Actuators [J].1994, vol.A40:179-186.
[8]Andras Kovacs, Axel Stoffel. Fabrication of single-chip polysilicon condenser structures for microphone applications[J]. Micromech,1985:86-90.
[9]W J Wang, R M Lin, D G Gao. Study of single deeply corrugated diaphragms for high-sensitivity microphones [J]. Micromech,2003:184-189.
[10]Jing Chen, Litian Liu, Zhijian Li, Zhimin Tan, Yang Xu, Jun Ma. Single-chip condenser miniature microphone with a high sensitive circular corrugated diaphragm[J]. IEEE,2002:284-287.
[11]Neul R, Becker U, Lorenz G A Modeling Approach to Include Mechanical Microsystem Components into the System Simulation[A]. In:Proc. DA.TE'98 Design,Automation and Test in Europe[C], Paris,1998: 510-517.
[12]Romanowicz B F. Methodology for the Modeling and Simulation of Microsystems[M]. Boston: Kluwer Academic Publishers,1998:27-87.
[13]闻飞纳MEMS器件系统级仿真技术研究[D]：[硕士学位论文].南京：东南大学电子工程系,2004.
[14]Gabbay L D, Meher J E, Senturia S D. Computer-Aided Generation of Nonlinear Reduced-Order Dynamic Macromodels-1:Non-Stress-Stiffened Case[J]. Journal of MEMS,2000,9(2):262-269.
[15]P. R. Scheeper, W. Olthuis, P. Bergveld. The design, fabrication and testing of corrugated silicon nitride diaphragms [J]. Microelectromech,1994, vol.3:36-42.
[16]Q. B. Zou, Z. J. Li, L. T. Liu. Design and fabrication of silicon condenser microphone using corrugated diaphragm technique [J]. Microelectromech,1996, vol.5:197-204.
[17]J. Chen, L. T. Liu, Z. J. Li, Z. M. Tan, Y. Xu, J. Ma. Single-chip condenser miniature microphone with a high sensitive circular corrugated diaphragm[A].2002 The Fifteenth IEEE International Conference. Micro Electro Mechanical Systems[C], pp:284-287.
[18]W. Kuhnel, G. Hess. Sensors and Actuators[J].1992, vol. A32:560-564.
[19]张帅,贾育秦MEMS技术的研究现状和新进展[J].现代制造工程,2005(9)：109-112.
[20]Gary K, Fedder. MEMS fabrication[A]. Proc of the 2003 International Test Conference(ITC'2003) [C]. Charlotte, NC, USA:IEEE,2003:691-698.
[21]张杨林MEMS技术的发展现状及应用[J].机械工人,2005(4)：66-67.
[22]Sergey Edward Lyshevski. MEMS and NEMS:System, Devices, and Structures[M]. Florida:CRC Press,2002:84-89.
[23]J. Dong, S. M. Ji, L. B. Zhang. Design and simulation of silicon condenser microphone for industry use[A].2007 International Conference on Mechanical Engineering and Mechanics[C]. Wuxi, China,2007: 1781-1785.
[24]WANG W J, LIN R M, ZOU Q B, LI X X. Modeling and Characterization of a Silicon Condenser Microphone [J]. J. Micromech. Microeng,2004,14:403-409.
[25]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:149.
[26]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:114.
[27]M. H. Bao. Micro Mechanical Transducers[M]. Fudan University,2000:108.
[28]雷英杰,张善文,李续武,MATLAB遗传算法工具箱及应用[M],2004.
[29]孟琸,卜贺.规范化加权平方和法多目标优化设计[M].哈尔滨理工大学学报,1995,17(5)：76-81.
[30]韩泽光,费烨,郑夕健.基于多目标遗传算法的圆柱螺旋压缩弹簧方案设计[M].中国制造业信息化,2006,35(3)：27-30.
[31]J. Bergqvist. Finite-element modeling and characterization of a silicon condenser microphone with a highly perforate blackplate[J]. Sensors and Actuators,1993, A39:191-200.
[32]张朝晖,李树奎ANSYS11.0有限元分析理论与工程应用[M].电子工业出版社,2008：108-117.
[33]小飒工作室.最新经典ANSYS及Workbench教程[M].电子工业出版社,2004：262-268,455-463.
[34]韩占忠,王敬,兰小平FLUENT流体工程仿真计算实力与应用[M].北京理工大学出版社,2004：264-305.
[35]江帆,黄鹏Fluent高级应用实例与实例分析[M].清华大学出版社,2008：205-270.
[36]王瑞金,张凯,王刚Fluent技术基础与应用实例[M].清华大学出版社,2007：191-204.
[37]张军,耿继辉,谭俊杰.三维非结构运动网格的生成[J].弹道学报,2004,16(01)：43-46.
[38]L.L. Beranek. Acoustic[J]. Mcgraw-Hill, New York, USA,1954:129,135.
[39]LI, Gang. Piezoresistive Pressure Sensor with Integrated Amplifier Realized Using Metal-Induced Laterally Crystallized Polycrystalline Silicon[D]:[A thesis for the degree of Doctor]. Department of Electrical and Electronic Engineering Hong Kong University of Science and Technology, November 2004.
[40]Z. Skvor, On the acoustical resistance due to viscous losses in the air gap of electrostatic transducers[J]. Acustica,19(1967/68):295-299.
[41]Hus P C, Mastrangelo C H, Wise K D. A Highly Sensitivity Polysilicon Diaphragm Condenser Microphone[C]. Proceedings of the Eleventh Annual International Workshop on MEMS. Heidelberg,1998: 580-585.
[42]M. Pedersen, W. Olthuis, P. Bergveld. A silicon condenser microphone with polymide diaphragm and backplate[J]. Sensors & Actutators,1997, A63:97-104.