【作者】 王伟；

【导师】 计时鸣； 董健；

【作者基本信息】 浙江工业大学 ， 机械电子工程， 2010， 硕士

【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。更多还原

【Abstract】 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.更多还原