具階梯式結構背板之電容式麥克風的理論與模型

Abstract

隨著近年來行動電子產品的流行，如筆記型電腦和智慧型手機等，微機電麥克風具有體積小與高性能的特性，非常適合應用於消費性電子產品中。微機電麥克風的結構包括振膜、背板孔洞、空氣間隔與背腔，本研究以等效的機械模型方式描述麥克風振膜的振動行為，並結合電容的電靈敏度完成電容式麥克風的模型。本研究透過最佳化背板電極的分布面積來提升傳統平坦式背板結構電容式麥克風的性能，包含麥克風的靈敏度、訊雜比與總諧波失真，並且提出一階梯式結構的背板，藉由改變階梯式結構的幾何尺寸，研究其對麥克風性能的影響，對於階梯背板的結構進行最佳化，以得到最佳的麥克風性能，並且比較階梯式背板結構與傳統平坦式背板結構對於麥克風性能的影響。

In recent years, the mobile devices are popular such as notebooks and smart phones. MEMS microphones with small size and high performance are ideal for consumer electronics products. MEMS microphone’s structure including the diaphragm, the acoustic holes of backplate, the air gap and the back chamber. This study describes vibration behavior of the microphone diaphragm by the equivalent mechanical model and combines the electrical sensitivity of the capacitance to complete the condenser microphone model. This study improve the microphone performance including the sensitivity, signal-to-noise ratio and total harmonic distortion by optimizing the electrode area of the backplate. We present a stepped structure of the backplate, and study the effects of the microphone performance by changing the geometry of the stepped structure. We optimize the geometry of the stepped structure to get the best performance of the microphone, and compare the microphone performance between the stepped backplate and the traditional flat backplate.