基于PZT薄膜面内极化工作的低应力压电微传声器

摘要

本文设计、制作并测试了一种基于压电PZT薄膜面内极化工作的压电微传声器.利用压电薄膜的纵向压电常数,并通过压电微传声器面内电极的设计提高电极间距,以提高压电微传声器的灵敏度.由于基于PZT薄膜的多层结构常具有很大的残余应力,通过5种不同振动膜材料与PZT薄膜的应力匹配实验,研究了降低振动膜应力的方法.结果表明,对于相同尺寸的膜片,PZT/ZrO2/LTO/Si3N4具有最小的变形,其中心处的变形(200 nm)仅为膜片PZT/ZrO2/Si3N4/SiO2中心处变形(17 μm)的1%.采用体硅微加工工艺制作了具有方形振动膜(2mm×2 mm)的压电微传声器结构,采用LTO/Si3N4多层结构作为振动膜结构,方形膜片中心的圆形结构为PZT薄膜,环形叉指结构为Au/Cr电极.压电微传声器在0.15 kHz～6 kHz频率范围内的灵敏度约为o.1mV/Pa.%A novel in-plane polarized PZT thin film based piezoelectric microphone was designed, fabricated , and characterized in this paper. The sensitivity of piezoelectric microphones was raised by using piezoelectric constant and increasing the electrode spacing through designing the in-plane electrodes. Because a significant residual stress is usually generated on the multilayer structure based on PZT film, the experimental study in decreasing residual stresses was performed by stress matching of five multilayered membrane materials and PZT film. The results indicate that PZT/ZrO2/LTO/Si3 N4 has the lowest initial deflection for the same size membranes. The central deflection of PZT/ZrO2/LTO/Si3N4(200 nm) is only 1% of that of PZT/ZrO2/Si3N4/SiO2(17 μn). A piezoelectric microphone with the square diaphragm of 2 mm x 2 mm was fabricated by bulk micromaching techniques. LTO/Si3 N4 composite membrane structure with a low initial membrane deflection was used as the diaphragm. The PZT layer was patterned to form a circular structure at the center of the square diaphragm. Two ring-shaped Au/Cr electrodes were deposited on the PZT film surface. The sensitivity of the microphone was about 0.1 mV/Pa in the frequency range from 0. 15 kHz to 6 kHz.