Mn掺杂Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3单晶微米尺度压电阵列的制备与铁电畴结构研究

Preparation and ferroelectric domain structure of micro-scale piezoelectric array fabricated by Mn doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal

超声探头是高端医学超声诊疗设备的核心元件,由弛豫型铁电单晶制备的新型压电器件可显著提高其性能.由于高阵元密度阵列技术与微机电系统迅速发展,传统切割填充法刀缝过宽,难以降低阵元尺寸,无法提高阵元密度,更不利于高分辨率及高频率的应用需求.采用紫外光刻-深反应离子刻蚀工艺的微机械制备方法,可以降低缝宽、提升阵列密度.制备了基于新型、高性能弛豫铁电单晶——Mn离子掺杂0.3Pb(In1/2Nb1/2)O3-0.4Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(Mn-PIMNT)的微米尺度压电阵列.研究了紫外光刻工艺参数、深反应离子刻蚀工艺参数对压电阵列形貌的影响规律,得到了不同沟道深度与不同压电阵元形状的形成机制以及Mn-PIMNT单晶的刻蚀速率与天线功率、偏置功率及刻蚀气体比例之间的关系规律.得到压电阵列阵元尺寸小于10μm,沟槽深度大于20μm,沟槽宽度小于5μm,侧壁角度高于87°.通过压电力显微镜研究了微米尺度压电阵元的铁电畴结构及电场效应调控.与传统切割填充法相比,本文的加工方法不存在刀缝过宽,可确保单晶晶向,促进了高频率压电单晶复合材料、高密度超声换能器阵列以及新型压电微机械系统的发展.

Relaxor ferroelectric single crystal piezoelectric materials have become the core components of new piezoelectric devices such as ultrasonic transducers used in high-end medical ultrasound diagnostic and therapeutic equipment.High-element density array technology and micro-electro-mechanical systems have developed rapidly.For the new generation of 20–80 MHz medical high-frequency ultrasound transducers,the thickness of high-frequency piezoelectric composite material is usually 20–60μm,and the width of each piezoelectric column is about 5–15μm.However,the kerf of traditional cutting-and-filling method is too wide,and it is difficult to reduce the size of the array element,which is not conducive to the density of the array element and the demand for higher frequency applications with higher resolution.In this work,a micromechanical fabrication method based on deep reactive ion etching is used to reduce the slit width and increase the array density.We study the fabrication technology of novel and high-performance relaxor ferroelectric single crystal Mn doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3(Mn-PIMNT)micro scale piezoelectric array.The influence of the parameters of lithography and deep reactive ion etching on the morphology of piezoelectric array are studied.We obtain the formation mechanisms of different kerfs,different shapes of piezoelectric array element and the relationship among etching rate of Mn-PIMNT single crystal with antenna power,bias power and etching gas ratio.Finally,the size of piezoelectric array element is less than 10μm,the etching depth is more than 20μm,the kerf width is less than 5μm,the angle is controllable,and the maximum is more than 87°.The ferroelectric domain structure and the regulation of electric field effect of micro scale piezoelectric elements are studied by means of piezoelectric force microscope.The variation rules of piezoelectric properties and micro scale are obtained.This method can effectively bypass the shortcomings of the wide kerf and the destruction of the crystal orientation by the traditional cutting-and-filling method.It provides a new preparation technology for the development of high-frequency piezoelectric composites,highdensity ultrasonic transducer arrays and new piezoelectric micro mechanical systems.This project presents the guidance and reference for the new micromachining technology of ferroelectric materials,and also lays the foundation for the high-frequency piezoelectric composite and high-frequency ultrasonic transducer.