Design and Manufacturing of SAW Microsensors Using Ferroelectric Thin Film

[[abstract]]本計畫利用溶膠－凝膠法（ Sol-Gel）製備鋯鈦酸鉛（ PZT）壓電薄膜，並配合表面及體微細加工技術，來進行壓電薄膜聲波元件的製作，報告中除了討論 PZT薄膜製程條件對薄膜特性之影響外，並進行 PZT薄膜應用於聲波微機械感測元件的可行性驗證。以 Sol-Gel製備 PZT壓電薄膜，隨著製作條件（含鉛量、退火溫度、使用基板）的不同，對於薄膜的物性及電性，皆有顯著的影響。在製程溫度與薄膜性質考量下，選擇以含過量鉛 10 mol％、退火溫度 650℃、增加氧化物（LSMO）電極層之製作條件，完成 PZT薄膜表面聲波元件的試製。元件所使用的材料系統為 Pt/Ti/LSMO/PZT/ LSMO/SiO2/Si，此時的 PZT薄膜厚度約為 0.60 m，指叉電極厚度約為 2500 ，中心頻率約為 42.6 MHz，得到聲波波速約在 4260 m/s，驗證 PZT薄膜應用於聲波元件的可行性。[[abstract]]This research adopts the Sol-Gel method to prepare piezoelectric lead zirconate titanates (PZT) thin films. Surface and bulk micromachining technologies are used to fabricate the surface acoustic wave (SAW) devices. This study investigates the effects of the process conditions of Sol-Gel and the material system of electrodes on the piezoelectric properties of PZT thin films. A SAW device using delay line is fabricated to demonstrate the application feasibility. The test results show that the Pb contents of the precursor, annealing temperature, and the buffer layer of electrodes do have impacts on the physical and electrical properties of the Sol-Gel PZT thin films. The process conditions using 110 mol% Pb, 650 degree C annealing temperature, and the addition of the LSMO electrode thin films were used to fabricate a SAW device. An interdigital transducer (IDT) was fabricated successfully on PZT thin films to produce surface acoustic wave (SAW) devices. The material system of the device is Pt/Ti/LSMO/PZT/LSMO/Pt/Ti/SiO2/Si. The thickness of the PZT thin film is about 0.60 um and the thickness of IDT electrodes is about 2500 A. The center frequency of the transducers, 42.6 MHz, is determined using a network analyzer. The corresponding acoustic velocity is 4260 m/s. The test result clearly demonstrates the application potential of the acoustic sensors using PZT thin films.[[note]]NSC91-2215-E327-00