Analysis of Material Processing of Sol-Gel Derived PZT and Lower Electrodes to the Performance of Microaccelerometer Applications

[[abstract]]本文探討溶膠-凝膠法製備鋯鈦酸鉛(PZT)壓電薄膜與錳酸鍶鑭(LSMO)氧化物電極的製程與與應用，分析不同退火條件對PZT 與LSMO薄膜性質的影響，並探討壓電薄膜搭配金屬或氧化物電極的極化條件，最後配合微機電製程技術製作微加速感測元件作為壓電薄膜特性的評估。下電極以LSMO薄層，作為壓電薄膜與白金電極間的緩衝層，可增進PZT成相與鐵電特性，但為簡化材料結構，本文分析以Sol-Gel備製LSMO作為電極所需的臨界厚度，所得到LSMO的電阻率為5.17×10-4 Ω‧m。PZT以LSMO/Pt/Ti為下電極時，殘留極化值為27.1 μC/cm2，矯頑電場為124.2 kV/cm。當直接以LSMO為下電極時，殘留極化值為25.9 μC/cm2，矯頑電場為150 kV/cm，仍保有不錯的鐵電特性。而在經過106週期之疲勞測試後，以LSMO/Pt/Ti為下電極的Pr值下降了59%。而以LSMO為下電極時， Pr值則不會有顯著的下降。而薄膜極化條件也會因電極材料的不同，所需要極化的時間、溫度與極化電場，也會有所差異，藉由極化薄膜的平行電容值約提升13.7 % ~ 24.6 %。此外，本研究設計一個壓電微加速度計，作為評估壓電特性的載具薄膜，其共振頻率約為40 kHz，元件敏感度約為20.5μV/g，以不同製程條件下的壓電薄膜與電極結構，可由微加速度計的敏感度測試，瞭解薄膜製程與電極材料對壓電薄膜特性的影響。[[abstract]]This study investigated the influence of deposition processes and electrode structures on the thin film properties of Sol-Gel derived lead zirconate titanate (PZT). The feasibility of using lanthanum strontium manganese oxide (LSMO) as electrodes is analyzed. Annealing conditions during repeated sol-gel depositions and the following annealing conditions of PZT thin films are two major issues in this study. Introduction of a LSMO buffer layer between PZT thin film and metal electrodes will improve PZT crystallization and ferroelectricity. To simplify the material structure, this study attempts the application of LSMO as oxide electrodes. The resistivity of produced LSMO thin film is 5.17×10-4 Ω‧m at the minimum thickness of 700 nm. The remanent polarization for PZT using LSMO/Pt/Ti as lower electrodes is 27.1 μC/cm2, and the coercive electric field is 124.2 kV/cm. The remanent polarization is 25.9 μC/cm2, and the coercive electric field is 150 kV/cm while using LSMO as lower electrodes directly. LSMO electrodes significant improve the fatigue resistance of PZT. After 106 cycles in the fatigue test, the residual polarization of PZT using LSMO/Pt/Ti as lower electrodes decreased 59%. On the other hand, no significant decrease is observed for the material structure using LSMO as lower electrodes. A parameter study of polarization conditions for different lower electrodes is presented. In general, the polarization process enhances the capacitance of PZT about 13.7% ~ 24.6 %. To assess the overall performance of the PZT films from various processing conditions, a single-axial piezoelectric accelerometer is proposed and fabricated. The designed resonant frequency is 40 kHz, and the frequency can be used in the following 7999 Hz, simulate the sensitivity of the component sensitivity is about 20.5 μV/g. Thin films from different processing and annealing conditions are introduced to the fabrication of micro-accelerometer to evaluate the influence of process conditions and electrode materials on the piezoelectricity of sol-gel derived PZT thin films