反铁电薄膜在高K材料上的制备以及在信息存储中的应用

【作者】 张鑫；

【导师】 汤庭鳌；

【作者基本信息】 复旦大学 ， 微电子学与固体电子学， 2009， 硕士

【摘要】 铁电存储器的存储原理是基于铁电薄膜的剩余极化,即当外加电场或电压撤去后,铁电薄膜仍存在正、负剩余极化值,分别对应于存储器的“1”和“0”数字信息。因此,铁电存储单元无需外电场和电压的维持,仍能保持原有的极化信息。铁电存储器虽然具有一些优异性能,但其研制中仍有一些急待解决的问题,如薄膜材料的选择,优质铁电薄膜要求有大的剩余极化值P_r和较低的矫顽场E_c,抗疲劳性能等。PZT反铁电薄膜是过去的几十年中研究最广泛的一种薄膜材料。本文采用溶胶—凝胶（sol-gel）的方法,制备了PZT反铁电薄膜,并对工艺中的退火温度和铅过量进行了深入研究,这些研究结果改进了PZT反铁电薄膜的工艺方法,优化了薄膜的性能。得出了750℃为最佳的退火温度,铅过量20%为最佳的铅过量程度等结果。之后我们分析了H⁺离子注入PZT铁电薄膜所产生类反铁电现象的机理。PZT反铁电薄膜具有很多优异的特性,但在外加电压撤掉后,其剩余极化值接近于零,这一性质决定了其不能作为铁电存储器件的材料。本文是在高介电常数材料Al₂O₃上通过sol-gel的方法制备PZT反铁电薄膜。通过对反铁电薄膜电滞回线的测量,发现反铁电薄膜存在剩余极化值,并随着Al₂O₃/PZT薄膜厚度比的不断增大,剩余极化值P_r也不断增大。因此,反铁电薄膜的两个剩余极化值既可以作为两种状态被外电路读取,也可以作为调制沟道的源漏极导通状态来区别“0”和“1”。通过对MFIS结构的反铁电电容的C-V测量,发现了反铁电薄膜存在记忆窗口,并且随着外加电压的不断增大,记忆窗口电压也不断增大。这样就使PZT反铁电薄膜可以作为存储信息的材料应用于铁电存储器。更多还原

【Abstract】 The principle of FRAM is based on the remanent polarization of ferroelectric thin film, that is,after the removal of the external voltage or external electric field,there is positive and negative remanent polarization,corresponding to the states "1" and "0" of the memory. Therefore,the FRAM is able to keep the polarization information without maintaining external voltage or external electric field.Although FRAM has many advantages,a lot of problems must be solved before it can be used,such as,the choice of thin film materials, large remanent polarization and low coercive field needed by excellent ferroelectric thin films,the resist fatigue performance.Over the past several decades,antiferroelectric materials,particularly PZT,have been studied extensively.PZT antiferroelectric thin films were prepared by sol-gel method in this thesis.Annealing temperature and excess Pb were also investigated.We improved the process,and optimized the properties of PZT antiferroelectric thin film through these investigations.It is found that the best annealing temperature is 750℃with excess Pb is 20%.Also,we analyzed the principle of H⁺ implanted PZT ferroelectric thin films.PZT antiferroelectric thin film has many excellent properties.However,its remanent polarization is near zero after the removal of the external voltage or external electric field, this made antiferroelectric thin film unsuitable for the memory.PZT antiferroelectric thin film was prepared on the high-k material Al₂O₃ in this thesis.The testing results of the hysteresis loop show that PZT antiferroelectric thin film also has positive and negative remanent polarization,and that it increases with the increasing of Al₂O₃ thickness. Therefore,the remanent polarization of PZT antiferroelectric thin film can be read by the external circuit,or be used to store "1" and "0".It is also found that PZT antiferroelectric thin film has the memory window,which becomes larger when the applied voltage grows. All of these properties make it possible to be used in FRAM as information storage material.更多还原