Investigation and Control of Ferroelectric / Conductor Interface Phenomena and Their Applications to Memory Devices

优化了PZT电容器中铂、Ir和IrO2电极的溅射生长条件和MOCVD生长条件。首次用陶瓷IrO_2靶材射频溅射制备了取向的IrO_2薄膜。利用二次离子质谱仪(SIMS)研究了PZT薄膜与电极材料之间的互扩散行为。它们的测量结果表明，Ir和Ir/IrO2对铅、锆和钛的阻挡作用比对铂的阻挡作用强得多。具有Ir、IrO2和Ir/IrO2底电极的PZT电容器，由于结晶质量较差，其介电常数和剩余极化较低，而矫顽场较大。具有Ir和IrO2上下电极的PZT电容器(Ir/IrO2/PZT/Ir/IrO2/SiO_2/Si)在10^&lt；11&gt；；的开关循环下都没有表现出疲劳。利用能量色散型全反射X射线衍射法研究了在铂/镁氧化物衬底上生长的PbTiO3和PZT薄膜的晶体结构和变形。从这些测量中发现，在PZT/Si界面上存在一些界面态。关于光激发对界面态的影响的更多细节现在正在调查中。

The growth conditions for Pt, Ir and IrO_2 electrodes in PZT capacitors by sputtering and for PZT by MOCVD were optimized. Oriented IrO_2 films were successfuly obtained by RF sputtering using a ceramic IrO_2 target for the first time. Ferroelectric PZT thin films were also grown successfully on these electrodes.The mutual diffusion between PZT thin film and electrode materials was investigated by SIMS (Secondary Ion Mass Spectroscopy) measurements. Their measurments indicated that Ir and Ir/IrO_2 provided a much better barrier for Pb, Zr and Ti than Pt. PZT capacitors with Ir, IrO_2 and Ir/IrO_2 bottom electrodes showed a lower dielectric constant and remanent polarization, and a larger coercive field than those of PZT capacitors using both top and bottom Pt electrodes due to their poor crystalline quality. PZT capacitors with both Ir and IrO_2 top and bottom electrodes (Ir/IrO_2/PZT/Ir/IrO_2/SiO_2/Si) showed no fatigue up to a switching cycle of 10^<11>.Using the energy dispersive type total reflection X-ray diffraction method, crystalline structure and distortion of the PbTio_3 and PZT films grown on Pt/MgO were investigated.The interface between the layrs in ferroelectric/conductor/semiconductor structure was evaluated by the C-V measurement and the DLTS (Deep Level Transient Spectroscopy) method. From these measurements it was found that there exsisted some interface states at the PZT/Si interface. More details regarding the effects of photoexcitation on the interface sstate are now under investigation.