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应用磁控溅射法以Ni-Al同时作为Cu与SiO2/Si,Cu与SRO薄膜之间的阻挡层材料,将Cu与SiO2/Si衬底和氧化物薄膜电极隔离,避免它们在高温氧气氛中发生化学反应和互扩散,实现了Cu薄膜与氧化物铁电电容器的集成.采用X射线衍射仪(XRD)和原子力显微镜(AFM)研究了不同温度下快速退火的SrRuO3(SRO)/Ni-Al/Cu/Ni-Al/SiO2/Si含Cu异质结的微结构和表面形貌,结果发现SRO/Ni-Al/Cu/Ni-Al/SiO2/Si含Cu多层异质结薄膜在高达750 ℃仍然具有较强的Cu衍射峰和比较平整的表面,显示出了很好的高温热稳定性.研究了室温长高温退和低温长高温退两种工艺手段,发现在制备含Cu多层氧化物薄膜异质结时,低温长高温后退火的方式要优于常规的室温长高温后退火方式,通过低温长高温退工艺可以缓解应力、削弱界面粗化和避免高温生长对阻挡层和Cu薄膜结构的破坏.最后结合sol-gel法将Pb(Zr0.4Ti0.6)O3(PZT)生长在该含Cu异质结上,制备得SRO/PZT/SRO/Ni-Al/Cu/Ni-Al/SiO2/Si含Cu铁电电容器,研究了电容器的薄膜结构、铁电性能和漏电特性等,发现制备的含Cu铁电电容器具有很好的铁电性能,如电滞回线趋势饱和,剩余极化强度高达~42 C/cm2,矫顽电压为~1.0 V,介电常数~1600,漏电流~1.8310-4 A/cm2,以及良好的抗疲劳特性和保持特性等,表明导电性优良的Cu薄膜可以应用于高密度高性能铁电电容器.对其漏电机理研究表明,SRO/PZT/SRO含Cu铁电电容器满足空间电荷限制传导机理.To integrate ferroelectric capacitor with copper thin film, SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack is fabricated by magnetron sputtering with Ni-Al as the barriers between Cu and SiO2/Si and between Cu and SRO simultaneously in order to segregate Cu from its adjacent oxide layers for avoiding interdiffusions/reactions when samples are annealed at a high temperature. XRD and AFM are employed to study microstructure and surface morphology respectively. The Cu diffraction peaks and the uniform surfaces are found in SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack at a high temperature of 750 ℃, implying that the SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack possesses excellent stability. It is also found that growing at the lower temperature followed by annealing at a high temperature is better than current growing at the room temperature followed by annealing at a high temperature in that the former can relax stresses and reduced the roughness of interfaces to prevent the destruction of barrier and Cu layers at the high temperature. Moreover, PZT is grown on a SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack by the sol-gel method to construct a ferroelectric capacitor with copper, and the microstructure, the ferroelectric performance and leakage are investigated. The good ferroelectric properties of the capacitor with copper are presented, including a saturated hysteresis loop, remnant polarization ~42 C/cm2, coercive voltage ~1.0 V, dielectric constant ~1600, leakage current ~1.8310-4 A/cm2, excellent fatigue resistance, and good retention performance, indicating that high conductivity copper thin film has a promising application to high density and performance ferroelectric memory. Analysis of the leakage fitting also suggests that bulk-limited space-charge-limited conduction (SCLC) acts as the leakage current mechanism in the capacitor.
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Keywords:
- copper/
- PZT/
- ferroelectric capacitor/
- Ni-Al
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