研究了基于Ni电极和原子层淀积的ZrO2/SiO2/ZrO2对称叠层介质金属-绝缘体-金属(MIM)电容的电学性能.当叠层介质的厚度固定在14 nm时,随着SiO2层厚度从0增加到2 nm,所得电容密度从13.1 fF/μm2逐渐减小到9.3 fF/μm2,耗散因子从0.025逐渐减小到0.02.比较MIM电容的电流-电压(I-V)曲线,发现在儈压下电流密度随着SiO2厚度的增加而减小,在低压下电流密度的变化不明显,还观察到电容在正、负偏压下表现出完全不同的导电特性,在正偏压下表现出不同的儈、低场I-V特性,而在负偏压下则以单一的I-V特性为主导.进一步对该电容在儈、低场下以及电子顶部和底部注入时的导电机理进行了研究.结果表明,当电子从底部注入时,在儈场和低场下分别表现出普尔-法兰克(PF)发射和陷阱辅助隧穿(TAT)的导电机理;当电子从顶部注入时,在儈、低场下均表现出TAT导电机理.主要原因在于底电极Ni与ZrO2之间存在镍的氧化层(NiOx),且ZrO2介质层中含有深浅两种能级陷阱(分别为0.9和2.3 eV),当电子注入的模式和外电场不同时,不同能级的陷阱对电子的传导产生作用.%The electrical characteristics of Ni electrode-based metal-insulator-metal (MIM) capacitors have been investigated with atomic layer deposited ZrO2/SiO2/ZrO2 symmetric stacked-dielectrics. When the thickness of the stacked-dielectrics is fixed at 14 nm, the resulted capacitance density decreases from 13.1 fF/m2 to 9.3 fF/m2, and the dissipation factor is reduced from 0.025 to 0.02. By comparison of current-voltage (I-V ) curves of different MIM capacitors, it is found that the leakage current density in the high voltage region decreases gradually with the increasing thickness of SiO2, and it does not exhibit clear change in the low voltage region. Meanwhile, the capacitors show different conduction behaviors under positive and negative biases with increasing the thickness of SiO2 from 0 to 2 nm. Under the positive bias, different I-V characteristics are demonstrated at high and low electric fields, respectively. However, a single I-V characteristic is dominant under the negative bias. Further, the conduction mechanisms of the capacitors are investigated under the electron bottom and top injection modes, respectively. It is found that the Poole-Frenkel emission and the trap-assisted tunneling are dominant in the high and low field regions, respectively, for the electron bottom injection; however, the trap-assisted tunneling is dominant in the whole field region for the electron top injection. These are attributed to the formation of a thin NiOx interfacial layer between the Ni bottom-electrode and the ZrO2 dielectric layer, as well as the existence of both deep and shallow level traps (0.9 and 2.3 eV) in the ZrO2 dielectric. Therefore, the level trap plays a key role in the electron conduction in the MIM capacitor under different electron injection modes and different electric fields.
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