部分耗尽结构绝缘体上硅器件的低频噪声特性

Low frequency noise behaviors in the partially depleted silicon-on-insulator device

针对部分耗尽结构绝缘体上硅(silicon-on-insulator,SOI)器件低频噪声特性展开实验与理论研究.实验结果表明,器件低频噪声主要来源于Si O2-Si界面附近缺陷态对载流子的俘获与释放过程;基于此理论可提取前栅和背栅氧化层界面附近缺陷态密度分别为8×1017eV-1·cm-3和2.76×1017eV-1·cm-3.基于电荷隧穿机理,在考虑隧穿削弱因子、隧穿距离与时间常数之间关系的基础上,提取了前、背栅氧化层内缺陷态密度随空间的分布情况.此外,SOI器件沟道电流归一化噪声功率谱密度随沟道长度的增加而线性减小,这表明器件低频噪声主要来源于沟道的闪烁噪声.最后,基于电荷耦合效应,分析了背栅电压对前栅阈值电压、沟道电流以及沟道电流噪声功率谱密度的影响.

Low frequency noise in the partially depleted silicon-on-insulator （SOI） NMOS device is investigated in this paper. The experimental results show low frequency noise behaviors are in good consistence with classical noise model. Based on McWhorter model, the low frequency noise in the SOI device results from the exchange of carriers between channel and oxide. The densities of trapped charges in the front gate oxide and buried oxide are extracted. Due to the difference between manufacture processes, the extracted density of trapped charges in the buried oxide （Art = 8 × 10^17 eV-1·cm-3） is larger than that in the gate oxide （Nt = 2.767 × 10^17 eV-1·cm-3）, and the result is in good agreement with testing result of transfer characteristics in part 2. Based on the charge tunneling mechanism, the spatial distribution of trapped charges in the gate oxide and buried oxide are extracted by using the tunneling attenuation coefficient （A = 0.1 nm for SiO2） and time constant （τ0 = 10^-10 S）, and the result also proves that the trap in buried oxide is larger than that in gate oxide. In addition, the influence of channel length on the low frequency noise in the SOI device is discussed. The variations of normalized channel current noise power spectral density with channel length are investigated at four frequencies（10 Hz, 25 Hz, 50 Hz, and 100 Hz）. The experimental results show that the normalized noise power spectral density decreases linearly with the increase of channel length, which indicates the low frequency noise of SOI device is mainly caused by the flicker noise in the channel, and the contribution of source/drain contact and parasitic resistances could be ignored. Finally, the dependences of back gate voltage on the front gate threshold voltage, front channel current and front channel noise are discussed by considering the charge coupling effect. The experimental results show the measured channel current and channel noise with applying front gate voltage and back gate voltage simultaneously are larger than those with applying the front gate voltage and back gate voltage separately.