电离辐射对部分耗尽绝缘体上硅器件低频噪声特性的影响

本文针对辐射前后部分耗尽结构绝缘体上硅(SOI)器件的电学特性与低频噪声特性开展试验研究. 受辐射诱生埋氧化层固定电荷与界面态的影响, 当辐射总剂量达到1 M rad(Si) (1 rad = 10^-2 Gy)条件下, SOI器件背栅阈值电压从44.72 V 减小至12.88 V、表面电子有效迁移率从473.7 cm²/V·s降低至419.8 cm²/V· s、亚阈斜率从2.47 V/dec增加至3.93 V/dec; 基于辐射前后亚阈斜率及阈值电压的变化, 可提取得到辐射诱生界面态与氧化层固定电荷密度分别为5.33×10¹¹ cm^{- 2}与2.36×10¹² cm^-2. 受辐射在埋氧化层-硅界面处诱生边界陷阱、氧化层固定电荷与界面态的影响, 辐射后埋氧化层-硅界面处电子被陷阱俘获/释放的行为加剧, 造成SOI 器件背栅平带电压噪声功率谱密度由7×10^{- 10} V²·Hz^-1增加至1.8×10^-9 V² ·Hz^-1; 基于载流子数随机涨落模型可提取得到辐射前后SOI器件埋氧化层界面附近缺陷态密度之和约为1.42×10¹⁷ cm^-3·eV^-1和3.66×10¹⁷ cm^-3·eV^-1. 考虑隧穿削弱因子、隧穿距离与时间常数之间关系, 本文计算得到辐射前后埋氧化层内陷阱电荷密度随空间分布的变化.

Radiation effects on the low frequency noise in partially depleted silicon on insulator transistors

The transfer characteristics and low-frequency noise behavior of partially depleted silicon on insulator n-channel metal-oxide-semiconductor transistors after γ-ray irradiation up to a total dose of 1M rad (Si) have been investigated in this paper. Due to the radiation-induced positive buried-oxide trapped charges and the interface traps, the back gate threshold voltage decreases from 44.72 to 12.88 V, and the electron field effect on mobility decreases from 473.7 to 419.8 cm²/V·s; while the sub-threshold swing increases from 2.47 to 3.93 V/dec. Based on the measurements of sub-threshold swing and the back gate threshold voltage, the variations of extracted radiation-induced buried oxide trapped charge and interface trap densities, are about 2.36×10¹² cm^-2 and 5.33×10¹¹ cm^-2 respectively. In addition, the normalized back gate flat-band voltage noise power spectral density is a sensitive function of radiation-induced buried oxide trapped charges and interface traps, which increases from 7×10^-10 V²·Hz^-1 to 1.8×10^{- 9} V²·Hz^-1. According to the carrier number fluctuation model, the extracted trap density near the interface between channel and buried oxide increases from 1.42×10¹⁷ to 3.66×10¹⁷ cm^{- 3}·eV^-1. By considering the tunneling attenuation coefficient of the electron wave function and the tunneling depth of the electron in the buried oxide, the spatial distribution of trapped charges in the buried oxide before and after radiation are calculated and discussed.