叠层SOI MOSFET不同背栅偏压下的热载流子效应

Hot Carrier Effect of Double SOI MOSFET Under Different Back-Gate Bias Voltages

叠层绝缘体上硅(SOI)器件通过调节背栅偏压来补偿辐照导致的阈值电压退化,对于长期工作在辐射环境中的叠层SOI器件,热载流子效应也是影响其可靠性的重要因素。因此,采用加速老化的方法研究了叠层SOI NMOSFET在不同背栅偏压下的热载流子效应。实验结果表明,在负背栅偏压下有更大的碰撞电离,而电应力后阈值电压的退化却随着背栅偏压的减小而减小。通过二维TCAD仿真进一步分析了不同背栅偏压下的热载流子退化机制,仿真结果表明,背栅偏压在改变碰撞电离率的同时也改变了热电子的注入位置,正背栅偏压下会有更多的热电子注入到离前栅中心近的区域,而在负背栅偏压下则是注入到离前栅中心远的区域,从而导致正背栅偏压下的阈值电压退化更严重。

Double silicon-on-insulator(SOI)devices compensate for radiation-induced threshold voltage degradation by adjusting back-gate bias voltage.For double SOI devices operating in radiation environments for long periods of time,hot carrier effect is also an important factor affecting the reliability.Therefore,hot carrier effect of double SOI NMOSFET under different back-gate bias voltages was investigated by using the accelerated aging method.The experimental results indicate that there is greater impact ionization under negative back-gate bias voltage.In contrast,the degradation of threshold voltage after electrical stress decreases as the back-gate bias voltage decreases.The mechanism of hot carrier degradation under different back-gate bias voltages was further analyzed by 2D TCAD simulation.The simulation results show that back-gate bias voltage changes the impact ionization rate and the injection position of hot electrons.More hot electrons are injected into the region close to the center of front gate under positive backgate bias voltage,while under ne-gative back-gate bias voltage they are injected far from the center of front gate,leading to more severe degradation of threshold voltage under positive back-gate bias voltage.