沟槽型MOSFET放大器γ射线辐照效应研究

Gamma ray irradiation response of the trench MOSFET amplifier

研发高抗辐照性能的金属氧化物半导体场效应晶体管(Metal Oxide Semiconductor Field Effect Transistor,MOSFET)放大器等电子器件对于核环境作业机器人至关重要。用^(60)Co-γ射线对三个商用沟槽型MOSFET放大器进行了原位辐照测试,研究了辐照前后的电学性能变化。结果表明:三个MOSFET放大器分别在累计辐照总剂量达到982.6 Gy、986.2 Gy和1082.4 Gy后失效。将光学显微镜观察、热发射显微技术失效定位、聚焦离子束技术解剖制样、扫描电镜和透射电镜的微观结构和微区成分表征等方法结合起来,对MOSFET放大器的芯片进行了失效分析,揭示了当MOSFET放大器在带电工作状态下受到γ射线辐照时,栅极氧化物捕获电荷的聚集会导致阈值电压和击穿电压降低,高剂量^(60)Co-γ射线辐照引入的电子-空穴对在电场作用下,大量积聚所引起的局部区域高电场和高热的叠加作用,使源极铝金属局部发生熔融并产生烧蚀缺陷区,最终引起栅极与源极之间短路而导致其失效的机理。

[Background]Developing electronic devices,such as metal oxide semiconductor field effect transistor(MOSFET)amplifiers with high radiation resistance,is crucial for robots working in nuclear environments.[Purpose]This study aims to test the irradiation resistance performance of commercial MOSFET amplifiers and reveal the corresponding irradiation failure mechanism.[Methods]An in-situ gamma rays irradiation experiment platform was employed to conduct irradiation test on three trench MOSFET amplifiers using a^(60)Co source.Response to different doses,and the electrical properties of these MOSFET amplifiers were investigated before and after irradiation.The failure analysis methods including electrical characteristics tests,thermal emission microscopy(EMMI)for failure location determination,focused ion beam(FIB)sample preparation,scanning electron microscope(SEM),and transmission electron microscope(TEM)characterization were employed to reveal the irradiation failure mechanism.[Results]Experimental results showed that the three MOSFET amplifiers failed after irradiation by absorbed doses of 982.6 Gy,986.2 Gy,and 1082.4 Gy,respectively.The drain-source breakdown voltage BVDSS of the MOSFET decreases from 110.5 V to 0.96 V,while the gate-source drive current IGSS increases from 2.9 nA to 81.3 mA,as well as the threshold voltage VGS(th)is not be detected due to the short circuit.[Conclusions]When the MOSFET amplifiers are irradiated in a charged operating state,the accumulation of captured charges in the gate oxide will lead to a decrease in the threshold voltage and breakdown voltage.Electron-hole pairs generated by high-energy and highdose gamma-ray irradiation may continue to accumulate under the action of the circuit electric field,resulting in local high electric fields and high heat areas.The superposition of these high electric fields and high heat areas will cause the source aluminum metal to melt and ablate,causing a short circuit between the gate and the source.