极低剂量率下BJT基区隔离氧化层电离辐射感生缺陷的演化机制

The Enhanced low dose rate sensitivity (ELDRS) effect of bipolar devices is an internationally recognized problem in the study of the ionization total dose effects of bipolar devices. Especially, recent research shows the enhancement factor (EF) of some bipolar devices does not exhibit the expected saturation phenomenon at ultra-low dose rate environments (<10mrad (Si) /s). In order to obtain the physical mechanism that causes this phenomenon, this project will focus on the sensitive area to ELDRS effect of bipolar transistor, which is the base isolation oxide layer and SiO2/Si interface. Using the gated lateral PNP transistors and a special test structure, various defects and reactions associated with ELDRS in the isolated oxide layer of the base region will be studied by computer analysis of reaction kinetics equation. The evolution behavior of key defects in different time scales at a certain dose rate (in the range of 1mrad(Si)/s to 0.1rad(Si)/s) will be obtained by controlling the key defect concentration and reaction process during analyzing the reaction kinetics equation. The purpose of this project study is to obtain the generation and annealing mechanism of interface trap charge within the dose rate range (1mrad(Si)/s~0.1rad(Si)/s), and then identify the key defect types and the reaction that lead to the enhancement factor unsaturation in very low dose rate environments.

双极器件的低剂量率损伤增强（ELDRS）效应是目前国际公认的双极器件电离总剂量效应研究的难点问题，特别是近几年研究发现极低剂量率环境下（＜10mrad(Si)/s）部分双极器件的增强因子(Enhancement Factor，EF)并未出现预期的饱和现象，为了获得产生这一现象的物理机制，本项目以双极器件基本单元双极晶体管为研究对象，着眼于ELDRS效应产生的敏感区域即基区隔离氧化层及SiO2/Si界面处，借助栅控横向PNP晶体管及特制的测试结构，通过计算机对基区隔离氧化层内各类与ELDRS效应产生相关的缺陷反应动力学方程的解析，控制其中的关键缺陷浓度及反应过程，研究一定剂量率范围内（1mrad(Si)/s~0.1rad(Si)/s）不同时间尺度内关键缺陷的演化行为，获得该剂量率范围内界面陷阱电荷的产生及退火机制，确定导致极低剂量率环境下增强因子不饱和的关键缺陷类型及反应过程。

为了获得极低剂量率环境下(＜10mrad(Si)/s)部分双极器件的增强因子(Enhancement Factor，EF)未出现预期的饱和现象的物理机制，本项目以GLPNP及GNPN晶体管作为研究对象，开展了不同剂量率(1mrad(Si )/s~0.1rad(Si)/s)的辐照试验研究：获得了敏感区域即基区隔离氧化层及SiO2/Si界面处，氧化物陷阱电荷和界面态随剂量率及累积剂量的变化情况；并通过对基区隔离氧化层内各类与ELDRS效应相关的缺陷反应动力学方程的计算解析，研究了不同时间尺度内关键缺陷的演化行为，获得了该剂量率范围内界面陷阱电荷的产生及退火机制；最终，结合不同温度辐照、注H辐照及不同栅偏辐照试验，验证了上述双极器件极低剂量率下的EF不饱和的物理机制及缺陷演化行为，认为：低剂量率条件下，单位时间内入射射线在隔离氧化层中电离产生的电子空穴对数量较少，减少了电子空穴对的复合概率，增强了空穴与氧化层中氢化缺陷反应释放H+的过程，H+到达Si/SiO2界面处，与Si-H键发生去钝化反应产生界面陷阱电荷；相同总剂量水平下，低剂量率辐照条件下产生更多的界面态密度及H2，界面处逐渐堆积的H2抑制了去钝化反应，阻碍界面态的生长，导致低剂量率下双极器件达到辐射损伤饱和的总剂量，小于相对高的剂量率下达到辐射损伤饱和的总剂量。