硅基N沟道VDMOS不同偏置下总剂量效应研究

Study on the Total Dose Effect of Silicon-based N-channel VDMOS with Different Bias

通过^(60)Coγ射线辐照试验,研究了不同栅极和漏极偏置下硅基N沟道VDMOS器件的总剂量效应,获得了器件的电学特性与低频噪声特性随辐射总剂量的变化规律。试验结果表明:受辐射诱生的氧化物陷阱电荷与界面陷阱电荷的影响,在栅极偏置为+20 V时,器件的电学特性随累积剂量的增大而退化明显。通过退火试验发现,相比于导通电阻和正向压降,阈值电压、漏电流、亚阈值摆幅和输出电容对于总剂量辐射更加敏感。而在低频噪声特性方面,辐照后器件的沟道电流归一化噪声功率谱密度与正栅极偏置呈现正相关性,与负栅极偏置呈现负相关性。在不同漏极偏置条件下,辐照后器件的沟道电流归一化噪声功率谱密度降低,且基本重合。依据噪声模型,认为N沟道VDMOS内部局域电场分布对辐射感生陷阱电荷的形成影响显著,导致器件Si/SiO_(2)界面或者附近的载流子与陷阱交换引起的沟道电流波动不同,成为低频噪声主要来源。研究结果可为N沟道VDMOS器件的辐射效应评估、筛选和抗辐射加固设计提供参考。

In this paper,the total dose effect of silicon-based N channel VDMOS devices with different gate and drain biases was studied by^(60)Coγ-ray irradiation test.The changes of electrical characteristics and low-frequency noise characteristics of the devices with the total radiation dose were obtained.The experimental results show that when the gate bias is+20 V,the electrical characteristics of the devices deteriorate most obviously with the increase of the cumulative dose.Through annealing test,it is found that threshold voltage,leakage current,subthreshold swing and output capacitance are more sensitive to the total dose radiation than on-resistance and forward voltage drop.In terms of low-frequency noise characteristics,the normalized noise power spectral density of channel current of the irradiated devices shows the positive correlation with positive gate bias and the negative correlation with negative gate bias.Under different drain bias conditions,the normalized noise power spectral density of the channel current of the devices decreases and basically coincides with each other.According to the noise model,the local electric field distribution inside N channel VDMOS has a significant influence on the formation of radiation-induced trap charge,resulting in different channel current fluctuations caused by the exchange between the carriers and the traps at or near the Si/SiO_(2)interface of the device,which becomes the main source of low-frequency noise.The results can provide a reference for the radiation effect evaluation,screening and radiation hardening design of N channel VDMOS devices.