双极型晶体管总剂量效应的统计特性

Statistical characteristics of total ionizing dose effects of bipolar transistors

双极型晶体管的总电离剂量辐照效应主要体现在基极电流(IB)的退化,其作用机理是电离辐射在SiO_(2)中及Si/SiO_(2)界面作用导致的氧化物陷阱电荷面密度(Not)和界面陷阱电荷面密度(Nit)的增长.本文基于定制设计的栅控横向PNP晶体管,开展了大样本、多剂量点的电离总剂量效应实验,获得了双极型晶体管I_(B),N_(ot),N_(it)的分散性及其随总剂量变化的统计特性,初步建立了晶体管损伤分散性与Not分散性的关联.该研究成果可以有效支撑双极型电路辐射可靠性的机理研究与定量评估.

The base current(IB)of silicon bipolar transistor degrades when it is subjected to total ionizing dose(TID)irradiation,which is due to the generation of oxide trapped charges(Not)in the oxide layer and interface traps(Nit)at the silica/silicon interface.In this work,we investigate the statistical characteristic of IB of bipolar transistors and its possible microscopic origin.Especially,we carry out TID irradiation experiments on a large sample size of gated lateral PNP(GLPNP)transistors.Forty GLPNP transistors are sequentially irradiated to the total doses of 0.6 krad(Si),2.6 krad(Si),4.0 krad(Si),7.4 krad(Si),and 10.8 krad(Si).The statistical characteristics of their I_(B),N_(ot),and N_(it) are obtained from the Gummel,gate sweep(GS),and sub-threshold sweep(DS)curves,respectively.It is found that no matter what the dose is,IB,Not,and Nit all follow a lognormal distribution.However,the distribution parameters change as the irradiation dose increases.Remarkably,the statistical median and standard deviation of IB as a function of dose show a strong correlation with those of Not,but essentially differ from those of Nit.This fact uncovers that for our research objects and dose rate,the sample-to-sample variability of IB mainly stems from the variation of Not.These interesting results should have potential applications in exploring the mechanism and evaluating the irradiation reliability of bipolar microcircuits.