1.Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu 610200, China 2.College of Physics and Electronic Information Engineering, Neijiang Normal University, Neijiang 641112, China 3.School of Electronic Science and Engineering, University of Electronic science and Technology of China, Chengdu 610000, China 4.Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621000, China
Fund Project:Project supported by the Scientific Challenge Project, China (Grant No. TZ2016003-1)
Received Date:03 November 2020
Accepted Date:08 February 2021
Available Online:25 June 2021
Published Online:05 July 2021
Abstract: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 IB, Not, and Nit 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. Keywords:bipolar transistor/ total ionization dose effect/ statistical characteristics/ correlation
实验获得的不同总剂量条件下40只GLPNP样本的基极电流的统计分布见图2. 可以看到, 基极电流的分布是不对称的. 当总剂量较小时, 较多的样本分布在中值的右侧; 总剂量较大时, 较多的样本分布在中值的左侧. 对于4.0 krad(Si)的总剂量, 分布基本对称. 研究发现这些分布均满足对数正态分布(lognormal distribution)[20], 其概率密度函数(probability distribution function)为 图 2 不同总剂量条件下GLPNP基极电流的分布特性 Figure2. Statistical characteristics of the base current of GLPNP under different total doses as indicated in each subfigure.