纳米级静态随机存取存储器的α粒子软错误机理研究

Mechanisms of alpha particle induced soft errors in nanoscale static random access memories

本文使用镅-241作为α粒子放射源,开展65和90 nm静态随机存取存储器软错误机理研究,结合反向分析、TRIM和CREME-MC蒙特卡罗仿真揭示α粒子在器件中的能量输运过程、沉积能量谱和截面特性.结果表明, 65 nm器件的软错误敏感性远高于90 nm器件,未发现翻转极性.根据西藏羊八井地区4300 m海拔的实时测量软错误率、热中子敏感性和α粒子软错误率,演算得到65 nm静态随机存取存储器在北京海平面应用的总体软错误率为429 FIT/Mb,其中α粒子的贡献占比为70.63%.基于反向分析结果构建器件三维仿真模型,研究α粒子入射角度对单粒子翻转特性的影响,发现随着入射角度从0°增大至60°,灵敏区中粒子数峰值处对应的沉积能量值减小了40%,原因为衰变α粒子的能量较低,入射角度增大导致α粒子穿过空气层和多层金属布线的厚度增大1/cos(q)倍,引起粒子能量减小,有效LET值随之减小.随着入射角度从0°增大至60°,单粒子翻转截面增大了79%,原因为65 nm器件灵敏区中明显的单粒子翻转边缘效应.

In this paper,the Am-241 is used as an alpha particle radioactive source to investigate the soft error mechanism in 65-nm and 90-nm static random accessmemory(SRAM).Combining reverse analysis,TRIM and CREME-MC Monte Carlo simulation,the energy transport process,deposited energy spectrum and crosssection characteristics of alpha particles in the device are revealed.The results show that the soft error sensitivity of the 65-nm device is much higher than that of the 90-nm device,and no flipping polarity is found.According to the real-time measured soft error rate at an altitude of 4300 m in Tibetan Yangbajing area,the thermal neutron sensitivity and alpha particle soft error rate,the overall soft error rate of 65-nm SRAM used at sea level of Beijing city is 429 FIT/Mb,and the contribution from alpha particles is 70.63%.Based on the results of reverse analysis,a three-dimensional simulation model of the device is constructed to study the influence of the incident angle of alpha particles on the single event upset characteristics.It is found that the corresponding deposition energy value at the peak of the number of particles in the sensitive region decreases by 40%with the incident angle increasing from 0°to 60°.While the single event upset cross sectionincreases by 79%due to the apparent single event upset edge effect in a sensitive region of the 65-nm device.