阱接触对28 nm SRAM单粒子多位翻转的影响

Influences of well contact on multiple-cell upsets in 28 nm SRAM

为研究纳米尺度下,特征尺寸减小和阱接触布放方式对单粒子效应电荷收集机制的影响,在北京HI-13串列加速器上开展了国产28 nm静态随机存储器(SRAM)重离子单粒子效应辐照实验研究,获得了不同线性能量转移(LET)值重离子垂直入射下的器件重离子单粒子位翻转截面、多位翻转百分比和多位翻转拓扑图形,并与65 nm SRAM实验数据进行比对,分析了28 nm SRAM重离子单粒子多位翻转物理机理.结果表明,在特征尺寸减小、工作电压降低等因素影响下,器件重离子单粒子翻转阈值减小,位翻转饱和截面明显降低,多位翻转占比增大,拓扑图形可达n行×3列,且呈现间断性的特点,结合28 nm SRAM的全局阱接触布放对电荷收集机制的影响,分析这种现象的产生源于N阱内p型金属-氧化物-半导体间电荷共享所导致的单粒子翻转再恢复.

In order to study the effects of the feature size reduction and well contact placement on the characterization of topology patterns and the charge collection mechanism of device heavy ion single event multiple upset on a nanometer scale,the heavy ion single event effect experiment on the domestic 28 nm static random-access memory(SRAM)is carried out on the experimental platform of HI-13 heavy ion accelerator in Beijing.Based on the mapping relationship between the logical address and physical address of the device,the experimental data are processed,and the 28 nm SRAM heavy ion single event upset cross section curves,multiple upset percentage,and multiple upset topology patterns are obtained.The results are compared with those of heavy ion single event effect experiments in 65 nm SRAM,showing that under the influences of factors such as feature size reduction and lower operating voltage,the heavy ion single event upset threshold and the bit upset saturation cross section of 28 nm SRAM decrease significantly.In the direction perpendicular to the well,owing to the reduced 28 nm SRAM feature size,even if the single nucleon energy of the incident high LET(linear energy transfer)heavy ion is low,its deposited charge is sufficient to affect the three SRAM cells across the well direction due to the combined effect of ion track coverage,well potential modulation caused by the parasitic bipolar amplification effect and carrier diffusion,resulting in the fact that the 28 nm SRAM topology pattern has a shape of n rows×3 columns,which poses new challenges and requirements for the anti-radiation hardened technology with scrubbing and EDAC(error detection and correction).Owing to the global well contact deployment,the charge deposited by the incident ions in the well far away from the well contact is difficult to discharge quickly,and the parasitic bipolar amplification effect lasts longer.The charge sharing competition between two p-channel metal oxide semiconductor in SRAM cell causes the single event upset recovery,which is the fundamental reason why the discontinuity of multiple upset topology pattern appears in28 nm SRAM.This study provides a new anti-radiation hardened idea for suppressing the single event upset by using the parasitic bipolar amplification in the future.