质子与金属布线层核反应对微纳级静态随机存储器单粒子效应的影响分析

金属布线层对微纳级静态随机存储器(static random access memory, SRAM) 质子单粒子效应敏感性的影响值得关注. 利用Geant4针对不同能量(30 MeV, 100 MeV, 200 MeV和500 MeV)的质子与微纳级SRAM器件的核反应过程开展计算, 研究了核反应次级粒子的种类、线性能量传输值(linear energy transfer, LET)及射程情况, 尤其对高LET 值的核反应次级粒子及其射程开展了详细分析. 研究表明, 金属布线层的存在和质子能量的增大为原子序数大于或等于30的重核次级粒子的产生创造了条件, 器件体硅区中原子序数大于60的重核离子来源于质子与钨材料的核反应, 核反应过程中的特殊作用机理会生成原子序数在30至50之间的次级粒子, 且质子能量的增大有助于这种作用机理的发生, 原子序数在30至50之间的次级粒子在器件体硅区的LET值最大约为37 MeV·cm²/mg, 相应射程可达到几微米, 对于阱深在微米量级的微纳级SRAM器件而言, 有引发单粒子闩锁的可能. 研究结果为空间辐射环境中宇航器件的质子单粒子效应研究提供理论支撑.

Effects of nuclear reactions between protons and metal interconnect overlayers on single event effects of micro/nano scaled static random access memory

Since metal interconnect overlayers are central components of micro/nano scaled static random access memory (SRAM), the effects of their presence on proton-induced single-event susceptibility are noteworthy. Geant4 is used to calculate the kinds and probabilities of secondary particles existing in bulk silicon, which are produced from nuclear reactions between protons of different energies (30, 100, 200 and 500 MeV) and micro/nano scaled SRAM. The probabilities of secondary particles with Z≥30 in different overlays are compared with one another; the particles are chiefly coming from nuclear reactions between 500 MeV protons and the SRAM topped with interconnect overlayers. In addition, the kinds and ranges of the secondary particles with high LETs (linear energy transfers) are also analyzed. Results show that there is an increase in the production of secondary particles with Z≥30 due to the presence of metal interconnect overlayers and the rise of proton energy. The secondary particles with Z>60 in bulk silicon are generated by proton interactions with tungsten. As another consequence of the interactions, the secondary particles with 30≤Z≤50 are produced, the probability of which is higher as the proton energy increases. The maximum LET for the secondary particles with 30≤Z≤50 is about 37 MeV·cm²/mg and the corresponding range is several microns, which may induce single event latch-up in micro/nano scaled SRAM with well depths on the order of microns. Results obtained support the theoretic analysis of proton-induced single event effects of aerospace devices in space radiation environment.