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

Abstract

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.