SIMS and XPS Analysis of Interfaces in Passivation Layers on C-Silicon Under Low-Energy Electron Radiation

In order to investigate chemical structure change in surface passivation layers of C-silicon material under radiation of low-energy electrons, three kinds of surface passivation C-silicon material are prepared, which are mono-SiO2 layer, SiO₂/Si₃N₄ compound layers and boronsilicate glass/Si₃N₄ compound layers. They are radiated under electrons of E_max=70 keV from electron accelerator for 6 hours in air atmosphere. Depth changes of Si, N, B before and after electron radiation are measured by secondary ion mass spectroscopy(SIMS) and argon ion etching X-ray photoelectron spectroscopy(XPS). The results show that changes at interfaces of SiO₂/Si are remarkable both in mono-SiO₂ passivation samples and Si₃N₄/SiO2 passivation samples. The possible reason is stoichiometric proportion of SiO₂ at the interface is changed to SiO_x（x<2） under irradiation because of Si-O bond breaking. In case of Si₃N₄/SiO₂/Si passivation sample, the dissociated oxygen results from Si-O bond breaking might drift through SiO₂ to SiO₂/Si₃N₄ interface. In case of Si₃N₄/boronsilicate glass/Si sample, chemical structure changes in interfaces of boronsilicate glass/Si₃N₄ and boronsilicate glass/Si are less remarkable than those both of SiO₂/Si and Si₃N₄/SiO₂/Si samples. It indicates that the radiation damage of surface passivation layers of C-silicon material from low-energy electrons mainly takes place at interface of SiO₂/Si, which can not be noticeably improved by SiO₂/Si₃N₄ combined passivation. While using boronsilicate glass/Si₃N₄ combined passivation can help to keep chemical structure stable at interfaces between surface passivation layers of C-silicon material under radiation of low-energy electrons in air atmosphere.