Effect of high temperature annealing on the charge trapping characteristics of silicon nanocrystals embedded within SiO2

Metal oxide semiconductor structures with silicon nanocrystals (Si-nc), embedded within SiO 2 were investigated. These structures were fabricated by low temperature chemical vapour deposition of silicon on a thin tunnel oxide (3 nm thick) followed by oxidation and annealing steps. The high temperature annealing is critical since it determines the structural and consequently the charging properties of the samples. Two annealing temperatures were used, 900 and 1100 °C. Samples annealed at 900 °C showed strong charging phenomena due to electron and hole trapping. The density of these trapping sites was estimated to be around 2 × 10 12 cm −2 . Hydrogen annealing showed that the majority of these trapping sites was due to unsaturated bonds, located in the Si-nc plane, probably at the interface of Si-nc with SiO 2 . In contrast, samples annealed at 1100 °C showed a symmetrical ‘memory window’ of 0.6 V due to electron and hole trapping, which was not significantly affected by hydrogen annealing. The density of the trapping sites was in this case estimated to be 2.5 × 10 11 cm −2 .