Formation and nonvolatile memory characteristics of W nanocrystals by in-situ steam generation oxidation

The authors provide the formation and memory effects of W nanocrystals nonvolatile memory in this study. The charge trapping layer of stacked a-Si and WSi2 was deposited by low pressure chemical vapor deposition (LPCVD) and was oxidized by in-situ steam generation system to form uniform W nanocrystals embedded in SiO2. Transmission electron microscopy analyses revealed the microstructure in the thin film and X-ray photon-emission spectra indicated the variation of chemical composition under different oxidizing conditions. Electrical measurement analyses showed the different charge storage effects because the different oxidizing conditions influence composition of trapping layer and surrounding oxide quality. Moreover, the data retention and endurance characteristics of the formed W nanocrystal memory devices were compared and studied. The results show that the reliability of the structure with 2% hydrogen and 98% oxygen at 950 °C oxidizing condition has the best performance among the samples.