Application of plasma enhanced chemical vapor deposition silicon oxynitride layers in nonvolatile semiconductor memory devices

In this paper, the authors present the new double gate dielectric structure for the nonvolatile semiconductor memory (NVSM) devices which is based of hafnium dioxide (HfO2). The novelty of this structure relays on the introduction of ultrathin silicon oxynitride (SiOxNy) formed by plasma enhanced chemical vapor deposition (PECVD). Fabricated test structures with the PECVD layers show repetitious behavior of the hysteresis characteristics in comparison to structure with silicon dioxide as the tunnel (bottom) dielectric, which the stability of hysteresis loop is observed after completing first stressing loop. Moreover, the memory window expressed as the flat-band voltage shift versus stress voltage is very wide (1.68 V) and the maximum charge which can be stored by the double gate dielectric stack is of the order of 6 x 10(12) (cm(-2)). Comparison of current density versus gate voltage characteristics of investigated metal-insulator-semiconductor systems demonstrated significantly a decrease of the leakage current for double gate dielectric layers with PECVD oxynitride. In addition, the dielectric constant of SiOxNy (annealed)/HfO2 system is about 11.7 which results in the greatest decrease of equivalent-oxide thickness value among the investigated dielectric stacks. The results presented in this paper show a potential to apply PECVD silicon oxynitride layers in NVSM devices. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3054353]