INVESTIGATION OF A HIGH-QUALITY AND ULTRAVIOLET-LIGHT TRANSPARENT PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION SILICON-NITRIDE FILM FOR NONVOLATILE MEMORY APPLICATION

A high quality and ultraviolet-light transparent (UV-transparent) plasma enhanced chemical vapor deposition (PECVD) silicon nitride (SiNz) film is developed to form passivation layer for non-volatile memory devices. Comparing to the conventional PECVD SiNx film known to have tensile stress and opacity to ultraviolet-light (UV-light), the proposed SiNz film with very low compressive stress (<1x10(9) dyn/cm(2)) and excellent UV-transmittance (>70% for 1.6 mu m-thick film) can be achieved. The film stress is strongly related to RF input power during deposition process. The UV-transmittance is influenced by pressure and SiH4/NH3 flow ratio. It is also shown that the UV-transmittance is closely correlated to refractive index (RI), film density as well as N/Si ratio inside the film. This SiNx film has been successfully applied to erasable programming read-only memory (EPROM's) devices, and very good UV-erasability and reliability performances are demonstrated.