Investigation of a High Quality and Ultraviolet-Light Transparent Plasma-Enhanced Chemical Vapor Deposition Silicon Nitride Film for Non-Volatile Memory Application

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Abstract
A high quality and ultraviolet-light transparent (UV-transparent) plasma enhanced chemical vapor deposition (PECVD) silicon nitride ( SiNx) film is developed to form passivation layer for non-volatile memory devices. Comparing to the conventional PECVD SiNxfilm known to have tensile stress and opacity to ultraviolet-light (UV-light), the proposed SiNxfilm with very low compressive stress ( 70% for 1.6 µ 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/NH3flow 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 SiNxfilm has been successfully applied to erasable programming read-only memory (EPROM's) devices, and very good UV-erasability and reliability performances are demonstrated.