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A silicon nitride film is one of the most important factors for determining the trapping efficiency of nonvolatile silicon-oxidenitride-oxide-silicon (SONOS) memory devices. In this work, we focus on the nitride-layer deposition at different temperatures by low-pressure chemical vapor deposition (LPCVD) and examine the trap levels through photoluminescence (PL) measurement. Moreover, using DC current-voltage (I-V) and capacitance-voltage (C-V) measurements, we investigate the electrical characteristics, breakdown characteristics, and the relationship between performance and trap-level depth. Our results show that the silicon nitride deposited by LPCVD at 830 C has better performance and reliability. However, the charge-to-breakdown (Q BD ) quality of the nitride film deposited at 600 C is better due to the suppression of the influence of the transition layer near the interface at the lower deposition temperature. In summary, this study can help researchers to understand the temperature effect on nitride-film deposition and the analysis of its electrical characteristics.

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A significant reliability improvement in silicon–oxide–nitride–oxide–silicon (SONOS) flash memory devices by band-gap engineering of the nitride layer has been attained. The gradually varied reaction gas flow rate during deposition has generated special nitride films with non uniform composition profiles and band gaps. As a result, SONOS devices with partially Si-rich nitride structures have exhibited superior cycling endurance, radiation hardness, and data retention compared with devices with a uniform standard nitride. The marked improvement can be attributed to the increased charge-trapping/detrapping efficiency of the nitride layer since a significant number of highly accessible trapping levels have been created in the nitride that has a graded band gap. In addition, the deepened barrier heights between the nitride and its surrounding oxides may also reduce undesirable charge-loss probability and assist in charge storage. Because the dimension of flash memory cells is continuously shrinking, the proposed technique will be valuable for mass storage applications.