CVD TiN using Tic14 and N€b chemistry has been implemented successllly in cylindncally shaped Tal03 storage capacitor as a bamer layer in poly-SiRiN double upper electrode. Electrical characteristics of TaZOs capacitor with CVD TiN double electrode were superior to that with PVD TiN and it was attributed to nearly 100% conformality of CVD TiN. However, it was also found that minimizing chlorine content in CVD TiN f i l m was essential to achieve low leakage current level, and in-situ post annealing of CVD TiN f i l m in N€% ambient was effective in reducing chIorine content.
For tantalum pentoxide capacitors in 1 Gbit dynamic random access memory, titanium nitride is adopted as the top electrode. After postannealing at temperatures higher than 750 °C, the capacitance of Ta2O5 reduces due to an interfacial reaction between TiN and Ta2O5. This was studied by high resolution electron microscopy and energy dispersive spectroscopy with a 1 nm electron probe. It is found that voids form along the interface between TiN and Ta2O5 and a large proportion of Ta dissolves into the TiN film. The origin of the reaction is concluded to be a large solid solubility of Ta in TiN. After Ta outdiffusion into TiN, vacancies agglomerate and form voids in Ta2O5 and thereby reduce its capacitance. Since the driving force of the reaction is the solid solubility of Ta in TiN, the amount of the reaction is affected by the thickness of the TiN films.
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