Barrier properties for oxygen diffusion in a TaSiN layer

Annealing in O-2 at temperatures above 650 degrees C is required fcr a thin ferroelectric capacitor. Reduction of the leakage current and an increase of capacitance can be attained in the charge storage capacitor through this annealing. A stacked structure capacitor cell must be practically employed in metal oxide semiconductor large scale integrated circuits (MOSLSI). In this capacitor cell with a conventional Pt/TiN/poly-Si lower electrode, however, O-2 annealing can not be attained at high temperature because peeling of the TiN barrier layer and the formation of a thin oxide layer at the surface of poly-Si occur. An noncrystalline TaSiN layer has been studied with respect to the barrier effect for oxygen diffusion used in the barrier layer of the lower electrode, The penetration depth of oxygen diffusion decreases markedly with increasing Si composition in a TaSiN layer and reaches 20 nm deep in a Ta.22Si.35N.43 layer. However, the resistivity increases with this increase. A good diffusion barrier layer with low sheet resistance is attained in a Ta.50Si.16N.34 layer. Penetration depth below 40 nm is obtained in a slightly Si-rich Ta.36Si.27N.37 laser for O-2 annealing at 850 degrees C.