Small area versus narrow line width effects on the C49 to C54 transformation of TiSi2

Polycrystalline silicon (poly) structures of equal area and varying line width were subjected to a standard self-aligned TiS₂ process. The poly lines had widths of 0.4, 0.5, 1.0, and 2.0 μm and the total contiguous silicided area ranged from 7 to over 2500 μm₂. On all large area structures (silicided area >100 μm₂) our findings were consistent with the well-known narrow line width effect; i.e., the kinetics of transformation were adversely affected as the line width decreased, but with a sufficiently high thermal budget complete transformation to the C54 phase was possible. However, on structures with silicided area less than 100 μm ₂, a small area effect was observed in addition to the narrow line width effect. A percentage of small area lines remained entirely in the C49 phase (because of an apparent absence of C₅₄ nucleation sites) regardless of the thermal budget. This percentage increased with decreasing silicided area but was independent of the line width. Only the small area lines that did transform to the C54 phase exhibited the narrow line width effect. Therefore, for the range of line widths studied, the narrow line width mechanism and the small area mechanism were distinct