Damascene and subtractive processing of narrow tungsten lines: Resistivity and size effect

Narrow W lines with linewidths down to ~40 nm were manufactured by both damascene and subtractive processing. The dependence of the resistivity on the linewidth was studied for different deposition temperatures of the W layer. Generally, the resistivity decreases for decreasing deposition temperature of W. The resistivity increases with decreasing linewidth for both processes due to size effects. However, the W damascene lines show a much steeper increase of the resistivity than etched W lines. In the case of the etched lines the grain size is already fixed after deposition of the W and, therefore, the resistivity increase is caused by an increase of the surface scattering contribution solely. In the case of the damascene lines the line geometry restricts the grain size and, therefore, with decreasing linewidth both an increase of the grain boundary scattering and of the surface scattering contributes to the resistivity. The different behavior of the resistivities can be understood within a compact model ...