Electrochemical Studies of W Corrosion for Low Resistive Contact in the 28 nm Technology Node

Tungsten missing was observed at the interface between contact barrier layer and W in the 28 nm node contact process. The potentiodynamic polarization scans showed that H2O2 in the W chemical-mechanical-polishing slurry increased the potential difference between the diborane (B2H6) reduced atomic layer deposited (ALD) W and TiN, suggesting that there is a high tendency for galvanic corrosion to occur. This potential difference kept constant, but the corrosion current density increased when the H2O2 concentration increased. The TEM image showed the depth of ALD W missing is proportional to the H2O2 concentration, which agrees with the electrochemical testing results. ALD W films with various pre- and post-treatments and their correlations with the degree of W missing were also investigated.