Composition dependence of the work function of $Ta1−xAlxNy$ metal gates

It is shown that the work function of $Ta1−xAlxNy$ depends on the electrode and gate dielectric compositions. Specifically, the work function of $Ta1−xAlxNy$ increased with $SiO2$ content in the gate dielectric, reaching as high as $5.0eV$ on $SiO2$⁠; the work function was nearly $400mV$ smaller on $HfO2$⁠. In addition, the work function decreased with increasing nitrogen content in the $Ta1−xAlxNy$ metal gate. Increasing Al concentration increased the work function up to about 15% Al, but the work function decreased for higher Al concentrations. Chemical analysis shows that Al–O bonding at the interface correlates with the observed work function values.