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.