Analysis of ${\rm P}_{b}$ Centers in Ultrathin Hafnium Silicate Gate Stacks

A "kink" in the capacitance-voltage (C-V) characteristics of MOS capacitors with an ultrathin interfacial layer of 7-8 ¿ in a hafnium silicate gate dielectric is analyzed via high-low frequency C-V and quantum-mechanical calculations. Hole and electron traps (amphoteric) with energy levels determined at Ev+0.44 eV and Ev+0.89 eV are surmised to be P_b1 and P_b0 centers, respectively. Of these two defects, those in the lower half of the bandgap cause an asymmetric kink in the C-V characteristics that can further be attributed to an additional level at Ev+0.32 eV, corresponding to centers. With reducing temperatures, the peaks move toward the band edge with increasing magnitude, consistent with multiphonon emission models of capture behavior.