Effect of deposition chemistry and annealing on charge in HfO₂ stacks

Charge in HfO₂ gate stacks grown from various metal-organic chemical vapor deposition sources has been studied using nMOS capacitors with a damage-free Cr gate process. It is found that the charge in the stack is mainly concentrated at the interfaces between materials. The effect of postdeposition anneal depends on the high-κ/ film-deposition chemistry. A forming gas anneal can reduce interface charge, hysteresis, and interface state densities for HfO₂ films grown from various sources. The marked difference in the annealing response of similar films deposited from different precursors, however, strongly suggests that charge in these stacks is related to the deposition chemistry and may be due to residual impurities or defects left in the film from the deposition.