Study of the Reliability Impact of Chlorine Precursor Residues in Thin Atomic-Layer-Deposited $\hbox{HfO}_{2}$ Layers

Atomic layer deposition (ALD) with HfCl
₄
as a precursor is widely used for HfO
₂
fabrication. Due to the nature of the precursor under study, i.e., HfCl
₄
and H
₂
O, the presence of chlorine residues in the film due to insufficient hydrolysis is eminent. Obviously, the chlorine residue in the HfO
₂
film is suspected to affect the quality of the HfO
₂
film. In this paper, The authors reduced the concentration of chlorine residues by increasing the H
₂
O oxidant pulse time in between the deposition cycles from 0.3 to 10 and 90 s. Time-of-flight secondary ion mass spectrometry analysis shows that this decreases the chlorine concentration in the HfO
₂
film by more than one order of magnitude. However, time-dependent dielectric breakdown analysis shows that the lifetime remains quasi unaffected (within identical error bars) for the different injection cycles. Charge pumping analysis was done by varying both pulse frequency and amplitude to investigate the creation of defects, but negligible differences were observed. Therefore, the presence of chlorine residues has no significant impact on the trap generation and reliability of ALD HfO
₂
layers, and this result corresponded with the mobility result. The experimental picture is confirmed with first-principle calculations that show that the presence of chlorine residues does not induce defect levels in the bandgap of HfO
₂