以不同後沉積退火處理之原子層沉積HfO2閘極介質層C-V,I-V及應力作用後之行為

Abstract

In this thesis, we investigated the electrical properties and reliabilities of metal-oxide-semiconductor capacitors (MOSCs) with gate insulator made of atomic-layer-deposited (ALD) HfO2 high-k dielectrics prepared with N2, D2, and no post-deposition anneal (PDA). Both the capacitance-voltage (C-V) and current-voltage (I-V) characteristics were measured on MOSCs to determine the leakage current, hysteresis and interface trap density behaviors of those ALD HfO2 high-k dielectrics prepared with different PDAs. In this work, we also studied the breakdown failure distribution by applying ramped voltage stress (RVS) to the samples. From the C-V characteristics, flat-band voltage shift and counterclockwise hysteresises were found in the samples that subjected to N2 and D2 PDA. When compared with no PDA and N2 PDA samples, the D2 PDA sample shows minimal hysteresis. We also found that the ALD HfO2 after D2 PDA has the minimal gate leakage current from the I-V measurement data. This result implicates that PDA can reduce or passivate those pre-existing bulk traps in HfO2 gate dielectric by D2 PDA. For reliability study, both the constant voltage stress (CVS) as well as constant current stress (CCS) were applied to the samples. We found that the samples treated with D2 PDA exhibited smaller flat-band voltage shift and less interface traps density generation after CVS and CCS when compared with N2 and no PDA samples. The breakdown failure distribution also shows that the D2 PDA sample has the highest breakdown voltage among the three samples. These results indicate that D2 PDA can strengthen the interface bonding between the high-k dielectric and Si. We attribute these improvements to the formation of strong Si-D bonding near the interface provided by D2 annealing. We therefore conclude that D2 PDA can effectively improve the quality of ALD HfO2 high-k dielectric from the reliability point of view. Keyword: PDA, ALD, HfO2, C-V, and I-V