N. Zhan

Electrical characterization of the hafnium oxide prepared by direct sputtering of Hf in oxygen with rapid thermal annealing

Abstract Electrical characterization of the hafnium oxide (HfO 2 ) gate dielectric films prepared by Hf sputtering in oxygen was conducted. By measuring the current–voltage ( I – V ) characteristics at temperature ranging from 300 to 500 K, several abnormalities in the I – V characteristics are recorded. For temperatures below 400 K, the current–voltage characteristics in high field region can be plotted with the Fowler–Nordheim law but a stronger temperature dependence was observed. Large flatband voltage shifts in the Al/HfO 2 /Si capacitor were observed. The capacitance–voltage characteristics and flatband shifts are found to depend strongly on the post-deposition annealing temperature and duration. To study the reliability against high electric field, constant voltage stressing on the samples was conducted. We found that the trap energy levels are shallow and the oxide traps can be readily filled and detrapped at a low bias voltage.

Dielectric breakdown characteristics and interface trapping of hafnium oxide films

The breakdown characteristics of hafnium gate oxide prepared by direct sputtering with rapid thermal annealing are investigated in detail. We found that several soft breakdowns take place before a hard breakdown. Area and stress-voltage effects of the time-dependent dielectric breakdown are also observed. Results suggest that that the soft and hard breakdowns should have different precursor defects. A two-layer model of is proposed to explain these observations.

Characteristics of high quality hafnium oxide gate dielectric

Hafnium oxide (HfO/sub 2/) was investigated as an alternative possible gate dielectric. A MOS capacitor using HfO/sub 2/ as dielectric was fabricated and studied. The HfO/sub 2/ film was formed by direct sputtering of Hf in O/sub 2/ and Ar ambient on to a Si substrate and post-sputtering rapid thermal annealing (RTA). XPS results showed that the interface layer formed between the HfO/sub 2/ and the Si substrate was affected by the RTA time within the 500/spl deg/C to 600/spl deg/C annealing temperature. The interface layer was mainly composed of hafnium silicate and had high interface trap density. Increase in RTA time was found to lower the effective barrier height of the layer and the FN tunneling current.

Effects of rapid thermal annealing on the interface and oxide trap distributions in hafnium oxide films

The effects of rapid thermal annealing on the interface charge and oxide charge densities of sputtered hafnium oxide (HfO/sub 2/) films were investigated systematically. We found that both interface and oxide charge densities are strongly governed by the post-deposition annealing (PDA) conditions but have different dependencies. The interface trap density can be reduced by more than one order of magnitude to a value close to that of the Si/SiO/sub 2/ interface after proper (>600/spl deg/C) annealing. This effect is due to the formation of SiO/sub 2/ at the HfO/sub 2//Si interface. However, PDA has a negative impact on the oxide charge density. The PDA-induced oxide charge generation is attributed to the grain boundary interface states because of the crystallization of the HfO/sub 2/ at temperature greater than 650/spl deg/C.

Charge trapping and stress-induced dielectric breakdown characteristics of HfO/sub 2/ films

The reliability and integrity of HfO/sub 2/ prepared by sputtering were studied. By monitoring the current-voltage and current-stressing duration characteristics, we found that a significant charge trapping effect is found for very short stressing time (<30 s) but stress-induced trap generation is insignificant. Area and stress-voltage effects on the time-dependent dielectric breakdown (TDDB) were also studied. It was found that the Weibull shape factors for soft and hard breakdown are different and their values are 1.43 and 1.95, respectively. It suggests that the soft breakdown should have different precursor defects from those of the hard breakdown.

Electrical characteristics of novel hafnium oxide film

Hafnium oxide film grown by the direct sputtering of a hafnium target in oxygen ambient was investigated. XPS results showed that the interface between the hafnium oxide and silicon substrate was bad. The electrical characteristics of hafnium oxide and its interface layer were studied in detail by capacitance-voltage (C-V) and current-voltage (I-V) measurements. It was observed that the interface layer contains charge traps that affected the device operation.