Al/HfO2/Si Gate Stack with Improved Physical and Electrical Parameters

In this paper, we present the fabrication and characterization of Al/HfO
₂
/Si gate stack with improved physical and electrical gate stack parameters such as dielectric constant (k), equivalent oxide thickness (EOT), interface trap density (Dit) and effective oxide charges (Qeff) extracted from the C-V and G-V characteristics. Atomic layer deposition (ALD) has been used for high-k dielectric formation. The effect of rapid thermal annealing (RTA) temperatures on the properties of the fabricated gate stack has also been investigated at 300 °C & 600 °C for 3 minutes in nitrogen (N
₂
) ambient whereas forming gas annealing (FGA) was performed at 420°C for 20 minutes in 96% N
₂
and 4% H
₂
ambient. Fourier transform infrared spectroscopy (FTIR) was used to study of thermal annealing effects on the HfO
₂
/Si interface. Filmetrics F20 thin film analyzer and XRD were used to find thickness and composition of the material respectively. The results reveal that the physical and electrical properties (K, Dit, Qeff, etc) have been improved by RTA in nitrogen ambient, which further improves the interface properties of HfO
₂
/Si due to the densification of HfO
₂
thin films. It is also shown that the 600°C nitrogen annealed samples exhibit a reduced EOT 2.54 nm, interfacial trap density, effective oxide charges (Qeff), C - V hysteresis and leakage current.