Leakage Current and Reliability on Planar High-k Capacitor with Al₂O₃ Dielectric Deposited by Thermal-ALD

Abstract

Due to its wide band-gap, Al₂O₃ is known to have a moderate leakage current and a good dielectric strength [1]. Moreover, this dielectric has a fair permittivity and so constitutes interesting candidate as dielectric for Metal-Insulator-Metal (MIM) capacitor. Atomic Layer Deposition (ALD) allows obtaining a dense and thin Al₂O₃ amorphous layer. ALD limits problems of interlayer diffusion because Al₂O₃ is deposited underneath 400°C [2] which is essential when MIM are co-integrated with temperature sensitive structures.

The aim of our investigation is to attempt to tie aluminum oxide properties dielectric with reliability from the help of capacitors of the entire wafer. In this way, conduction mechanism analysis and capacitance measurements were statistically led on the wafer. We particularly focus our study on the quantification of defects and their influence on the leakage current in planar capacitor. Firstly, to estimate the fixed oxide charges densities in the bulk of Al₂O₃ and to analyze conduction mechanism, Metal-Oxide-Semiconductor (MOS) (Al/Al₂O₃/HR-Si) is developed. Then, a MIM stack (Al/TiN/Al₂O₃/TiN/HR-Si) is developed in order to evaluate the leakage current and the electrical reliability of thin films Al₂O₃ based MIM capacitors. Different performances are observed according to the area on the wafer. That could be explained by the quality of the Al₂O₃ layer and the interfaces between TiN and the oxide.