Characterization of pulsed laser deposited Al₂O₃ gate dielectric

The demands of future CMOS devices require a new gate dielectric material with higher dielectric constant than SiO2. Aluminum oxide is one of the high-k materials and an interesting candidate.Thin Al2O3 layers have been deposited by pulsed laser deposition (PLD) from a mono-crystalline sapphire target.This deposition technique was chosen because of its flexibility and availability. Aluminum oxide is known for its decent interface properties with silicon and is expected to be part of the future gate dielectric. The probability and effects of interface intermixing during PLD have been estimated by (thermodynamic) calculations. The results showed that the exchange of aluminum and silicon atoms at the interface is thermodynamically favourable. AFM and XPS analysis of PLD Al2O3 layers showed a difference in density and interface between samples deposited in Ar and O2. The films deposited in an Ar ambient appear to have a higher density and sharper Al2O3/Si interface.Test structures with PLD dielectric, thermal oxidation and jet vapor deposition (JVD) of SiO2 will be used to make a comparison between the layers and their interface properties.Electrical characterization will have to confirm the expected interface mixing, reduction in minority carrier mobility and effects of PLD deposition.