Suppression of subcutaneous oxidation during the deposition of amorphous lanthanum aluminate on silicon

Abstract

Amorphous LaAlO3 thin films have been deposited by molecular beam deposition directly on silicon without detectable oxidation of the underlying substrate. We have studied these abrupt interfaces by Auger electron spectroscopy, high-resolution transmission electron microscopy, medium-energy ion scattering, transmission infrared absorption spectroscopy, and x-ray photoelectron spectroscopy. Together these techniques indicate that the films are fully oxidized and have less than 0.2 Å of SiO2 at the interface between the amorphous LaAlO3 and silicon. These heterostructures are being investigated for alternative gate dielectric applications and provide an opportunity to control the interface between the silicon and the gate dielectric.

Atomic Layer Deposition and Properties of Lanthanum Oxide and Lanthanum‐Aluminum Oxide Films

“…[10,22] The permittivity of lanthanum aluminate is in the range [22][23][24][25][26][27]. [20,[22][23][24][25] The bandgap of LaAlO 3 is 6.2 eV, [26] whilst band offsets on silicon are 1.8 eV for electrons and 3.2 eV for holes. [26] The reactivity of LaAlO 3 on silicon has also been studied.…”

“…[20,[22][23][24][25] The bandgap of LaAlO 3 is 6.2 eV, [26] whilst band offsets on silicon are 1.8 eV for electrons and 3.2 eV for holes. [26] The reactivity of LaAlO 3 on silicon has also been studied. [2,11] LaAlO 3 on Si may remain amorphous even after annealing.…”

High dielectric constant oxides

“…• C. LaAlO 3 passes most of the requirements [87]; it is also closely lattice matched to Si, La and Al oxides are both stable next to Si [153], they have low oxygen diffusion coefficients, and it has a conduction band offset of about 1.8 eV. Unfortunately, it has so far not been possible to grow LaAlO 3 crystals directly on Si, it grows amorphous.…”

Defect states in the high-dielectric-constant gate oxide LaAlO3

“…[10][11][12][13][14] Critically, LaAlO 3 has much lower atomic diffusion rates and less tendency to form the SiO 2 -based interfacial layer during processing. 15,16 Recently, amorphous LaAlO 3 gate stacks with an EOT of 0.3 nm have been achieved. 17 Crystalline LaAlO 3 ͑100͒ is lattice matched to Si͑100͒, with a 45°lattice rotation, and it could grow as an epitaxial oxide.…”